xnu-7195.81.3.tar.gz

[apple/xnu.git] / osfmk / kern / work_interval.c

diff --git a/osfmk/kern/work_interval.c b/osfmk/kern/work_interval.c
index 4c1d4cbdae9fb5dec3ccc31b8b9ee6f876bb46c6..dd574a0b7ed3a9ad0ec2b87821626be6797aa67d 100644 (file)
--- a/osfmk/kern/work_interval.c
+++ b/osfmk/kern/work_interval.c
@@ -39,12 +39,87 @@
 #include <kern/task.h>
 #include <kern/coalition.h>
 #include <kern/policy_internal.h>
 #include <kern/task.h>
 #include <kern/coalition.h>
 #include <kern/policy_internal.h>

+#include <kern/mpsc_queue.h>

 
 #include <mach/kern_return.h>
 #include <mach/notify.h>
 
 #include <mach/kern_return.h>
 #include <mach/notify.h>

+#include <os/refcnt.h>

 
 #include <stdatomic.h>
 
 
 #include <stdatomic.h>
 

+/*
+ * With the introduction of auto-join work intervals, it is possible
+ * to change the work interval (and related thread group) of a thread in a
+ * variety of contexts (thread termination, context switch, thread mode
+ * change etc.). In order to clearly specify the policy expectation and
+ * the locking behavior, all calls to thread_set_work_interval() pass
+ * in a set of flags.
+ */
+
+__options_decl(thread_work_interval_options_t, uint32_t, {
+       /* Change the work interval using the explicit join rules */
+       THREAD_WI_EXPLICIT_JOIN_POLICY = 0x1,
+       /* Change the work interval using the auto-join rules */
+       THREAD_WI_AUTO_JOIN_POLICY     = 0x2,
+       /* Caller already holds the thread lock */
+       THREAD_WI_THREAD_LOCK_HELD     = 0x4,
+       /* Caller does not hold the thread lock */
+       THREAD_WI_THREAD_LOCK_NEEDED   = 0x8,
+       /* Change the work interval from the context switch path (thread may not be running or on a runq) */
+       THREAD_WI_THREAD_CTX_SWITCH    = 0x10,
+});
+
+static kern_return_t thread_set_work_interval(thread_t, struct work_interval *, thread_work_interval_options_t);
+
+#if CONFIG_SCHED_AUTO_JOIN
+/* MPSC queue used to defer deallocate work intervals */
+static struct mpsc_daemon_queue work_interval_deallocate_queue;
+
+static void work_interval_deferred_release(struct work_interval *);
+
+/*
+ * Work Interval Auto-Join Status
+ *
+ * work_interval_auto_join_status_t represents the state of auto-join for a given work interval.
+ * It packs the following information:
+ * - A bit representing if a "finish" is deferred on the work interval
+ * - Count of number of threads auto-joined to the work interval
+ */
+#define WORK_INTERVAL_STATUS_DEFERRED_FINISH_MASK    ((uint32_t)(1 << 31))
+#define WORK_INTERVAL_STATUS_AUTO_JOIN_COUNT_MASK    ((uint32_t)(WORK_INTERVAL_STATUS_DEFERRED_FINISH_MASK - 1))
+#define WORK_INTERVAL_STATUS_AUTO_JOIN_COUNT_MAX     WORK_INTERVAL_STATUS_AUTO_JOIN_COUNT_MASK
+typedef uint32_t work_interval_auto_join_status_t;
+
+static inline bool __unused
+work_interval_status_deferred_finish(work_interval_auto_join_status_t status)
+{
+       return (status & WORK_INTERVAL_STATUS_DEFERRED_FINISH_MASK) ? true : false;
+}
+
+static inline uint32_t __unused
+work_interval_status_auto_join_count(work_interval_auto_join_status_t status)
+{
+       return (uint32_t)(status & WORK_INTERVAL_STATUS_AUTO_JOIN_COUNT_MASK);
+}
+
+/*
+ * struct work_interval_deferred_finish_state
+ *
+ * Contains the parameters of the finish operation which is being deferred.
+ */
+struct work_interval_deferred_finish_state {
+       uint64_t instance_id;
+       uint64_t start;
+       uint64_t deadline;
+       uint64_t complexity;
+};
+
+struct work_interval_auto_join_info {
+       struct work_interval_deferred_finish_state deferred_finish_state;
+       work_interval_auto_join_status_t _Atomic status;
+};
+#endif /* CONFIG_SCHED_AUTO_JOIN */
+

 /*
  * Work Interval structs
  *
 /*
  * Work Interval structs
  *


@@ -66,7 +141,7 @@
 
 struct work_interval {
        uint64_t wi_id;
 
 struct work_interval {
        uint64_t wi_id;

-       _Atomic uint32_t wi_ref_count;
+       struct os_refcnt wi_ref_count;

        uint32_t wi_create_flags;
 
        /* for debugging purposes only, does not hold a ref on port */
        uint32_t wi_create_flags;
 
        /* for debugging purposes only, does not hold a ref on port */


@@ -81,72 +156,321 @@ struct work_interval {
        uint32_t wi_creator_pid;
        int wi_creator_pidversion;
 
        uint32_t wi_creator_pid;
        int wi_creator_pidversion;
 

+#if CONFIG_THREAD_GROUPS
+       struct thread_group *wi_group;  /* holds +1 ref on group */
+#endif /* CONFIG_THREAD_GROUPS */
+
+#if CONFIG_SCHED_AUTO_JOIN
+       /* Information related to auto-join and deferred finish for work interval */
+       struct work_interval_auto_join_info wi_auto_join_info;
+
+       /*
+        * Since the deallocation of auto-join work intervals
+        * can happen in the scheduler when the last thread in
+        * the WI blocks and the thread lock is held, the deallocation
+        * might have to be done on a separate thread.
+        */
+       struct mpsc_queue_chain   wi_deallocate_link;
+#endif /* CONFIG_SCHED_AUTO_JOIN */

 };
 
 };
 

+#if CONFIG_SCHED_AUTO_JOIN
+
+/*
+ * work_interval_perform_deferred_finish()
+ *
+ * Perform a deferred finish for a work interval. The routine accepts the deferred_finish_state as an
+ * argument rather than looking at the work_interval since the deferred finish can race with another
+ * start-finish cycle. To address that, the caller ensures that it gets a consistent snapshot of the
+ * deferred state before calling this routine. This allows the racing start-finish cycle to overwrite
+ * the deferred state without issues.
+ */

 static inline void
 static inline void

-wi_retain(struct work_interval *work_interval)
+work_interval_perform_deferred_finish(__unused struct work_interval_deferred_finish_state *deferred_finish_state,
+    __unused struct work_interval *work_interval, __unused thread_t thread)

 {
 {

-       uint32_t old_count;
-       old_count = atomic_fetch_add_explicit(&work_interval->wi_ref_count,
-           1, memory_order_relaxed);
-       assert(old_count > 0);
+
+       KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_SCHED_WI_DEFERRED_FINISH),
+           thread_tid(thread), thread_group_get_id(work_interval->wi_group));

 }
 
 }
 

-static inline void
-wi_release(struct work_interval *work_interval)
+/*
+ * work_interval_auto_join_increment()
+ *
+ * Routine to increment auto-join counter when a new thread is auto-joined to
+ * the work interval.
+ */
+static void
+work_interval_auto_join_increment(struct work_interval *work_interval)

 {
 {

-       uint32_t old_count;
-       old_count = atomic_fetch_sub_explicit(&work_interval->wi_ref_count,
-           1, memory_order_relaxed);
-       assert(old_count > 0);
+       struct work_interval_auto_join_info *join_info = &work_interval->wi_auto_join_info;
+       __assert_only work_interval_auto_join_status_t old_status = os_atomic_add_orig(&join_info->status, 1, relaxed);
+       assert(work_interval_status_auto_join_count(old_status) < WORK_INTERVAL_STATUS_AUTO_JOIN_COUNT_MAX);
+}

 
 

-       if (old_count == 1) {
+/*
+ * work_interval_auto_join_decrement()
+ *
+ * Routine to decrement the auto-join counter when a thread unjoins the work interval (due to
+ * blocking or termination). If this was the last auto-joined thread in the work interval and
+ * there was a deferred finish, performs the finish operation for the work interval.
+ */
+static void
+work_interval_auto_join_decrement(struct work_interval *work_interval, thread_t thread)
+{
+       struct work_interval_auto_join_info *join_info = &work_interval->wi_auto_join_info;
+       work_interval_auto_join_status_t old_status, new_status;
+       struct work_interval_deferred_finish_state deferred_finish_state;
+       bool perform_finish;
+
+       /* Update the auto-join count for the work interval atomically */
+       os_atomic_rmw_loop(&join_info->status, old_status, new_status, acquire, {
+               perform_finish = false;
+               new_status = old_status;
+               assert(work_interval_status_auto_join_count(old_status) > 0);
+               new_status -= 1;
+               if (new_status == WORK_INTERVAL_STATUS_DEFERRED_FINISH_MASK) {
+                       /* No auto-joined threads remaining and finish is deferred */
+                       new_status = 0;
+                       perform_finish = true;
+                       /*
+                        * Its important to copy the deferred finish state here so that this works
+                        * when racing with another start-finish cycle.
+                        */
+                       deferred_finish_state = join_info->deferred_finish_state;
+               }
+       });

 
 

-               kfree(work_interval, sizeof(struct work_interval));
+       if (perform_finish == true) {
+               /*
+                * Since work_interval_perform_deferred_finish() calls down to
+                * the machine layer callout for finish which gets the thread
+                * group from the thread passed in here, it is important to
+                * make sure that the thread still has the work interval thread
+                * group here.
+                */
+               assert(thread->thread_group == work_interval->wi_group);
+               work_interval_perform_deferred_finish(&deferred_finish_state, work_interval, thread);

        }
 }
 
 /*
        }
 }
 
 /*

- * work_interval_port_alloc
+ * work_interval_auto_join_enabled()
+ *
+ * Helper routine to check if work interval has auto-join enabled.
+ */
+static inline bool
+work_interval_auto_join_enabled(struct work_interval *work_interval)
+{
+       return (work_interval->wi_create_flags & WORK_INTERVAL_FLAG_ENABLE_AUTO_JOIN) != 0;
+}
+
+/*
+ * work_interval_deferred_finish_enabled()
+ *
+ * Helper routine to check if work interval has deferred finish enabled.
+ */
+static inline bool __unused
+work_interval_deferred_finish_enabled(struct work_interval *work_interval)
+{
+       return (work_interval->wi_create_flags & WORK_INTERVAL_FLAG_ENABLE_DEFERRED_FINISH) != 0;
+}
+
+#endif /* CONFIG_SCHED_AUTO_JOIN */
+
+static inline void
+work_interval_retain(struct work_interval *work_interval)
+{
+       /*
+        * Even though wi_retain is called under a port lock, we have
+        * to use os_ref_retain instead of os_ref_retain_locked
+        * because wi_release is not synchronized. wi_release calls
+        * os_ref_release which is unsafe to pair with os_ref_retain_locked.
+        */
+       os_ref_retain(&work_interval->wi_ref_count);
+}
+
+static inline void
+work_interval_deallocate(struct work_interval *work_interval)
+{
+       KDBG_RELEASE(MACHDBG_CODE(DBG_MACH_WORKGROUP, WORKGROUP_INTERVAL_DESTROY),
+           work_interval->wi_id);
+#if CONFIG_THREAD_GROUPS
+       thread_group_release(work_interval->wi_group);
+       work_interval->wi_group = NULL;
+#endif /* CONFIG_THREAD_GROUPS */
+       kfree(work_interval, sizeof(struct work_interval));
+}
+
+/*
+ * work_interval_release()
+ *
+ * Routine to release a ref count on the work interval. If the refcount goes down
+ * to zero, the work interval needs to be de-allocated.

  *
  *

- * Description: Obtain a send right for the given work interval struct.
+ * For non auto-join work intervals, they are de-allocated in this context.

  *
  *

- * Parameters:  work_interval - A work_interval struct
- *              Consumes a +1 ref count on work_interval, now owned by the port.
+ * For auto-join work intervals, the de-allocation cannot be done from this context
+ * since that might need the kernel memory allocator lock. In that case, the
+ * deallocation is done via a thread-call based mpsc queue.
+ */
+static void
+work_interval_release(struct work_interval *work_interval, __unused thread_work_interval_options_t options)
+{
+       if (os_ref_release(&work_interval->wi_ref_count) == 0) {
+#if CONFIG_SCHED_AUTO_JOIN
+               if (options & THREAD_WI_THREAD_LOCK_HELD) {
+                       work_interval_deferred_release(work_interval);
+               } else {
+                       work_interval_deallocate(work_interval);
+               }
+#else /* CONFIG_SCHED_AUTO_JOIN */
+               work_interval_deallocate(work_interval);
+#endif /* CONFIG_SCHED_AUTO_JOIN */
+       }
+}
+
+#if CONFIG_SCHED_AUTO_JOIN
+
+/*
+ * work_interval_deferred_release()

  *
  *

- * Returns:     Port of type IKOT_WORK_INTERVAL with work_interval set as its kobject.
- *              Returned with a +1 send right and no-senders notification armed.
- *              Work interval struct reference is held by the port.
+ * Routine to enqueue the work interval on the deallocation mpsc queue.

  */
  */

-static ipc_port_t
-work_interval_port_alloc(struct work_interval *work_interval)
+static void
+work_interval_deferred_release(struct work_interval *work_interval)

 {
 {

-       ipc_port_t work_interval_port = ipc_port_alloc_kernel();
+       mpsc_daemon_enqueue(&work_interval_deallocate_queue,
+           &work_interval->wi_deallocate_link, MPSC_QUEUE_NONE);
+}

 
 

-       if (work_interval_port == IP_NULL) {
-               panic("failed to allocate work interval port");
+/*
+ * work_interval_should_propagate()
+ *
+ * Main policy routine to decide if a thread should be auto-joined to
+ * another thread's work interval. The conditions are arranged such that
+ * the most common bailout condition are checked the earliest. This routine
+ * is called from the scheduler context; so it needs to be efficient and
+ * be careful when taking locks or performing wakeups.
+ */
+inline bool
+work_interval_should_propagate(thread_t cthread, thread_t thread)
+{
+       /* Only allow propagation if the current thread has a work interval and the woken up thread does not */
+       if ((cthread->th_work_interval == NULL) || (thread->th_work_interval != NULL)) {
+               return false;

        }
 
        }
 

-       assert(work_interval->wi_port == IP_NULL);
+       /* Only propagate work intervals which have auto-join enabled */
+       if (work_interval_auto_join_enabled(cthread->th_work_interval) == false) {
+               return false;
+       }

 
 

-       ip_lock(work_interval_port);
-       ipc_kobject_set_atomically(work_interval_port, (ipc_kobject_t)work_interval,
-           IKOT_WORK_INTERVAL);
+       /* Work interval propagation is enabled for realtime threads only */
+       if ((cthread->sched_mode != TH_MODE_REALTIME) || (thread->sched_mode != TH_MODE_REALTIME)) {
+               return false;
+       }

 
 

-       ipc_port_t notify_port = ipc_port_make_sonce_locked(work_interval_port);
-       ipc_port_t old_notify_port = IP_NULL;
-       ipc_port_nsrequest(work_interval_port, 1, notify_port, &old_notify_port);
-       /* port unlocked */

 
 

-       assert(old_notify_port == IP_NULL);
+       /* Work interval propagation only works for threads with the same home thread group */
+       struct thread_group *thread_home_tg = thread_group_get_home_group(thread);
+       if (thread_group_get_home_group(cthread) != thread_home_tg) {
+               return false;
+       }

 
 

-       /* This is the only make-send that will happen on this port */
-       ipc_port_t send_port = ipc_port_make_send(work_interval_port);
-       assert(IP_VALID(send_port));
+       /* If woken up thread has adopted vouchers and other thread groups, it does not get propagation */
+       if (thread->thread_group != thread_home_tg) {
+               return false;
+       }

 
 

-       work_interval->wi_port = work_interval_port;
+       /* If either thread is inactive (in the termination path), do not propagate auto-join */
+       if ((!cthread->active) || (!thread->active)) {
+               return false;
+       }

 
 

-       return send_port;
+       return true;
+}
+
+/*
+ * work_interval_auto_join_propagate()
+ *
+ * Routine to auto-join a thread into another thread's work interval
+ *
+ * Should only be invoked if work_interval_should_propagate() returns
+ * true. Also expects "from" thread to be current thread and "to" thread
+ * to be locked.
+ */
+void
+work_interval_auto_join_propagate(thread_t from, thread_t to)
+{
+       assert(from == current_thread());
+       work_interval_retain(from->th_work_interval);
+       work_interval_auto_join_increment(from->th_work_interval);
+       __assert_only kern_return_t kr = thread_set_work_interval(to, from->th_work_interval,
+           THREAD_WI_AUTO_JOIN_POLICY | THREAD_WI_THREAD_LOCK_HELD | THREAD_WI_THREAD_CTX_SWITCH);
+       assert(kr == KERN_SUCCESS);
+}
+
+/*
+ * work_interval_auto_join_unwind()
+ *
+ * Routine to un-join an auto-joined work interval for a thread that is blocking.
+ *
+ * Expects thread to be locked.
+ */
+void
+work_interval_auto_join_unwind(thread_t thread)
+{
+       __assert_only kern_return_t kr = thread_set_work_interval(thread, NULL,
+           THREAD_WI_AUTO_JOIN_POLICY | THREAD_WI_THREAD_LOCK_HELD | THREAD_WI_THREAD_CTX_SWITCH);
+       assert(kr == KERN_SUCCESS);
+}
+
+/*
+ * work_interval_auto_join_demote()
+ *
+ * Routine to un-join an auto-joined work interval when a thread is changing from
+ * realtime to non-realtime scheduling mode. This could happen due to multiple
+ * reasons such as RT failsafe, thread backgrounding or thread termination. Also,
+ * the thread being demoted may not be the current thread.
+ *
+ * Expects thread to be locked.
+ */
+void
+work_interval_auto_join_demote(thread_t thread)
+{
+       __assert_only kern_return_t kr = thread_set_work_interval(thread, NULL,
+           THREAD_WI_AUTO_JOIN_POLICY | THREAD_WI_THREAD_LOCK_HELD);
+       assert(kr == KERN_SUCCESS);
+}
+
+static void
+work_interval_deallocate_queue_invoke(mpsc_queue_chain_t e,
+    __assert_only mpsc_daemon_queue_t dq)
+{
+       struct work_interval *work_interval = NULL;
+       work_interval = mpsc_queue_element(e, struct work_interval, wi_deallocate_link);
+       assert(dq == &work_interval_deallocate_queue);
+       assert(os_ref_get_count(&work_interval->wi_ref_count) == 0);
+       work_interval_deallocate(work_interval);
+}
+
+#endif /* CONFIG_SCHED_AUTO_JOIN */
+
+void
+work_interval_subsystem_init(void)
+{
+#if CONFIG_SCHED_AUTO_JOIN
+       /*
+        * The work interval deallocation queue must be a thread call based queue
+        * because it is woken up from contexts where the thread lock is held. The
+        * only way to perform wakeups safely in those contexts is to wakeup a
+        * thread call which is guaranteed to be on a different waitq and would
+        * not hash onto the same global waitq which might be currently locked.
+        */
+       mpsc_daemon_queue_init_with_thread_call(&work_interval_deallocate_queue,
+           work_interval_deallocate_queue_invoke, THREAD_CALL_PRIORITY_KERNEL);
+#endif /* CONFIG_SCHED_AUTO_JOIN */

 }
 
 /*
 }
 
 /*


@@ -172,9 +496,9 @@ work_interval_port_convert_locked(ipc_port_t port)
                return NULL;
        }
 
                return NULL;
        }
 

-       work_interval = (struct work_interval *)port->ip_kobject;
+       work_interval = (struct work_interval *) ip_get_kobject(port);

 
 

-       wi_retain(work_interval);
+       work_interval_retain(work_interval);

 
        return work_interval;
 }
 
        return work_interval;
 }


@@ -271,7 +595,7 @@ work_interval_port_notify(mach_msg_header_t *msg)
                    port, port->ip_srights);
        }
 
                    port, port->ip_srights);
        }
 

-       work_interval = (struct work_interval *)port->ip_kobject;
+       work_interval = (struct work_interval *) ip_get_kobject(port);

 
        if (work_interval == NULL) {
                panic("work_interval_port_notify(): missing kobject: %p", port);
 
        if (work_interval == NULL) {
                panic("work_interval_port_notify(): missing kobject: %p", port);


@@ -284,44 +608,189 @@ work_interval_port_notify(mach_msg_header_t *msg)
        ip_unlock(port);
 
        ipc_port_dealloc_kernel(port);
        ip_unlock(port);
 
        ipc_port_dealloc_kernel(port);

-       wi_release(work_interval);
+       work_interval_release(work_interval, THREAD_WI_THREAD_LOCK_NEEDED);

 }
 
 /*
 }
 
 /*

+ * work_interval_port_type()
+ *
+ * Converts a port name into the work interval object and returns its type.
+ *
+ * For invalid ports, it returns WORK_INTERVAL_TYPE_LAST (which is not a
+ * valid type for work intervals).
+ */
+static uint32_t
+work_interval_port_type(mach_port_name_t port_name)
+{
+       struct work_interval *work_interval = NULL;
+       kern_return_t kr;
+       uint32_t work_interval_type;
+
+       if (port_name == MACH_PORT_NULL) {
+               return WORK_INTERVAL_TYPE_LAST;
+       }
+
+       kr = port_name_to_work_interval(port_name, &work_interval);
+       if (kr != KERN_SUCCESS) {
+               return WORK_INTERVAL_TYPE_LAST;
+       }
+       /* work_interval has a +1 ref */
+
+       assert(work_interval != NULL);
+       work_interval_type = work_interval->wi_create_flags & WORK_INTERVAL_TYPE_MASK;
+       work_interval_release(work_interval, THREAD_WI_THREAD_LOCK_NEEDED);
+       return work_interval_type;
+}
+
+
+/*
+ * thread_set_work_interval()
+ *

  * Change thread's bound work interval to the passed-in work interval
  * Change thread's bound work interval to the passed-in work interval

- * Consumes +1 ref on work_interval
+ * Consumes +1 ref on work_interval upon success.

  *
  * May also pass NULL to un-set work_interval on the thread
  *
  * May also pass NULL to un-set work_interval on the thread

- *

  * Will deallocate any old work interval on the thread
  * Will deallocate any old work interval on the thread

+ * Return error if thread does not satisfy requirements to join work interval
+ *
+ * For non auto-join work intervals, deallocate any old work interval on the thread
+ * For auto-join work intervals, the routine may wakeup the work interval deferred
+ * deallocation queue since thread locks might be currently held.

  */
  */

-static void
+static kern_return_t

 thread_set_work_interval(thread_t thread,
 thread_set_work_interval(thread_t thread,

-    struct work_interval *work_interval)
+    struct work_interval *work_interval, thread_work_interval_options_t options)

 {
 {

-       assert(thread == current_thread());
+       /* All explicit work interval operations should always be from the current thread */
+       if (options & THREAD_WI_EXPLICIT_JOIN_POLICY) {
+               assert(thread == current_thread());
+       }
+
+       /* All cases of needing the thread lock should be from explicit join scenarios */
+       if (options & THREAD_WI_THREAD_LOCK_NEEDED) {
+               assert((options & THREAD_WI_EXPLICIT_JOIN_POLICY) != 0);
+       }
+
+       /* For all cases of auto join must come in with the thread lock held */
+       if (options & THREAD_WI_AUTO_JOIN_POLICY) {
+               assert((options & THREAD_WI_THREAD_LOCK_HELD) != 0);
+       }
+
+       if (work_interval) {
+               uint32_t work_interval_type = work_interval->wi_create_flags & WORK_INTERVAL_TYPE_MASK;
+
+               if ((work_interval_type == WORK_INTERVAL_TYPE_COREAUDIO) &&
+                   (thread->sched_mode != TH_MODE_REALTIME) && (thread->saved_mode != TH_MODE_REALTIME)) {
+                       return KERN_INVALID_ARGUMENT;
+               }
+       }

 
        struct work_interval *old_th_wi = thread->th_work_interval;
 
        struct work_interval *old_th_wi = thread->th_work_interval;

+#if CONFIG_SCHED_AUTO_JOIN
+       bool old_wi_auto_joined = ((thread->sched_flags & TH_SFLAG_THREAD_GROUP_AUTO_JOIN) != 0);
+
+       spl_t s;
+       /* Take the thread lock if needed */
+       if (options & THREAD_WI_THREAD_LOCK_NEEDED) {
+               s = splsched();
+               thread_lock(thread);
+       }
+
+       /*
+        * Work interval auto-join leak to non-RT threads.
+        *
+        * If thread might be running on a remote core and it's not in the context switch path (where
+        * thread is neither running, blocked or in the runq), its not possible to update the
+        * work interval & thread group remotely since its not possible to update CLPC for a remote
+        * core. This situation might happen when a thread is transitioning from realtime to
+        * non-realtime due to backgrounding etc., which would mean that non-RT threads would now
+        * be part of the work interval.
+        *
+        * Since there is no immediate mitigation to this issue, the policy is to set a new
+        * flag on the thread which indicates that such a "leak" has happened. This flag will
+        * be cleared when the remote thread eventually blocks and unjoins from the work interval.
+        */
+       bool thread_on_remote_core = ((thread != current_thread()) && (thread->state & TH_RUN) && (thread->runq == PROCESSOR_NULL));
+
+       if (thread_on_remote_core && ((options & THREAD_WI_THREAD_CTX_SWITCH) == 0)) {
+               assert((options & THREAD_WI_THREAD_LOCK_NEEDED) == 0);
+               os_atomic_or(&thread->th_work_interval_flags, TH_WORK_INTERVAL_FLAGS_AUTO_JOIN_LEAK, relaxed);
+               return KERN_SUCCESS;
+       }
+
+       old_wi_auto_joined = ((thread->sched_flags & TH_SFLAG_THREAD_GROUP_AUTO_JOIN) != 0);
+
+       if ((options & THREAD_WI_AUTO_JOIN_POLICY) || old_wi_auto_joined) {
+               __kdebug_only uint64_t old_tg_id = (old_th_wi) ? thread_group_get_id(old_th_wi->wi_group) : ~0;
+               __kdebug_only uint64_t new_tg_id = (work_interval) ? thread_group_get_id(work_interval->wi_group) : ~0;
+               KDBG(MACHDBG_CODE(DBG_MACH_SCHED, MACH_SCHED_WI_AUTO_JOIN),
+                   thread_tid(thread), old_tg_id, new_tg_id, options);
+       }
+
+       if (old_wi_auto_joined) {
+               /*
+                * If thread was auto-joined to a work interval and is not realtime, make sure it
+                * happened due to the "leak" described above.
+                */
+               if (thread->sched_mode != TH_MODE_REALTIME) {
+                       assert((thread->th_work_interval_flags & TH_WORK_INTERVAL_FLAGS_AUTO_JOIN_LEAK) != 0);
+               }
+
+               os_atomic_andnot(&thread->th_work_interval_flags, TH_WORK_INTERVAL_FLAGS_AUTO_JOIN_LEAK, relaxed);
+               work_interval_auto_join_decrement(old_th_wi, thread);
+               thread->sched_flags &= ~TH_SFLAG_THREAD_GROUP_AUTO_JOIN;
+       }
+
+#endif /* CONFIG_SCHED_AUTO_JOIN */
+
+       KDBG_RELEASE(MACHDBG_CODE(DBG_MACH_WORKGROUP, WORKGROUP_INTERVAL_CHANGE),
+           thread_tid(thread), (old_th_wi ? old_th_wi->wi_id : 0), (work_interval ? work_interval->wi_id : 0), !!(options & THREAD_WI_AUTO_JOIN_POLICY));

 
        /* transfer +1 ref to thread */
        thread->th_work_interval = work_interval;
 
 
        /* transfer +1 ref to thread */
        thread->th_work_interval = work_interval;
 

+#if CONFIG_SCHED_AUTO_JOIN
+
+       if ((options & THREAD_WI_AUTO_JOIN_POLICY) && work_interval) {
+               assert(work_interval_auto_join_enabled(work_interval) == true);
+               thread->sched_flags |= TH_SFLAG_THREAD_GROUP_AUTO_JOIN;
+       }
+
+       if (options & THREAD_WI_THREAD_LOCK_NEEDED) {
+               thread_unlock(thread);
+               splx(s);
+       }
+#endif /* CONFIG_SCHED_AUTO_JOIN */
+
+#if CONFIG_THREAD_GROUPS
+       struct thread_group *new_tg = (work_interval) ? (work_interval->wi_group) : NULL;
+       thread_set_work_interval_thread_group(thread, new_tg, (options & THREAD_WI_AUTO_JOIN_POLICY));
+#endif /* CONFIG_THREAD_GROUPS */

 
        if (old_th_wi != NULL) {
 
        if (old_th_wi != NULL) {

-               wi_release(old_th_wi);
+               work_interval_release(old_th_wi, options);

        }
        }

+
+       return KERN_SUCCESS;

 }
 
 }
 

-void
+static kern_return_t
+thread_set_work_interval_explicit_join(thread_t thread, struct work_interval *work_interval)
+{
+       assert(thread == current_thread());
+       return thread_set_work_interval(thread, work_interval, THREAD_WI_EXPLICIT_JOIN_POLICY | THREAD_WI_THREAD_LOCK_NEEDED);
+}
+
+kern_return_t

 work_interval_thread_terminate(thread_t thread)
 {
 work_interval_thread_terminate(thread_t thread)
 {

+       assert(thread == current_thread());

        if (thread->th_work_interval != NULL) {
        if (thread->th_work_interval != NULL) {

-               thread_set_work_interval(thread, NULL);
+               return thread_set_work_interval(thread, NULL, THREAD_WI_EXPLICIT_JOIN_POLICY | THREAD_WI_THREAD_LOCK_NEEDED);

        }
        }

+       return KERN_SUCCESS;

 }
 
 }
 

-
-

 kern_return_t
 kern_work_interval_notify(thread_t thread, struct kern_work_interval_args* kwi_args)
 {
 kern_return_t
 kern_work_interval_notify(thread_t thread, struct kern_work_interval_args* kwi_args)
 {


@@ -346,9 +815,12 @@ kern_work_interval_notify(thread_t thread, struct kern_work_interval_args* kwi_a
 
        spl_t s = splsched();
 
 
        spl_t s = splsched();
 

+#if CONFIG_THREAD_GROUPS
+       assert(work_interval->wi_group == thread->thread_group);
+#endif /* CONFIG_THREAD_GROUPS */

 
        uint64_t urgency_param1, urgency_param2;
 
        uint64_t urgency_param1, urgency_param2;

-       kwi_args->urgency = thread_get_urgency(thread, &urgency_param1, &urgency_param2);
+       kwi_args->urgency = (uint16_t)thread_get_urgency(thread, &urgency_param1, &urgency_param2);

 
        splx(s);
 
 
        splx(s);
 


@@ -367,61 +839,126 @@ kern_work_interval_create(thread_t thread,
 {
        assert(thread == current_thread());
 
 {
        assert(thread == current_thread());
 

-       if (thread->th_work_interval != NULL) {
-               /* already assigned a work interval */
-               return KERN_FAILURE;
-       }
-
-       struct work_interval *work_interval = kalloc(sizeof(*work_interval));
+       uint32_t create_flags = create_params->wica_create_flags;

 
 

-       if (work_interval == NULL) {
-               panic("failed to allocate work_interval");
+       if (((create_flags & WORK_INTERVAL_FLAG_JOINABLE) == 0) &&
+           thread->th_work_interval != NULL) {
+               /*
+                * If the thread is doing a legacy combined create and join,
+                * it shouldn't already be part of a work interval.
+                *
+                * (Creating a joinable WI is allowed anytime.)
+                */
+               return KERN_FAILURE;

        }
 
        }
 

-       bzero(work_interval, sizeof(*work_interval));
-
-       uint64_t old_value = atomic_fetch_add_explicit(&unique_work_interval_id, 1,
-           memory_order_relaxed);
-
-       uint64_t work_interval_id = old_value + 1;
-
-       uint32_t create_flags = create_params->wica_create_flags;
-
+       /*
+        * Check the validity of the create flags before allocating the work
+        * interval.
+        */

        task_t creating_task = current_task();
        if ((create_flags & WORK_INTERVAL_TYPE_MASK) == WORK_INTERVAL_TYPE_CA_CLIENT) {
                /*
        task_t creating_task = current_task();
        if ((create_flags & WORK_INTERVAL_TYPE_MASK) == WORK_INTERVAL_TYPE_CA_CLIENT) {
                /*

-                * CA_CLIENT work intervals do not create new thread groups
-                * and are non-joinable.
-                * There can only be one CA_CLIENT work interval (created by UIKit)
+                * CA_CLIENT work intervals do not create new thread groups.
+                * There can only be one CA_CLIENT work interval (created by UIKit or AppKit)

                 * per each application task
                 */
                 * per each application task
                 */

-               if (create_flags & (WORK_INTERVAL_FLAG_JOINABLE | WORK_INTERVAL_FLAG_GROUP)) {
+               if (create_flags & WORK_INTERVAL_FLAG_GROUP) {

                        return KERN_FAILURE;
                }
                if (!task_is_app(creating_task)) {
                        return KERN_FAILURE;
                }
                if (!task_is_app(creating_task)) {

+#if XNU_TARGET_OS_OSX
+                       /*
+                        * Soft-fail the case of a non-app pretending to be an
+                        * app, by allowing it to press the buttons, but they're
+                        * not actually connected to anything.
+                        */
+                       create_flags |= WORK_INTERVAL_FLAG_IGNORED;
+#else
+                       /*
+                        * On iOS, it's a hard failure to get your apptype
+                        * wrong and then try to render something.
+                        */

                        return KERN_NOT_SUPPORTED;
                        return KERN_NOT_SUPPORTED;

+#endif /* XNU_TARGET_OS_OSX */

                }
                if (task_set_ca_client_wi(creating_task, true) == false) {
                        return KERN_FAILURE;
                }
        }
 
                }
                if (task_set_ca_client_wi(creating_task, true) == false) {
                        return KERN_FAILURE;
                }
        }
 

+#if CONFIG_SCHED_AUTO_JOIN
+       if (create_flags & WORK_INTERVAL_FLAG_ENABLE_AUTO_JOIN) {
+               uint32_t type = (create_flags & WORK_INTERVAL_TYPE_MASK);
+               if (type != WORK_INTERVAL_TYPE_COREAUDIO) {
+                       return KERN_NOT_SUPPORTED;
+               }
+               if ((create_flags & WORK_INTERVAL_FLAG_GROUP) == 0) {
+                       return KERN_NOT_SUPPORTED;
+               }
+       }
+
+       if (create_flags & WORK_INTERVAL_FLAG_ENABLE_DEFERRED_FINISH) {
+               if ((create_flags & WORK_INTERVAL_FLAG_ENABLE_AUTO_JOIN) == 0) {
+                       return KERN_NOT_SUPPORTED;
+               }
+       }
+#endif /* CONFIG_SCHED_AUTO_JOIN */
+
+       struct work_interval *work_interval = kalloc_flags(sizeof(*work_interval),
+           Z_WAITOK | Z_ZERO);
+       assert(work_interval != NULL);
+
+       uint64_t work_interval_id = os_atomic_inc(&unique_work_interval_id, relaxed);
+

        *work_interval = (struct work_interval) {
                .wi_id                  = work_interval_id,
        *work_interval = (struct work_interval) {
                .wi_id                  = work_interval_id,

-               .wi_ref_count           = 1,
+               .wi_ref_count           = {},

                .wi_create_flags        = create_flags,
                .wi_creator_pid         = pid_from_task(creating_task),
                .wi_creator_uniqueid    = get_task_uniqueid(creating_task),
                .wi_creator_pidversion  = get_task_version(creating_task),
        };
                .wi_create_flags        = create_flags,
                .wi_creator_pid         = pid_from_task(creating_task),
                .wi_creator_uniqueid    = get_task_uniqueid(creating_task),
                .wi_creator_pidversion  = get_task_version(creating_task),
        };

+       os_ref_init(&work_interval->wi_ref_count, NULL);
+
+       __kdebug_only uint64_t tg_id = 0;
+#if CONFIG_THREAD_GROUPS
+       struct thread_group *tg;
+       if (create_flags & WORK_INTERVAL_FLAG_GROUP) {
+               /* create a new group for the interval to represent */
+               char name[THREAD_GROUP_MAXNAME] = "";
+
+               snprintf(name, sizeof(name), "WI[%d] #%lld",
+                   work_interval->wi_creator_pid, work_interval_id);
+
+               tg = thread_group_create_and_retain();
+
+               thread_group_set_name(tg, name);
+
+               work_interval->wi_group = tg;
+       } else {
+               /* the interval represents the thread's home group */
+               tg = thread_group_get_home_group(thread);
+
+               thread_group_retain(tg);
+
+               work_interval->wi_group = tg;
+       }
+
+       /* Capture the tg_id for tracing purposes */
+       tg_id = thread_group_get_id(work_interval->wi_group);

 
 

+#endif /* CONFIG_THREAD_GROUPS */

 
        if (create_flags & WORK_INTERVAL_FLAG_JOINABLE) {
 
        if (create_flags & WORK_INTERVAL_FLAG_JOINABLE) {

-               /* work_interval has a +1 ref, moves to the port */
-               ipc_port_t port = work_interval_port_alloc(work_interval);

                mach_port_name_t name = MACH_PORT_NULL;
 
                mach_port_name_t name = MACH_PORT_NULL;
 

-               name = ipc_port_copyout_send(port, current_space());
+               /* work_interval has a +1 ref, moves to the port */
+               work_interval->wi_port = ipc_kobject_alloc_port(
+                       (ipc_kobject_t)work_interval, IKOT_WORK_INTERVAL,
+                       IPC_KOBJECT_ALLOC_MAKE_SEND | IPC_KOBJECT_ALLOC_NSREQUEST);
+
+               name = ipc_port_copyout_send(work_interval->wi_port, current_space());

 
                if (!MACH_PORT_VALID(name)) {
                        /*
 
                if (!MACH_PORT_VALID(name)) {
                        /*


@@ -435,11 +972,41 @@ kern_work_interval_create(thread_t thread,
                create_params->wica_port = name;
        } else {
                /* work_interval has a +1 ref, moves to the thread */
                create_params->wica_port = name;
        } else {
                /* work_interval has a +1 ref, moves to the thread */

-               thread_set_work_interval(thread, work_interval);
+               kern_return_t kr = thread_set_work_interval_explicit_join(thread, work_interval);
+               if (kr != KERN_SUCCESS) {
+                       /* No other thread can join this work interval since it isn't
+                        * JOINABLE so release the reference on work interval */
+                       work_interval_release(work_interval, THREAD_WI_THREAD_LOCK_NEEDED);
+                       return kr;
+               }

                create_params->wica_port = MACH_PORT_NULL;
        }
 
        create_params->wica_id = work_interval_id;
                create_params->wica_port = MACH_PORT_NULL;
        }
 
        create_params->wica_id = work_interval_id;

+
+       KDBG_RELEASE(MACHDBG_CODE(DBG_MACH_WORKGROUP, WORKGROUP_INTERVAL_CREATE),
+           work_interval_id, create_flags, pid_from_task(creating_task), tg_id);
+       return KERN_SUCCESS;
+}
+
+kern_return_t
+kern_work_interval_get_flags_from_port(mach_port_name_t port_name, uint32_t *flags)
+{
+       assert(flags != NULL);
+
+       kern_return_t kr;
+       struct work_interval *work_interval;
+
+       kr = port_name_to_work_interval(port_name, &work_interval);
+       if (kr != KERN_SUCCESS) {
+               return kr;
+       }
+
+       assert(work_interval != NULL);
+       *flags = work_interval->wi_create_flags;
+
+       work_interval_release(work_interval, THREAD_WI_THREAD_LOCK_NEEDED);
+

        return KERN_SUCCESS;
 }
 
        return KERN_SUCCESS;
 }
 


@@ -457,9 +1024,7 @@ kern_work_interval_destroy(thread_t thread, uint64_t work_interval_id)
                return KERN_INVALID_ARGUMENT;
        }
 
                return KERN_INVALID_ARGUMENT;
        }
 

-       thread_set_work_interval(thread, NULL);
-
-       return KERN_SUCCESS;
+       return thread_set_work_interval_explicit_join(thread, NULL);

 }
 
 kern_return_t
 }
 
 kern_return_t


@@ -471,8 +1036,7 @@ kern_work_interval_join(thread_t            thread,
 
        if (port_name == MACH_PORT_NULL) {
                /* 'Un-join' the current work interval */
 
        if (port_name == MACH_PORT_NULL) {
                /* 'Un-join' the current work interval */

-               thread_set_work_interval(thread, NULL);
-               return KERN_SUCCESS;
+               return thread_set_work_interval_explicit_join(thread, NULL);

        }
 
        kr = port_name_to_work_interval(port_name, &work_interval);
        }
 
        kr = port_name_to_work_interval(port_name, &work_interval);


@@ -483,9 +1047,22 @@ kern_work_interval_join(thread_t            thread,
 
        assert(work_interval != NULL);
 
 
        assert(work_interval != NULL);
 

-       thread_set_work_interval(thread, work_interval);
-
-       /* ref was consumed by passing it to the thread */
+       kr = thread_set_work_interval_explicit_join(thread, work_interval);
+       /* ref was consumed by passing it to the thread in the successful case */
+       if (kr != KERN_SUCCESS) {
+               work_interval_release(work_interval, THREAD_WI_THREAD_LOCK_NEEDED);
+       }
+       return kr;
+}

 
 

-       return KERN_SUCCESS;
+/*
+ * work_interval_port_type_render_server()
+ *
+ * Helper routine to determine if the port points to a
+ * WORK_INTERVAL_TYPE_CA_RENDER_SERVER work interval.
+ */
+bool
+work_interval_port_type_render_server(mach_port_name_t port_name)
+{
+       return work_interval_port_type(port_name) == WORK_INTERVAL_TYPE_CA_RENDER_SERVER;

 }
 }