]> git.saurik.com Git - apple/xnu.git/blobdiff - osfmk/ipc/ipc_importance.c
xnu-4570.41.2.tar.gz
[apple/xnu.git] / osfmk / ipc / ipc_importance.c
index a8aa9c4005a807af1122b2220801a5538f81cd32..f89005cf35632a3e26348542bd306026a3f96767 100644 (file)
@@ -40,6 +40,7 @@
 #include <kern/zalloc.h>
 #include <kern/queue.h>
 #include <kern/task.h>
+#include <kern/policy_internal.h>
 
 #include <sys/kdebug.h>
 
@@ -83,6 +84,8 @@ static lck_spin_t ipc_importance_lock_data;   /* single lock for now */
        lck_spin_try_lock(&ipc_importance_lock_data)
 #define        ipc_importance_unlock() \
        lck_spin_unlock(&ipc_importance_lock_data)
+#define ipc_importance_assert_held() \
+       lck_spin_assert(&ipc_importance_lock_data, LCK_ASSERT_OWNED)
 #define ipc_importance_sleep(elem) lck_spin_sleep(&ipc_importance_lock_data,   \
                                        LCK_SLEEP_DEFAULT,                      \
                                        (event_t)(elem),                        \
@@ -160,6 +163,14 @@ static zone_t ipc_importance_inherit_zone;
 
 static ipc_voucher_attr_control_t ipc_importance_control;
 
+static boolean_t ipc_importance_task_check_transition(ipc_importance_task_t task_imp,
+       iit_update_type_t type, uint32_t delta);
+
+static void ipc_importance_task_propagate_assertion_locked(ipc_importance_task_t task_imp,
+       iit_update_type_t type, boolean_t update_task_imp);
+
+static ipc_importance_inherit_t ipc_importance_inherit_from_task(task_t from_task, task_t to_task);
+
 /*
  *     Routine:        ipc_importance_kmsg_link
  *     Purpose:
@@ -236,18 +247,53 @@ ipc_importance_inherit_link(
        ipc_importance_inherit_t inherit,
        ipc_importance_elem_t elem)
 {
-       ipc_importance_elem_t link_elem;
+       ipc_importance_task_t link_task;
 
        assert(IIE_NULL == inherit->iii_from_elem);
-       link_elem = (IIE_TYPE_INHERIT == IIE_TYPE(elem)) ?
-               (ipc_importance_elem_t)((ipc_importance_inherit_t)elem)->iii_to_task :
-               elem;
+       link_task = (IIE_TYPE_INHERIT == IIE_TYPE(elem)) ?
+               ((ipc_importance_inherit_t)elem)->iii_to_task :
+               (ipc_importance_task_t)elem;
 
-       queue_enter(&link_elem->iie_inherits, inherit, 
+       queue_enter(&link_task->iit_inherits, inherit, 
                    ipc_importance_inherit_t, iii_inheritance);
        inherit->iii_from_elem = elem;
 }
 
+/*
+ *     Routine:        ipc_importance_inherit_find
+ *     Purpose:
+ *             Find an existing inherit that links the from element to the
+ *             to_task at a given nesting depth.  As inherits from other
+ *             inherits are actually linked off the original inherit's donation
+ *             receiving task, we have to conduct our search from there if
+ *             the from element is an inherit.
+ *     Returns:
+ *             A pointer (not a reference) to the matching inherit.
+ *     Conditions:
+ *             Importance lock held.
+ */
+static ipc_importance_inherit_t
+ipc_importance_inherit_find(
+       ipc_importance_elem_t from,
+       ipc_importance_task_t to_task,
+       unsigned int depth)
+{
+       ipc_importance_task_t link_task;
+       ipc_importance_inherit_t inherit;
+
+       link_task = (IIE_TYPE_INHERIT == IIE_TYPE(from)) ?
+               ((ipc_importance_inherit_t)from)->iii_to_task :
+               (ipc_importance_task_t)from;
+
+       queue_iterate(&link_task->iit_inherits, inherit,
+                     ipc_importance_inherit_t, iii_inheritance) {
+               if (inherit->iii_to_task == to_task && inherit->iii_depth == depth) {
+                       return inherit;
+               }
+       }
+       return III_NULL;
+}
+
 /*
  *     Routine:        ipc_importance_inherit_unlink
  *     Purpose:
@@ -268,13 +314,13 @@ ipc_importance_inherit_unlink(
        ipc_importance_elem_t elem = inherit->iii_from_elem;
 
        if (IIE_NULL != elem) {
-               ipc_importance_elem_t unlink_elem;
+               ipc_importance_task_t unlink_task;
 
-               unlink_elem = (IIE_TYPE_INHERIT == IIE_TYPE(elem)) ?
-                       (ipc_importance_elem_t)((ipc_importance_inherit_t)elem)->iii_to_task : 
-                       elem;
+               unlink_task = (IIE_TYPE_INHERIT == IIE_TYPE(elem)) ?
+                       ((ipc_importance_inherit_t)elem)->iii_to_task : 
+                       (ipc_importance_task_t)elem;
 
-               queue_remove(&unlink_elem->iie_inherits, inherit, 
+               queue_remove(&unlink_task->iit_inherits, inherit, 
                             ipc_importance_inherit_t, iii_inheritance);
                inherit->iii_from_elem = IIE_NULL;
        }
@@ -308,40 +354,36 @@ ipc_importance_release_locked(ipc_importance_elem_t elem)
 {
        assert(0 < IIE_REFS(elem));
 
-       if (0 < ipc_importance_release_internal(elem)) {
-
-#if DEVELOPMENT || DEBUG
-               ipc_importance_inherit_t temp_inherit;
-               ipc_importance_task_t link_task;
-               ipc_kmsg_t temp_kmsg;
-               uint32_t expected = 0;
-
-               if (0 < elem->iie_made)
-                       expected++;
-
-               link_task = (IIE_TYPE_INHERIT == IIE_TYPE(elem)) ?
-                       ((ipc_importance_inherit_t)elem)->iii_to_task : 
-                       (ipc_importance_task_t)elem;
-
-               queue_iterate(&link_task->iit_kmsgs, temp_kmsg, ipc_kmsg_t, ikm_inheritance)
-                       if (temp_kmsg->ikm_importance == elem)
-                               expected++;
-               queue_iterate(&link_task->iit_inherits, temp_inherit,
-                             ipc_importance_inherit_t, iii_inheritance)
-                       if (temp_inherit->iii_from_elem == elem)
-                               expected++;
+#if IMPORTANCE_DEBUG
+       ipc_importance_inherit_t temp_inherit;
+       ipc_importance_task_t link_task;
+       ipc_kmsg_t temp_kmsg;
+       uint32_t expected = 0;
+
+       if (0 < elem->iie_made)
+               expected++;
+
+       link_task = (IIE_TYPE_INHERIT == IIE_TYPE(elem)) ?
+               ((ipc_importance_inherit_t)elem)->iii_to_task : 
+               (ipc_importance_task_t)elem;
+
+       queue_iterate(&link_task->iit_kmsgs, temp_kmsg, ipc_kmsg_t, ikm_inheritance)
+               if (temp_kmsg->ikm_importance == elem)
+                       expected++;
+       queue_iterate(&link_task->iit_inherits, temp_inherit,
+                     ipc_importance_inherit_t, iii_inheritance)
+               if (temp_inherit->iii_from_elem == elem)
+                       expected++;
+       if (IIE_REFS(elem) < expected + 1)
+               panic("ipc_importance_release_locked (%p)", elem);
+#endif /* IMPORTANCE_DEBUG */
 
-               if (IIE_REFS(elem) < expected)
-                       panic("ipc_importance_release_locked (%p)", elem);
-#endif
+       if (0 < ipc_importance_release_internal(elem)) {
                ipc_importance_unlock();
                return;
        }
 
        /* last ref */
-       /* can't get to no refs if we contribute to something else's importance */
-       assert(queue_empty(&elem->iie_kmsgs));
-       assert(queue_empty(&elem->iie_inherits));
 
        switch (IIE_TYPE(elem)) {
 
@@ -351,6 +393,8 @@ ipc_importance_release_locked(ipc_importance_elem_t elem)
                ipc_importance_task_t task_elem;
 
                task_elem = (ipc_importance_task_t)elem;
+
+               /* the task can't still hold a reference on the task importance */
                assert(TASK_NULL == task_elem->iit_task);
 
 #if DEVELOPMENT || DEBUG
@@ -366,25 +410,63 @@ ipc_importance_release_locked(ipc_importance_elem_t elem)
        /* dropping an inherit element */
        case IIE_TYPE_INHERIT:
        {
-               ipc_importance_inherit_t inherit;
+               ipc_importance_inherit_t inherit = (ipc_importance_inherit_t)elem;
+               ipc_importance_task_t to_task = inherit->iii_to_task;
                ipc_importance_elem_t from_elem;
-               ipc_importance_task_t to_task;
 
-
-               inherit = (ipc_importance_inherit_t)elem;
-               to_task = inherit->iii_to_task;
                assert(IIT_NULL != to_task);
-               assert(!inherit->iii_donating);
-
-               /* unlink and release the inherit */
                assert(ipc_importance_task_is_any_receiver_type(to_task));
+
+               /* unlink the inherit from its source element */
                from_elem = ipc_importance_inherit_unlink(inherit);
                assert(IIE_NULL != from_elem);
+
+               /*
+                * The attribute might have pending external boosts if the attribute
+                * was given out during exec, drop them from the appropriate destination
+                * task.
+                *
+                * The attribute will not have any pending external boosts if the
+                * attribute was given out to voucher system since it would have been
+                * dropped by ipc_importance_release_value, but there is not way to
+                * detect that, thus if the attribute has a pending external boost,
+                * drop them from the appropriate destination task.
+                *
+                * The inherit attribute from exec and voucher system would not
+                * get deduped to each other, thus dropping the external boost
+                * from destination task at two different places will not have
+                * any unintended side effects.
+                */
+               assert(inherit->iii_externcnt >= inherit->iii_externdrop);
+               if (inherit->iii_donating) {
+                       uint32_t assertcnt = III_EXTERN(inherit);
+
+                       assert(ipc_importance_task_is_any_receiver_type(to_task));
+                       assert(to_task->iit_externcnt >= inherit->iii_externcnt);
+                       assert(to_task->iit_externdrop >= inherit->iii_externdrop);
+                       to_task->iit_externcnt -= inherit->iii_externcnt;
+                       to_task->iit_externdrop -= inherit->iii_externdrop;
+                       inherit->iii_externcnt = 0;
+                       inherit->iii_externdrop = 0;
+                       inherit->iii_donating = FALSE;
+
+                       /* adjust the internal assertions - and propagate as needed */
+                       if (ipc_importance_task_check_transition(to_task, IIT_UPDATE_DROP, assertcnt)) {
+                               ipc_importance_task_propagate_assertion_locked(to_task, IIT_UPDATE_DROP, TRUE);
+                       }
+               } else {
+                       inherit->iii_externcnt = 0;
+                       inherit->iii_externdrop = 0;
+               }
+
+               /* release the reference on the source element */
                ipc_importance_release_locked(from_elem);
                /* unlocked on return */
 
+               /* release the reference on the destination task */
                ipc_importance_task_release(to_task);
 
+               /* free the inherit */
                zfree(ipc_importance_inherit_zone, inherit);
                break;
        }
@@ -510,16 +592,19 @@ ipc_importance_task_check_transition(
        iit_update_type_t type,
        uint32_t delta)
 {
-
+#if IMPORTANCE_TRACE
        task_t target_task = task_imp->iit_task;
+#endif
        boolean_t boost = (IIT_UPDATE_HOLD == type);
        boolean_t before_boosted, after_boosted;
 
+       ipc_importance_assert_held();
+
        if (!ipc_importance_task_is_any_receiver_type(task_imp))
                return FALSE;
 
-#if IMPORTANCE_DEBUG
-       int target_pid = (TASK_NULL != target_task) ? audit_token_pid_from_task(target_task) : -1;
+#if IMPORTANCE_TRACE
+       int target_pid = task_pid(target_task);
 
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (IMPORTANCE_CODE(IMP_ASSERTION, (((boost) ? IMP_HOLD : IMP_DROP) | TASK_POLICY_INTERNAL))) | DBG_FUNC_START,
                                          proc_selfpid(), target_pid, task_imp->iit_assertcnt, IIT_EXTERN(task_imp), 0);
@@ -531,34 +616,25 @@ ipc_importance_task_check_transition(
        /* Adjust the assertcnt appropriately */
        if (boost) {
                task_imp->iit_assertcnt += delta;
-#if IMPORTANCE_DEBUG
+#if IMPORTANCE_TRACE
         DTRACE_BOOST6(send_boost, task_t, target_task, int, target_pid,
                       task_t, current_task(), int, proc_selfpid(), int, delta, int, task_imp->iit_assertcnt);
 #endif
        } else {
                // assert(delta <= task_imp->iit_assertcnt);
-               if (delta > task_imp->iit_assertcnt - IIT_EXTERN(task_imp)) {
+               if (task_imp->iit_assertcnt < delta + IIT_EXTERN(task_imp)) {
                        /* TODO: Turn this back into a panic <rdar://problem/12592649> */
-                       if (target_task != TASK_NULL) {
-                               printf("Over-release of kernel-internal importance assertions for pid %d (%s), "
-                                      "dropping %d assertion(s) but task only has %d remaining (%d external).\n",
-                                      audit_token_pid_from_task(target_task),
-                                      (target_task->bsd_info == NULL) ? "" : proc_name_address(target_task->bsd_info),
-                                      delta,
-                                      task_imp->iit_assertcnt,
-                                      IIT_EXTERN(task_imp));
-                       }
                        task_imp->iit_assertcnt = IIT_EXTERN(task_imp);
                } else {
                        task_imp->iit_assertcnt -= delta;
                }
-#if IMPORTANCE_DEBUG
+#if IMPORTANCE_TRACE
                // This convers both legacy and voucher-based importance.
                DTRACE_BOOST4(drop_boost, task_t, target_task, int, target_pid, int, delta, int, task_imp->iit_assertcnt);
 #endif
        }
 
-#if IMPORTANCE_DEBUG
+#if IMPORTANCE_TRACE
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (IMPORTANCE_CODE(IMP_ASSERTION, (((boost) ? IMP_HOLD : IMP_DROP) | TASK_POLICY_INTERNAL))) | DBG_FUNC_END,
                                  proc_selfpid(), target_pid, task_imp->iit_assertcnt, IIT_EXTERN(task_imp), 0);
 #endif
@@ -653,7 +729,7 @@ ipc_importance_task_propagate_helper(
                assert(IP_VALID(port));
                ip_lock(port);
                temp_task_imp = IIT_NULL;
-               if (!ipc_port_importance_delta_internal(port, &delta, &temp_task_imp)) {
+               if (!ipc_port_importance_delta_internal(port, IPID_OPTION_NORMAL, &delta, &temp_task_imp)) {
                        ip_unlock(port);
                }
 
@@ -666,7 +742,7 @@ ipc_importance_task_propagate_helper(
 
                /* Adjust the task assertions and determine if an edge was crossed */
                if (ipc_importance_task_check_transition(temp_task_imp, type, 1)) {
-                       incr_ref_counter(task_imp->iit_elem.iie_task_refs_added_transition);
+                       incr_ref_counter(temp_task_imp->iit_elem.iie_task_refs_added_transition);
                        queue_enter(propagation, temp_task_imp, ipc_importance_task_t, iit_props);
                        /* reference donated */
                } else {
@@ -731,7 +807,7 @@ ipc_importance_task_propagate_helper(
                assert(ipc_importance_task_is_any_receiver_type(temp_task_imp));
                if (ipc_importance_task_check_transition(temp_task_imp, type, assertcnt)) {
                        ipc_importance_task_reference(temp_task_imp);
-                       incr_ref_counter(task_imp->iit_elem.iie_task_refs_added_transition);
+                       incr_ref_counter(temp_task_imp->iit_elem.iie_task_refs_added_transition);
                        queue_enter(propagation, temp_task_imp, ipc_importance_task_t, iit_props);
                } 
        }
@@ -864,7 +940,7 @@ ipc_importance_task_process_updates(
                /* complete the policy update with the task unlocked */
                ipc_importance_task_release(task_imp);
                task_unlock(target_task);
-               task_policy_update_complete_unlocked(target_task, THREAD_NULL, &pend_token);
+               task_policy_update_complete_unlocked(target_task, &pend_token);
                task_deallocate(target_task);
 
                ipc_importance_lock();
@@ -1007,12 +1083,16 @@ ipc_importance_task_propagate_assertion_locked(
        queue_init(&updates);
        queue_init(&propagate);
 
+       ipc_importance_assert_held();
+
        /*
         * If we're going to update the policy for the provided task,
         * enqueue it on the propagate queue itself.  Otherwise, only
         * enqueue downstream things.
         */
        if (update_task_imp) {
+               ipc_importance_task_reference(task_imp);
+               incr_ref_counter(task_imp->iit_elem.iie_task_refs_added_transition);
                queue_enter(&propagate, task_imp, ipc_importance_task_t, iit_props);
        } else {
                ipc_importance_task_propagate_helper(task_imp, type, &propagate);
@@ -1026,6 +1106,8 @@ ipc_importance_task_propagate_assertion_locked(
                boolean_t need_update;
 
                queue_remove_first(&propagate, temp_task_imp, ipc_importance_task_t, iit_props);
+               /* hold a reference on temp_task_imp */
+
                assert(IIT_NULL != temp_task_imp);
 
                /* only propagate for receivers not already marked as a donor */
@@ -1039,22 +1121,36 @@ ipc_importance_task_propagate_assertion_locked(
                temp_task_imp->iit_updatepolicy = 0;
                if (need_update && TASK_NULL != temp_task_imp->iit_task) {
                        if (NULL == temp_task_imp->iit_updateq) {
-                               temp_task_imp->iit_updatetime = 0;
-                               temp_task_imp->iit_updateq = &updates;
-                               ipc_importance_task_reference_internal(temp_task_imp);
-                               if (boost) {
-                                       queue_enter(&updates, temp_task_imp,
-                                                   ipc_importance_task_t, iit_updates);
+
+                               /*
+                                * If a downstream task that needs an update is subjects to AppNap,
+                                * drop boosts according to the delay hysteresis.  Otherwise,
+                                * immediate update it.
+                                */
+                               if (!boost && temp_task_imp != task_imp &&
+                                   ipc_importance_delayed_drop_call != NULL &&
+                                   ipc_importance_task_is_marked_denap_receiver(temp_task_imp)) {
+                                       ipc_importance_task_delayed_drop(temp_task_imp);
                                } else {
-                                       queue_enter_first(&updates, temp_task_imp,
-                                                         ipc_importance_task_t, iit_updates);
+                                       temp_task_imp->iit_updatetime = 0;
+                                       temp_task_imp->iit_updateq = &updates;
+                                       ipc_importance_task_reference_internal(temp_task_imp);
+                                       if (boost) {
+                                               queue_enter(&updates, temp_task_imp,
+                                                           ipc_importance_task_t, iit_updates);
+                                       } else {
+                                               queue_enter_first(&updates, temp_task_imp,
+                                                                 ipc_importance_task_t, iit_updates);
+                                       }
                                }
                        } else {
                                /* Must already be on the AppNap hysteresis queue */
-                               assert(&ipc_importance_delayed_drop_queue);
+                               assert(ipc_importance_delayed_drop_call != NULL);
                                assert(ipc_importance_task_is_marked_denap_receiver(temp_task_imp));
                        }       
                }
+
+               ipc_importance_task_release_internal(temp_task_imp);
        }
 
        /* apply updates to task (may drop importance lock) */
@@ -1241,8 +1337,8 @@ ipc_importance_task_hold_legacy_external_assertion(ipc_importance_task_t task_im
        ipc_importance_lock();
        target_task = task_imp->iit_task;
 
-#if IMPORTANCE_DEBUG
-       int target_pid = (TASK_NULL != target_task) ? audit_token_pid_from_task(target_task) : -1;
+#if IMPORTANCE_TRACE
+       int target_pid = task_pid(target_task);
 
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (IMPORTANCE_CODE(IMP_ASSERTION, (IMP_HOLD | TASK_POLICY_EXTERNAL))) | DBG_FUNC_START,
                proc_selfpid(), target_pid, task_imp->iit_assertcnt, IIT_LEGACY_EXTERN(task_imp), 0);
@@ -1267,7 +1363,7 @@ ipc_importance_task_hold_legacy_external_assertion(ipc_importance_task_t task_im
        }
        ipc_importance_unlock();
 
-#if IMPORTANCE_DEBUG
+#if IMPORTANCE_TRACE
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (IMPORTANCE_CODE(IMP_ASSERTION, (IMP_HOLD | TASK_POLICY_EXTERNAL))) | DBG_FUNC_END,
                                  proc_selfpid(), target_pid, task_imp->iit_assertcnt, IIT_LEGACY_EXTERN(task_imp), 0);
         // This covers the legacy case where a task takes an extra boost.
@@ -1278,7 +1374,7 @@ ipc_importance_task_hold_legacy_external_assertion(ipc_importance_task_t task_im
                printf("BUG in process %s[%d]: "
                       "attempt to acquire an additional legacy external boost assertion without holding an existing legacy external assertion. "
                       "(%d total, %d external, %d legacy-external)\n",
-                      proc_name_address(target_task->bsd_info), audit_token_pid_from_task(target_task),
+                      proc_name_address(target_task->bsd_info), task_pid(target_task),
                       target_assertcnt, target_externcnt, target_legacycnt);
        }
 
@@ -1315,8 +1411,8 @@ ipc_importance_task_drop_legacy_external_assertion(ipc_importance_task_t task_im
        ipc_importance_lock();
        target_task = task_imp->iit_task;
 
-#if IMPORTANCE_DEBUG
-       int target_pid = (TASK_NULL != target_task) ? audit_token_pid_from_task(target_task) : -1;
+#if IMPORTANCE_TRACE
+       int target_pid = task_pid(target_task);
 
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (IMPORTANCE_CODE(IMP_ASSERTION, (IMP_DROP | TASK_POLICY_EXTERNAL))) | DBG_FUNC_START,
                proc_selfpid(), target_pid, task_imp->iit_assertcnt, IIT_LEGACY_EXTERN(task_imp), 0);
@@ -1360,7 +1456,7 @@ ipc_importance_task_drop_legacy_external_assertion(ipc_importance_task_t task_im
                ret = KERN_SUCCESS;
        }
 
-#if IMPORTANCE_DEBUG
+#if IMPORTANCE_TRACE
                KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (IMPORTANCE_CODE(IMP_ASSERTION, (IMP_DROP | TASK_POLICY_EXTERNAL))) | DBG_FUNC_END,
                                          proc_selfpid(), target_pid, task_imp->iit_assertcnt, IIT_LEGACY_EXTERN(task_imp), 0);
 #endif
@@ -1370,7 +1466,7 @@ ipc_importance_task_drop_legacy_external_assertion(ipc_importance_task_t task_im
        /* delayed printf for user-supplied data failures */
        if (KERN_FAILURE == ret && TASK_NULL != target_task) {
                printf("BUG in process %s[%d]: over-released legacy external boost assertions (%d total, %d external, %d legacy-external)\n",
-                      proc_name_address(target_task->bsd_info), audit_token_pid_from_task(target_task),
+                      proc_name_address(target_task->bsd_info), task_pid(target_task),
                       target_assertcnt, target_externcnt, target_legacycnt);
        }
 
@@ -1393,8 +1489,8 @@ ipc_importance_task_externalize_legacy_assertion(ipc_importance_task_t task_imp,
                return KERN_FAILURE;
        }
 
-#if IMPORTANCE_DEBUG
-       int target_pid = audit_token_pid_from_task(target_task);
+#if IMPORTANCE_TRACE
+       int target_pid = task_pid(target_task);
 
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (IMPORTANCE_CODE(IMP_ASSERTION, IMP_EXTERN)) | DBG_FUNC_START,
                proc_selfpid(), target_pid, task_imp->iit_assertcnt, IIT_EXTERN(task_imp), 0);
@@ -1407,12 +1503,12 @@ ipc_importance_task_externalize_legacy_assertion(ipc_importance_task_t task_imp,
        task_imp->iit_externcnt += count;
        ipc_importance_unlock();
 
-#if IMPORTANCE_DEBUG
+#if IMPORTANCE_TRACE
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (IMPORTANCE_CODE(IMP_ASSERTION, IMP_EXTERN)) | DBG_FUNC_END,
                                  proc_selfpid(), target_pid, task_imp->iit_assertcnt, IIT_LEGACY_EXTERN(task_imp), 0);
     // This is the legacy boosting path
        DTRACE_BOOST5(receive_boost, task_t, target_task, int, target_pid, int, sender_pid, int, count, int, IIT_LEGACY_EXTERN(task_imp));
-#endif /* IMPORTANCE_DEBUG */
+#endif /* IMPORTANCE_TRACE */
 
        return(KERN_SUCCESS);
 }
@@ -1455,10 +1551,10 @@ ipc_importance_task_update_live_donor(ipc_importance_task_t task_imp)
        before_donor = ipc_importance_task_is_marked_donor(task_imp);
 
        /* snapshot task live donor status - may change, but another call will accompany the change */
-       task_live_donor = target_task->effective_policy.t_live_donor;
+       task_live_donor = target_task->effective_policy.tep_live_donor;
 
-#if IMPORTANCE_DEBUG
-       int target_pid = audit_token_pid_from_task(target_task);
+#if IMPORTANCE_TRACE
+       int target_pid = task_pid(target_task);
 
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
                                  (IMPORTANCE_CODE(IMP_DONOR_CHANGE, IMP_DONOR_UPDATE_LIVE_DONOR_STATE)) | DBG_FUNC_START,
@@ -1484,7 +1580,7 @@ ipc_importance_task_update_live_donor(ipc_importance_task_t task_imp)
                ipc_importance_task_propagate_assertion_locked(task_imp, type, FALSE);
        }
 
-#if IMPORTANCE_DEBUG
+#if IMPORTANCE_TRACE
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
                                  (IMPORTANCE_CODE(IMP_DONOR_CHANGE, IMP_DONOR_UPDATE_LIVE_DONOR_STATE)) | DBG_FUNC_END,
                                  target_pid, task_imp->iit_donor, task_live_donor, after_donor, 0);
@@ -1520,7 +1616,7 @@ ipc_importance_task_mark_donor(ipc_importance_task_t task_imp, boolean_t donatin
 
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
                                  (IMPORTANCE_CODE(IMP_DONOR_CHANGE, IMP_DONOR_INIT_DONOR_STATE)) | DBG_FUNC_NONE,
-                                 audit_token_pid_from_task(task_imp->iit_task), donating,
+                                 task_pid(task_imp->iit_task), donating,
                                  old_donor, task_imp->iit_donor, 0);
        
        ipc_importance_unlock();
@@ -1901,7 +1997,7 @@ void task_importance_update_owner_info(task_t task) {
        if (task != TASK_NULL && task->task_imp_base != IIT_NULL) {
                ipc_importance_task_t task_elem = task->task_imp_base;
 
-               task_elem->iit_bsd_pid = audit_token_pid_from_task(task);
+               task_elem->iit_bsd_pid = task_pid(task);
                if (task->bsd_info) {
                        strncpy(&task_elem->iit_procname[0], proc_name_address(task->bsd_info), 16);
                        task_elem->iit_procname[16] = '\0';
@@ -1940,11 +2036,10 @@ ipc_importance_reset_locked(ipc_importance_task_t task_imp, boolean_t donor)
        task_imp->iit_externdrop -= task_imp->iit_legacy_externdrop;
 
        /* assert(IIT_LEGACY_EXTERN(task_imp) <= task_imp->iit_assertcnt); */
-       if (IIT_LEGACY_EXTERN(task_imp) < task_imp->iit_assertcnt) {
+       if (IIT_EXTERN(task_imp) < task_imp->iit_assertcnt) {
                task_imp->iit_assertcnt -= IIT_LEGACY_EXTERN(task_imp);
        } else {
-               assert(IIT_LEGACY_EXTERN(task_imp) == task_imp->iit_assertcnt);
-               task_imp->iit_assertcnt = 0;
+               task_imp->iit_assertcnt = IIT_EXTERN(task_imp);
        }
        task_imp->iit_legacy_externcnt = 0;
        task_imp->iit_legacy_externdrop = 0;
@@ -2033,6 +2128,344 @@ ipc_importance_disconnect_task(task_t task)
        task_deallocate(task);
 }
 
+/*
+ *     Routine:        ipc_importance_exec_switch_task
+ *     Purpose:
+ *             Switch importance task base from old task to new task in exec.
+ *
+ *             Create an ipc importance linkage from old task to new task,
+ *             once the linkage is created, switch the importance task base
+ *             from old task to new task. After the switch, the linkage will
+ *             represent importance linkage from new task to old task with
+ *             watch port importance inheritance linked to new task.
+ *     Conditions:
+ *             Nothing locked.
+ *             Returns a reference on importance inherit.
+ */
+ipc_importance_inherit_t
+ipc_importance_exec_switch_task(
+       task_t old_task,
+       task_t new_task)
+{
+       ipc_importance_inherit_t inherit = III_NULL;
+       ipc_importance_task_t old_task_imp = IIT_NULL;
+       ipc_importance_task_t new_task_imp = IIT_NULL;
+
+       task_importance_reset(old_task);
+
+       /* Create an importance linkage from old_task to new_task */
+       inherit = ipc_importance_inherit_from_task(old_task, new_task);
+       if (inherit == III_NULL) {
+               return inherit;
+       }
+
+       /* Switch task importance base from old task to new task */
+       ipc_importance_lock();
+
+       old_task_imp = old_task->task_imp_base;
+       new_task_imp = new_task->task_imp_base;
+
+       old_task_imp->iit_task = new_task;
+       new_task_imp->iit_task = old_task;
+
+       old_task->task_imp_base = new_task_imp;
+       new_task->task_imp_base = old_task_imp;
+
+#if DEVELOPMENT || DEBUG
+       /*
+        * Update the pid an proc name for importance base if any
+        */
+       task_importance_update_owner_info(new_task);
+#endif
+       ipc_importance_unlock();
+
+       return inherit;
+}
+
+/*
+ *     Routine:        ipc_importance_check_circularity
+ *     Purpose:
+ *             Check if queueing "port" in a message for "dest"
+ *             would create a circular group of ports and messages.
+ *
+ *             If no circularity (FALSE returned), then "port"
+ *             is changed from "in limbo" to "in transit".
+ *
+ *             That is, we want to set port->ip_destination == dest,
+ *             but guaranteeing that this doesn't create a circle
+ *             port->ip_destination->ip_destination->... == port
+ *
+ *             Additionally, if port was successfully changed to "in transit",
+ *             propagate boost assertions from the "in limbo" port to all
+ *             the ports in the chain, and, if the destination task accepts
+ *             boosts, to the destination task.
+ *
+ *     Conditions:
+ *             No ports locked.  References held for "port" and "dest".
+ */
+
+boolean_t
+ipc_importance_check_circularity(
+       ipc_port_t      port,
+       ipc_port_t      dest)
+{
+       ipc_importance_task_t imp_task = IIT_NULL;
+       ipc_importance_task_t release_imp_task = IIT_NULL;
+       boolean_t imp_lock_held = FALSE;
+       int assertcnt = 0;
+       ipc_port_t base;
+       sync_qos_count_t sync_qos_delta_add[THREAD_QOS_LAST] = {0};
+       sync_qos_count_t sync_qos_delta_sub[THREAD_QOS_LAST] = {0};
+       boolean_t update_knote = FALSE;
+
+       assert(port != IP_NULL);
+       assert(dest != IP_NULL);
+
+       if (port == dest)
+               return TRUE;
+       base = dest;
+
+       /* port is in limbo, so donation status is safe to latch */
+       if (port->ip_impdonation != 0) {
+               imp_lock_held = TRUE;
+               ipc_importance_lock();
+       }
+
+       /*
+        *      First try a quick check that can run in parallel.
+        *      No circularity if dest is not in transit.
+        */
+       ip_lock(port);
+
+       /* 
+        * Even if port is just carrying assertions for others,
+        * we need the importance lock.
+        */
+       if (port->ip_impcount > 0 && !imp_lock_held) {
+               if (!ipc_importance_lock_try()) {
+                       ip_unlock(port);
+                       ipc_importance_lock();
+                       ip_lock(port);
+               }
+               imp_lock_held = TRUE;
+       }
+
+       if (ip_lock_try(dest)) {
+               if (!ip_active(dest) ||
+                   (dest->ip_receiver_name != MACH_PORT_NULL) ||
+                   (dest->ip_destination == IP_NULL))
+                       goto not_circular;
+
+               /* dest is in transit; further checking necessary */
+
+               ip_unlock(dest);
+       }
+       ip_unlock(port);
+
+       /* 
+        * We're about to pay the cost to serialize,
+        * just go ahead and grab importance lock.
+        */
+       if (!imp_lock_held) {
+               ipc_importance_lock();
+               imp_lock_held = TRUE;
+       }
+
+       ipc_port_multiple_lock(); /* massive serialization */
+
+       /*
+        *      Search for the end of the chain (a port not in transit),
+        *      acquiring locks along the way.
+        */
+
+       for (;;) {
+               ip_lock(base);
+
+               if (!ip_active(base) ||
+                   (base->ip_receiver_name != MACH_PORT_NULL) ||
+                   (base->ip_destination == IP_NULL))
+                       break;
+
+               base = base->ip_destination;
+       }
+
+       /* all ports in chain from dest to base, inclusive, are locked */
+
+       if (port == base) {
+               /* circularity detected! */
+
+               ipc_port_multiple_unlock();
+
+               /* port (== base) is in limbo */
+
+               assert(ip_active(port));
+               assert(port->ip_receiver_name == MACH_PORT_NULL);
+               assert(port->ip_destination == IP_NULL);
+
+               while (dest != IP_NULL) {
+                       ipc_port_t next;
+
+                       /* dest is in transit or in limbo */
+
+                       assert(ip_active(dest));
+                       assert(dest->ip_receiver_name == MACH_PORT_NULL);
+
+                       next = dest->ip_destination;
+                       ip_unlock(dest);
+                       dest = next;
+               }
+
+               if (imp_lock_held)
+                       ipc_importance_unlock();
+
+               return TRUE;
+       }
+
+       /*
+        *      The guarantee:  lock port while the entire chain is locked.
+        *      Once port is locked, we can take a reference to dest,
+        *      add port to the chain, and unlock everything.
+        */
+
+       ip_lock(port);
+       ipc_port_multiple_unlock();
+
+not_circular:
+       imq_lock(&base->ip_messages);
+
+       /* port is in limbo */
+
+       assert(ip_active(port));
+       assert(port->ip_receiver_name == MACH_PORT_NULL);
+       assert(port->ip_destination == IP_NULL);
+
+       ip_reference(dest);
+       port->ip_destination = dest;
+
+       /* must have been in limbo or still bound to a task */
+       assert(port->ip_tempowner != 0);
+
+       /*
+        * We delayed dropping assertions from a specific task.
+        * Cache that info now (we'll drop assertions and the
+        * task reference below).
+        */
+       release_imp_task = port->ip_imp_task;
+       if (IIT_NULL != release_imp_task) {
+               port->ip_imp_task = IIT_NULL;
+       }
+       assertcnt = port->ip_impcount;
+
+       /* take the port out of limbo w.r.t. assertions */
+       port->ip_tempowner = 0;
+
+       /* Capture the sync qos count delta */
+       for (int i = 0; i < THREAD_QOS_LAST; i++) {
+               sync_qos_delta_add[i] = port_sync_qos(port, i);
+       }
+
+       /* now unlock chain */
+
+       ip_unlock(port);
+
+       for (;;) {
+
+               /* every port along chain track assertions behind it */
+               ipc_port_impcount_delta(dest, assertcnt, base);
+               update_knote = ipc_port_sync_qos_delta(dest, sync_qos_delta_add, sync_qos_delta_sub);
+
+               if (dest == base)
+                       break;
+
+               /* port is in transit */
+
+               assert(ip_active(dest));
+               assert(dest->ip_receiver_name == MACH_PORT_NULL);
+               assert(dest->ip_destination != IP_NULL);
+               assert(dest->ip_tempowner == 0);
+
+               port = dest->ip_destination;
+               ip_unlock(dest);
+               dest = port;
+       }
+
+       /* base is not in transit */
+       assert(!ip_active(base) ||
+              (base->ip_receiver_name != MACH_PORT_NULL) ||
+              (base->ip_destination == IP_NULL));
+
+       /*
+        * Find the task to boost (if any).
+        * We will boost "through" ports that don't know
+        * about inheritance to deliver receive rights that
+        * do.
+        */
+       if (ip_active(base) && (assertcnt > 0)) {
+               assert(imp_lock_held);
+               if (base->ip_tempowner != 0) {
+                       if (IIT_NULL != base->ip_imp_task) {
+                               /* specified tempowner task */
+                               imp_task = base->ip_imp_task;
+                               assert(ipc_importance_task_is_any_receiver_type(imp_task));
+                       }
+                       /* otherwise don't boost current task */
+
+               } else if (base->ip_receiver_name != MACH_PORT_NULL) {
+                       ipc_space_t space = base->ip_receiver;
+
+                       /* only spaces with boost-accepting tasks */
+                       if (space->is_task != TASK_NULL &&
+                           ipc_importance_task_is_any_receiver_type(space->is_task->task_imp_base))
+                               imp_task = space->is_task->task_imp_base;
+               }
+
+               /* take reference before unlocking base */
+               if (imp_task != IIT_NULL) {
+                       ipc_importance_task_reference(imp_task);
+               }
+       }
+
+       if (update_knote) {
+               KNOTE(&base->ip_messages.imq_klist, 0);
+       }
+       imq_unlock(&base->ip_messages);
+       ip_unlock(base);
+
+       /*
+        * Transfer assertions now that the ports are unlocked.
+        * Avoid extra overhead if transferring to/from the same task.
+        *
+        * NOTE: If a transfer is occurring, the new assertions will
+        * be added to imp_task BEFORE the importance lock is unlocked.
+        * This is critical - to avoid decrements coming from the kmsgs
+        * beating the increment to the task.
+        */
+       boolean_t transfer_assertions = (imp_task != release_imp_task);
+
+       if (imp_task != IIT_NULL) {
+               assert(imp_lock_held);
+               if (transfer_assertions)
+                       ipc_importance_task_hold_internal_assertion_locked(imp_task, assertcnt);
+       }
+
+       if (release_imp_task != IIT_NULL) {
+               assert(imp_lock_held);
+               if (transfer_assertions)
+                       ipc_importance_task_drop_internal_assertion_locked(release_imp_task, assertcnt);
+       }
+
+       if (imp_lock_held)
+               ipc_importance_unlock();
+
+       if (imp_task != IIT_NULL)
+               ipc_importance_task_release(imp_task);
+
+       if (release_imp_task != IIT_NULL)
+               ipc_importance_task_release(release_imp_task);
+
+       return FALSE;
+}
+
 /*
  *     Routine:        ipc_importance_send
  *     Purpose:
@@ -2055,7 +2488,6 @@ ipc_importance_send(
        ipc_importance_task_t task_imp;
        kern_return_t kr;
 
-
        assert(IP_VALID(port));
 
        /* If no donation to be made, return quickly */
@@ -2068,7 +2500,12 @@ ipc_importance_send(
 
        /* If forced sending a static boost, go update the port */
        if ((option & MACH_SEND_IMPORTANCE) != 0) {
-               kmsg->ikm_header->msgh_bits |= MACH_MSGH_BITS_RAISEIMP;
+               /* acquire the importance lock while trying to hang on to port lock */
+               if (!ipc_importance_lock_try()) {
+                       port_lock_dropped = TRUE;
+                       ip_unlock(port);
+                       ipc_importance_lock();
+               }
                goto portupdate;
        }
 
@@ -2151,43 +2588,74 @@ ipc_importance_send(
                return port_lock_dropped;
        }
 
+portupdate:
        /* Mark the fact that we are (currently) donating through this message */
        kmsg->ikm_header->msgh_bits |= MACH_MSGH_BITS_RAISEIMP;
 
        /*
         * If we need to relock the port, do it with the importance still locked.
         * This assures we get to add the importance boost through the port to
-        * the task BEFORE anyone else can attempt to undo that operation because
+        * the task BEFORE anyone else can attempt to undo that operation if
         * the sender lost donor status.
         */
        if (TRUE == port_lock_dropped) {
                ip_lock(port);
        }
-       ipc_importance_unlock();
 
- portupdate:
-                               
-#if IMPORTANCE_DEBUG
+       ipc_importance_assert_held();
+
+#if IMPORTANCE_TRACE
        if (kdebug_enable) {
                mach_msg_max_trailer_t *dbgtrailer = (mach_msg_max_trailer_t *)
                                ((vm_offset_t)kmsg->ikm_header + round_msg(kmsg->ikm_header->msgh_size));
                unsigned int sender_pid = dbgtrailer->msgh_audit.val[5];
                mach_msg_id_t imp_msgh_id = kmsg->ikm_header->msgh_id;
                KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (IMPORTANCE_CODE(IMP_MSG, IMP_MSG_SEND)) | DBG_FUNC_START,
-                                          audit_token_pid_from_task(task), sender_pid, imp_msgh_id, 0, 0);
+                                          task_pid(task), sender_pid, imp_msgh_id, 0, 0);
        }
-#endif /* IMPORTANCE_DEBUG */
+#endif /* IMPORTANCE_TRACE */
+
+       mach_port_delta_t delta = 1;
+       boolean_t need_port_lock;
+       task_imp = IIT_NULL;
 
-       /* adjust port boost count (with port locked) */
-       if (TRUE == ipc_port_importance_delta(port, 1)) {
+       /* adjust port boost count (with importance and port locked) */
+       need_port_lock = ipc_port_importance_delta_internal(port, IPID_OPTION_NORMAL, &delta, &task_imp);
+       /* hold a reference on task_imp */
+
+       /* if we need to adjust a task importance as a result, apply that here */
+       if (IIT_NULL != task_imp && delta != 0) {
+               assert(delta == 1);
+
+               /* if this results in a change of state, propagate the transistion */
+               if (ipc_importance_task_check_transition(task_imp, IIT_UPDATE_HOLD, delta)) {
+
+                       /* can't hold the port lock during task transition(s) */
+                       if (!need_port_lock) {
+                               need_port_lock = TRUE;
+                               ip_unlock(port);
+                       }
+                       ipc_importance_task_propagate_assertion_locked(task_imp, IIT_UPDATE_HOLD, TRUE);
+               }
+       }
+
+       if (task_imp) {
+               ipc_importance_task_release_locked(task_imp);
+               /* importance unlocked */
+       } else {
+               ipc_importance_unlock();
+       }
+
+       if (need_port_lock) {
                port_lock_dropped = TRUE;
                ip_lock(port);
        }
+
        return port_lock_dropped;
 }
        
 /*
- *     Routine:        ipc_importance_inherit_from
+ *     Routine:        ipc_importance_inherit_from_kmsg
  *     Purpose:
  *             Create a "made" reference for an importance attribute representing
  *             an inheritance between the sender of a message (if linked) and the
@@ -2201,7 +2669,7 @@ ipc_importance_send(
  *             Nothing locked on entry.  May block.
  */
 static ipc_importance_inherit_t
-ipc_importance_inherit_from(ipc_kmsg_t kmsg)
+ipc_importance_inherit_from_kmsg(ipc_kmsg_t kmsg)
 {
        ipc_importance_task_t   task_imp = IIT_NULL;
        ipc_importance_elem_t   from_elem = kmsg->ikm_importance;
@@ -2211,7 +2679,6 @@ ipc_importance_inherit_from(ipc_kmsg_t kmsg)
        ipc_port_t port = kmsg->ikm_header->msgh_remote_port;
        ipc_importance_inherit_t inherit = III_NULL;
        ipc_importance_inherit_t alloc = III_NULL;
-       ipc_importance_inherit_t temp_inherit;
        boolean_t cleared_self_donation = FALSE;
        boolean_t donating;
        uint32_t depth = 1;
@@ -2309,14 +2776,7 @@ ipc_importance_inherit_from(ipc_kmsg_t kmsg)
         * check to see if we already have an inherit for this pairing
         */
        while (III_NULL == inherit) {
-               queue_iterate(&from_elem->iie_inherits, temp_inherit,
-                             ipc_importance_inherit_t, iii_inheritance) {
-                       if (temp_inherit->iii_to_task == task_imp &&
-                           temp_inherit->iii_depth == depth) {
-                               inherit = temp_inherit;
-                               break;
-                       }
-               }
+               inherit = ipc_importance_inherit_find(from_elem, task_imp, depth);
 
                /* Do we have to allocate a new inherit */
                if (III_NULL == inherit) {
@@ -2361,9 +2821,6 @@ ipc_importance_inherit_from(ipc_kmsg_t kmsg)
 
                /* add in a external reference for this use of the inherit */
                inherit->iii_externcnt++;
-               if (donating) {
-                       task_imp->iit_externcnt++;
-               }
        } else {
                /* initialize the previously allocated space */
                inherit = alloc;
@@ -2375,12 +2832,9 @@ ipc_importance_inherit_from(ipc_kmsg_t kmsg)
                inherit->iii_to_task = task_imp;
                inherit->iii_from_elem = IIE_NULL;
                queue_init(&inherit->iii_kmsgs);
-               queue_init(&inherit->iii_inherits);
 
-               /* If donating, reflect that in the task externcnt */
                if (donating) {
                        inherit->iii_donating = TRUE;
-                       task_imp->iit_externcnt++;
                } else {
                        inherit->iii_donating = FALSE;
                }
@@ -2409,6 +2863,14 @@ ipc_importance_inherit_from(ipc_kmsg_t kmsg)
        elem = ipc_importance_kmsg_unlink(kmsg);
        assert(elem == from_elem);
 
+       /* If found inherit and donating, reflect that in the task externcnt */
+       if (III_NULL != inherit && donating) {
+               task_imp->iit_externcnt++;
+               /* The owner of receive right might have changed, take the internal assertion */
+               ipc_importance_task_hold_internal_assertion_locked(task_imp, 1);
+               /* may have dropped and retaken importance lock */
+       }
+
        /* If we didn't create a new inherit, we have some resources to release */
        if (III_NULL == inherit || inherit != alloc) {
                if (IIE_NULL != from_elem) {
@@ -2437,23 +2899,16 @@ ipc_importance_inherit_from(ipc_kmsg_t kmsg)
                ipc_importance_unlock();
        }
 
-       /* decrement port boost count */ 
-       if (donating) {
-               ip_lock(port);
-               if (III_NULL != inherit) {
-                       /* task assertions transferred to inherit, just adjust port count */
-                       ipc_port_impcount_delta(port, -1, IP_NULL);
-                       ip_unlock(port);
-               }  else {
-                       /* drop importance from port and destination task */
-                       if (ipc_port_importance_delta(port, -1) == FALSE) {
-                               ip_unlock(port);
-                       }
-               }
-       } else if (cleared_self_donation) {
+       /*
+        * decrement port boost count
+        * This is OK to do without the importance lock as we atomically
+        * unlinked the kmsg and snapshot the donating state while holding
+        * the importance lock
+        */ 
+       if (donating || cleared_self_donation) {
                ip_lock(port);
-               /* drop cleared donation from port and destination task */
-               if (ipc_port_importance_delta(port, -1) == FALSE) {
+               /* drop importance from port and destination task */
+               if (ipc_port_importance_delta(port, IPID_OPTION_NORMAL, -1) == FALSE) {
                        ip_unlock(port);
                }
        }
@@ -2469,6 +2924,181 @@ ipc_importance_inherit_from(ipc_kmsg_t kmsg)
        return inherit;
 }
 
+/*
+ *     Routine:        ipc_importance_inherit_from_task
+ *     Purpose:
+ *             Create a reference for an importance attribute representing
+ *             an inheritance between the to_task and from_task. The iii
+ *             created will be marked as III_FLAGS_FOR_OTHERS.
+ *
+ *             It will not dedup any iii which are not marked as III_FLAGS_FOR_OTHERS.
+ *
+ *             If the task is inactive, there isn't any need to return a new reference.
+ *     Conditions:
+ *             Nothing locked on entry.  May block.
+ *             It should not be called from voucher subsystem.
+ */
+static ipc_importance_inherit_t
+ipc_importance_inherit_from_task(
+       task_t from_task,
+       task_t to_task)
+{
+       ipc_importance_task_t   to_task_imp = IIT_NULL;
+       ipc_importance_task_t   from_task_imp = IIT_NULL;
+       ipc_importance_elem_t   from_elem = IIE_NULL;
+
+       ipc_importance_inherit_t inherit = III_NULL;
+       ipc_importance_inherit_t alloc = III_NULL;
+       boolean_t donating;
+       uint32_t depth = 1;
+
+       to_task_imp = ipc_importance_for_task(to_task, FALSE);
+       from_task_imp = ipc_importance_for_task(from_task, FALSE);
+       from_elem = (ipc_importance_elem_t)from_task_imp;
+
+       ipc_importance_lock();
+
+       if (IIT_NULL == to_task_imp || IIT_NULL == from_task_imp) {
+               goto out_locked;
+       }
+
+       /*
+        * No need to set up an inherit linkage if the to_task or from_task
+        * isn't a receiver of one type or the other.
+        */
+       if (!ipc_importance_task_is_any_receiver_type(to_task_imp) ||
+           !ipc_importance_task_is_any_receiver_type(from_task_imp)) {
+               goto out_locked;
+       }
+
+       /* Do not allow to create a linkage to self */
+       if (to_task_imp == from_task_imp) {
+               goto out_locked;
+       }
+
+       incr_ref_counter(to_task_imp->iit_elem.iie_task_refs_added_inherit_from);
+       incr_ref_counter(from_elem->iie_kmsg_refs_added);
+
+       /*
+        * Now that we have the from_elem figured out,
+        * check to see if we already have an inherit for this pairing
+        */
+       while (III_NULL == inherit) {
+               inherit = ipc_importance_inherit_find(from_elem, to_task_imp, depth);
+
+               /* Do we have to allocate a new inherit */
+               if (III_NULL == inherit) {
+                       if (III_NULL != alloc) {
+                               break;
+                       }
+
+                       /* allocate space */
+                       ipc_importance_unlock();
+                       alloc = (ipc_importance_inherit_t)
+                               zalloc(ipc_importance_inherit_zone);
+                       ipc_importance_lock();
+               }
+       }
+
+       /* snapshot the donating status while we have importance locked */
+       donating = ipc_importance_task_is_donor(from_task_imp);
+
+       if (III_NULL != inherit) {
+               /* We found one, piggyback on that */
+               assert(0 < III_REFS(inherit));
+               assert(0 < IIE_REFS(inherit->iii_from_elem));
+
+               /* Take a reference for inherit */
+               assert(III_REFS_MAX > III_REFS(inherit));
+               ipc_importance_inherit_reference_internal(inherit);
+
+               /* Reflect the inherit's change of status into the task boosts */
+               if (0 == III_EXTERN(inherit)) {
+                       assert(!inherit->iii_donating);
+                       inherit->iii_donating = donating;
+                       if (donating) {
+                               to_task_imp->iit_externcnt += inherit->iii_externcnt;
+                               to_task_imp->iit_externdrop += inherit->iii_externdrop;
+                       }
+               } else {
+                       assert(donating == inherit->iii_donating);
+               }
+
+               /* add in a external reference for this use of the inherit */
+               inherit->iii_externcnt++;
+       } else {
+               /* initialize the previously allocated space */
+               inherit = alloc;
+               inherit->iii_bits = IIE_TYPE_INHERIT | 1;
+               inherit->iii_made = 0;
+               inherit->iii_externcnt = 1;
+               inherit->iii_externdrop = 0;
+               inherit->iii_depth = depth;
+               inherit->iii_to_task = to_task_imp;
+               inherit->iii_from_elem = IIE_NULL;
+               queue_init(&inherit->iii_kmsgs);
+
+               if (donating) {
+                       inherit->iii_donating = TRUE;
+               } else {
+                       inherit->iii_donating = FALSE;
+               }
+
+               /*
+                * Chain our new inherit on the element it inherits from.
+                * The new inherit takes our reference on from_elem.
+                */
+               ipc_importance_inherit_link(inherit, from_elem);
+
+#if IIE_REF_DEBUG
+               ipc_importance_counter_init(&inherit->iii_elem);
+               from_elem->iie_kmsg_refs_inherited++;
+               task_imp->iit_elem.iie_task_refs_inherited++;
+#endif
+       }
+
+out_locked:
+
+       /* If found inherit and donating, reflect that in the task externcnt */
+       if (III_NULL != inherit && donating) {
+               to_task_imp->iit_externcnt++;
+               /* take the internal assertion */
+               ipc_importance_task_hold_internal_assertion_locked(to_task_imp, 1);
+               /* may have dropped and retaken importance lock */
+       }
+
+       /* If we didn't create a new inherit, we have some resources to release */
+       if (III_NULL == inherit || inherit != alloc) {
+               if (IIE_NULL != from_elem) {
+                       if (III_NULL != inherit) {
+                               incr_ref_counter(from_elem->iie_kmsg_refs_coalesced);
+                       } else {
+                               incr_ref_counter(from_elem->iie_kmsg_refs_dropped);
+                       }
+                       ipc_importance_release_locked(from_elem);
+                       /* importance unlocked */
+               } else {
+                       ipc_importance_unlock();
+               }
+
+               if (IIT_NULL != to_task_imp) {
+                       if (III_NULL != inherit) {
+                               incr_ref_counter(to_task_imp->iit_elem.iie_task_refs_coalesced);
+                       }
+                       ipc_importance_task_release(to_task_imp);
+               }
+
+               if (III_NULL != alloc) {
+                       zfree(ipc_importance_inherit_zone, alloc);
+               }
+       } else {
+               /* from_elem and to_task_imp references transferred to new inherit */
+               ipc_importance_unlock();
+       }
+
+       return inherit;
+}
+
 /*
  *     Routine:        ipc_importance_receive
  *     Purpose:
@@ -2521,34 +3151,41 @@ ipc_importance_receive(
                 * transferring any boosts from the kmsg linkage through the
                 * port directly to the new inheritance object.
                 */
-               inherit = ipc_importance_inherit_from(kmsg);
+               inherit = ipc_importance_inherit_from_kmsg(kmsg);
                handle = (mach_voucher_attr_value_handle_t)inherit;
 
                assert(IIE_NULL == kmsg->ikm_importance);
 
-               /* replace the importance attribute with the handle we created */
-               /*  our made reference on the inhert is donated to the voucher */
-               recipe = (ipc_voucher_attr_recipe_t)&recipes[recipe_size];
-               recipe->key = MACH_VOUCHER_ATTR_KEY_IMPORTANCE;
-               recipe->command = MACH_VOUCHER_ATTR_SET_VALUE_HANDLE;
-               recipe->previous_voucher = IPC_VOUCHER_NULL;
-               recipe->content_size = sizeof(mach_voucher_attr_value_handle_t);
-               *(mach_voucher_attr_value_handle_t *)(void *)recipe->content = handle;
-               recipe_size += sizeof(*recipe) + sizeof(mach_voucher_attr_value_handle_t);
-
-               kr = ipc_voucher_attr_control_create_mach_voucher(ipc_importance_control,
-                                                                 recipes,
-                                                                 recipe_size,
-                                                                 &recv_voucher);
-               assert(KERN_SUCCESS == kr);
-
-               /* swap the voucher port (and set voucher bits in case it didn't already exist) */
-               kmsg->ikm_header->msgh_bits |= (MACH_MSG_TYPE_MOVE_SEND << 16);
-               ipc_port_release_send(kmsg->ikm_voucher);
-               kmsg->ikm_voucher = convert_voucher_to_port(recv_voucher);
-               if (III_NULL != inherit)
-                       impresult = 2;
-
+               /*
+                * Only create a new voucher if we have an inherit object
+                * (from the ikm_importance field of the incoming message), OR
+                * we have a valid incoming voucher. If we have neither of
+                * these things then there is no need to create a new voucher.
+                */
+               if (IP_VALID(kmsg->ikm_voucher) || inherit != III_NULL) {
+                       /* replace the importance attribute with the handle we created */
+                       /*  our made reference on the inherit is donated to the voucher */
+                       recipe = (ipc_voucher_attr_recipe_t)&recipes[recipe_size];
+                       recipe->key = MACH_VOUCHER_ATTR_KEY_IMPORTANCE;
+                       recipe->command = MACH_VOUCHER_ATTR_SET_VALUE_HANDLE;
+                       recipe->previous_voucher = IPC_VOUCHER_NULL;
+                       recipe->content_size = sizeof(mach_voucher_attr_value_handle_t);
+                       *(mach_voucher_attr_value_handle_t *)(void *)recipe->content = handle;
+                       recipe_size += sizeof(*recipe) + sizeof(mach_voucher_attr_value_handle_t);
+
+                       kr = ipc_voucher_attr_control_create_mach_voucher(ipc_importance_control,
+                                                                         recipes,
+                                                                         recipe_size,
+                                                                         &recv_voucher);
+                       assert(KERN_SUCCESS == kr);
+
+                       /* swap the voucher port (and set voucher bits in case it didn't already exist) */
+                       kmsg->ikm_header->msgh_bits |= (MACH_MSG_TYPE_MOVE_SEND << 16);
+                       ipc_port_release_send(kmsg->ikm_voucher);
+                       kmsg->ikm_voucher = convert_voucher_to_port(recv_voucher);
+                       if (III_NULL != inherit)
+                               impresult = 2;
+               }
        } else { /* Don't want a voucher */
 
                /* got linked importance? have to drop */
@@ -2569,26 +3206,28 @@ ipc_importance_receive(
                        ipc_importance_task_t task_imp = task_self->task_imp_base;
                        ipc_port_t port = kmsg->ikm_header->msgh_remote_port;
 
-                       /* defensive deduction for release builds lacking the assert */
-                       ip_lock(port);
-                       ipc_port_impcount_delta(port, -1, IP_NULL);
-                       ip_unlock(port);
-
-                       /* will user accept legacy responsibility for the importance boost */
-                       if (KERN_SUCCESS == ipc_importance_task_externalize_legacy_assertion(task_imp, 1, sender_pid)) {
+                       /* The owner of receive right might have changed, take the internal assertion */
+                       if (KERN_SUCCESS == ipc_importance_task_hold_internal_assertion(task_imp, 1)) {
+                               ipc_importance_task_externalize_legacy_assertion(task_imp, 1, sender_pid);
                                impresult = 1;
                        } else {
                                /* The importance boost never applied to task (clear the bit) */
                                kmsg->ikm_header->msgh_bits &= ~MACH_MSGH_BITS_RAISEIMP;
                                impresult = 0;
                        }
+
+                       /* Drop the boost on the port and the owner of the receive right */
+                       ip_lock(port);
+                       if (ipc_port_importance_delta(port, IPID_OPTION_NORMAL, -1) == FALSE) {
+                               ip_unlock(port);
+                       }
                }
        }
 
-#if IMPORTANCE_DEBUG
+#if IMPORTANCE_TRACE
        if (-1 < impresult)
                KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (IMPORTANCE_CODE(IMP_MSG, IMP_MSG_DELV)) | DBG_FUNC_NONE,
-                               sender_pid, audit_token_pid_from_task(task_self),
+                               sender_pid, task_pid(task_self),
                                kmsg->ikm_header->msgh_id, impresult, 0);
        if (impresult == 2){
                /*
@@ -2596,9 +3235,9 @@ ipc_importance_receive(
                 * will trigger the probe in ipc_importance_task_externalize_assertion() 
                 * above and have impresult==1 here.
                 */
-               DTRACE_BOOST5(receive_boost, task_t, task_self, int, audit_token_pid_from_task(task_self), int, sender_pid, int, 1, int, task_self->task_imp_base->iit_assertcnt);
+               DTRACE_BOOST5(receive_boost, task_t, task_self, int, task_pid(task_self), int, sender_pid, int, 1, int, task_self->task_imp_base->iit_assertcnt);
     }
-#endif /* IMPORTANCE_DEBUG */
+#endif /* IMPORTANCE_TRACE */
 }
 
 /*
@@ -2669,7 +3308,7 @@ ipc_importance_clean(
                        ip_lock(port);
                        /* inactive ports already had their importance boosts dropped */
                        if (!ip_active(port) || 
-                           ipc_port_importance_delta(port, -1) == FALSE) {
+                           ipc_port_importance_delta(port, IPID_OPTION_NORMAL, -1) == FALSE) {
                                ip_unlock(port);
                        }
                }
@@ -2704,6 +3343,7 @@ ipc_importance_get_value(
        mach_voucher_attr_content_t                     content,
        mach_voucher_attr_content_size_t                content_size,
        mach_voucher_attr_value_handle_t                *out_value,
+       mach_voucher_attr_value_flags_t                 *out_flags,
        ipc_voucher_t                                   *out_value_voucher);
 
 static kern_return_t
@@ -2738,6 +3378,7 @@ struct ipc_voucher_attr_manager ipc_importance_manager = {
        .ivam_extract_content = ipc_importance_extract_content,
        .ivam_command =         ipc_importance_command,
        .ivam_release =         ipc_importance_manager_release,
+       .ivam_flags =           IVAM_FLAGS_NONE,
 };
 
 #define IMPORTANCE_ASSERT_KEY(key) assert(MACH_VOUCHER_ATTR_KEY_IMPORTANCE == (key))
@@ -2780,9 +3421,9 @@ ipc_importance_release_value(
        /* clear made */ 
        elem->iie_made = 0;
 
-       /* 
-        * If there are pending external boosts represented by this attribute, 
-        * drop them from the apropriate task 
+       /*
+        * If there are pending external boosts represented by this attribute,
+        * drop them from the apropriate task
         */
        if (IIE_TYPE_INHERIT == IIE_TYPE(elem)) {
                ipc_importance_inherit_t inherit = (ipc_importance_inherit_t)elem;
@@ -2810,7 +3451,7 @@ ipc_importance_release_value(
                        inherit->iii_externcnt = 0;
                        inherit->iii_externdrop = 0;
                }
-       } 
+       }
 
        /* drop the made reference on elem */
        ipc_importance_release_locked(elem);
@@ -2840,6 +3481,7 @@ ipc_importance_get_value(
        mach_voucher_attr_content_t                     __unused content,
        mach_voucher_attr_content_size_t                content_size,
        mach_voucher_attr_value_handle_t                *out_value,
+       mach_voucher_attr_value_flags_t                 *out_flags,
        ipc_voucher_t                                   *out_value_voucher)
 {
        ipc_importance_elem_t elem;
@@ -2851,6 +3493,7 @@ ipc_importance_get_value(
        if (0 != content_size)
                return KERN_INVALID_ARGUMENT;
 
+       *out_flags = MACH_VOUCHER_ATTR_VALUE_FLAGS_NONE;
        /* never an out voucher */
 
        switch (command) {
@@ -2939,22 +3582,22 @@ ipc_importance_extract_content(
                        ipc_importance_inherit_t inherit = III_NULL;
                        ipc_importance_task_t task_imp;
                        task_t task;
-                       int task_pid;
+                       int t_pid;
 
                        if (IIE_TYPE_TASK == IIE_TYPE(elem)) {
                                task_imp = (ipc_importance_task_t)elem;
                                task = task_imp->iit_task;
-                               task_pid = (TASK_NULL != task) ?
-                                          audit_token_pid_from_task(task) : -1;
-                               snprintf((char *)out_content + size, *in_out_content_size - size, "%d", task_pid);
+                               t_pid = (TASK_NULL != task) ?
+                                          task_pid(task) : -1;
+                               snprintf((char *)out_content + size, *in_out_content_size - size, "%d", t_pid);
                        } else {
                                inherit = (ipc_importance_inherit_t)elem;
                                task_imp = inherit->iii_to_task;
                                task = task_imp->iit_task;
-                               task_pid = (TASK_NULL != task) ?
-                                          audit_token_pid_from_task(task) : -1;
+                               t_pid = (TASK_NULL != task) ?
+                                          task_pid(task) : -1;
                                snprintf((char *)out_content + size, *in_out_content_size - size, 
-                                        "%d (%d of %d boosts) %s from pid ", task_pid,
+                                        "%d (%d of %d boosts) %s from pid ", t_pid,
                                         III_EXTERN(inherit), inherit->iii_externcnt, 
                                         (inherit->iii_donating) ? "donated" : "linked");
                        }
@@ -3037,15 +3680,21 @@ ipc_importance_command(
                return KERN_SUCCESS;
        }
 
+       to_task = inherit->iii_to_task;
+       assert(ipc_importance_task_is_any_receiver_type(to_task));
+
+       /* if not donating to a denap receiver, it was called incorrectly */
+       if (!ipc_importance_task_is_marked_denap_receiver(to_task)) {
+               ipc_importance_unlock();
+               return KERN_INVALID_TASK; /* keeps dispatch happy */
+       }
+
        /* Enough external references left to drop? */
        if (III_EXTERN(inherit) < refs) {
                ipc_importance_unlock();
                return KERN_FAILURE;
        }
 
-       to_task = inherit->iii_to_task;
-       assert(ipc_importance_task_is_any_receiver_type(to_task));
-
        /* re-base external and internal counters at the inherit and the to-task (if apropos) */
        if (inherit->iii_donating) {
                assert(IIT_EXTERN(to_task) >= III_EXTERN(inherit));
@@ -3185,9 +3834,9 @@ ipc_importance_thread_call_init(void)
  *             Will panic the system otherwise.
  */
 extern int
-task_importance_list_pids(task_t task, int flags, int *pid_list, unsigned int max_count)
+task_importance_list_pids(task_t task, int flags, char *pid_list, unsigned int max_count)
 {
-       if (lck_spin_is_acquired(&ipc_importance_lock_data) ||
+       if (kdp_lck_spin_is_acquired(&ipc_importance_lock_data) ||
              max_count < 1 ||
              task->task_imp_base == IIT_NULL ||
              pid_list == NULL ||
@@ -3200,12 +3849,13 @@ task_importance_list_pids(task_t task, int flags, int *pid_list, unsigned int ma
        ipc_kmsg_t temp_kmsg;
        ipc_importance_inherit_t temp_inherit;
        ipc_importance_elem_t elem;
-       int target_pid;
+       int target_pid = 0, previous_pid;
 
        queue_iterate(&task_imp->iit_inherits, temp_inherit, ipc_importance_inherit_t, iii_inheritance) {
                /* check space in buffer */
                if (pidcount >= max_count) 
                        break;
+               previous_pid = target_pid;
                target_pid = -1;
 
                if (temp_inherit->iii_donating) {
@@ -3215,20 +3865,24 @@ task_importance_list_pids(task_t task, int flags, int *pid_list, unsigned int ma
 #else
                        temp_task = temp_inherit->iii_to_task->iit_task;
                        if (temp_task != TASK_NULL) {
-                               target_pid = audit_token_pid_from_task(temp_task);
+                               target_pid = task_pid(temp_task);
                        }
 #endif
                }
 
-               if (target_pid != -1) {
-                       pid_list[pidcount++] = target_pid;
+               if (target_pid != -1 && previous_pid != target_pid) {
+                       memcpy(pid_list, &target_pid, sizeof(target_pid));
+                       pid_list += sizeof(target_pid);
+                       pidcount++;
                }
 
        }
 
+       target_pid = 0;
        queue_iterate(&task_imp->iit_kmsgs, temp_kmsg, ipc_kmsg_t, ikm_inheritance) {
                if (pidcount >= max_count)
                        break;
+               previous_pid = target_pid;
                target_pid = -1;
                elem = temp_kmsg->ikm_importance;
                temp_task = TASK_NULL;
@@ -3243,7 +3897,7 @@ task_importance_list_pids(task_t task, int flags, int *pid_list, unsigned int ma
 
                if (IIE_TYPE_TASK == IIE_TYPE(elem) && 
                        (((ipc_importance_task_t)elem)->iit_task != TASK_NULL)) {
-                       target_pid = audit_token_pid_from_task(((ipc_importance_task_t)elem)->iit_task);
+                       target_pid = task_pid(((ipc_importance_task_t)elem)->iit_task);
                } else {
                        temp_inherit = (ipc_importance_inherit_t)elem;
 #if DEVELOPMENT || DEBUG
@@ -3251,13 +3905,15 @@ task_importance_list_pids(task_t task, int flags, int *pid_list, unsigned int ma
 #else
                        temp_task = temp_inherit->iii_to_task->iit_task;
                        if (temp_task != TASK_NULL) {
-                               target_pid = audit_token_pid_from_task(temp_task);
+                               target_pid = task_pid(temp_task);
                        }
 #endif
                }
 
-               if (target_pid != -1) {
-                       pid_list[pidcount++] = target_pid;
+               if (target_pid != -1 && previous_pid != target_pid) {
+                       memcpy(pid_list, &target_pid, sizeof(target_pid));
+                       pid_list += sizeof(target_pid);
+                       pidcount++;
                }
        }