xnu-3789.41.3.tar.gz

[apple/xnu.git] / bsd / kern / kern_proc.c

diff --git a/bsd/kern/kern_proc.c b/bsd/kern/kern_proc.c
index 0d719cb4d84fe5366d0e59393f67ff5887e3755a..3621eeaff01855972c07bf2ec93132d2f1f82a59 100644 (file)
--- a/bsd/kern/kern_proc.c
+++ b/bsd/kern/kern_proc.c
@@ -472,8 +472,22 @@ proc_ref_locked(proc_t p)
        /* if process still in creation return failure */
        if ((p == PROC_NULL) || ((p->p_listflag & P_LIST_INCREATE) != 0))
                        return (PROC_NULL);
-       /* do not return process marked for termination */
-       if ((p->p_stat != SZOMB) && ((p->p_listflag & P_LIST_EXITED) == 0) && ((p->p_listflag & (P_LIST_DRAINWAIT | P_LIST_DRAIN | P_LIST_DEAD)) == 0)) {
+retry:
+       /*
+        * Do not return process marked for termination
+        * or proc_refdrain called without ref wait.
+        * Wait for proc_refdrain_with_refwait to complete if
+        * process in refdrain and refwait flag is set.
+        */
+       if ((p->p_stat != SZOMB) &&
+           ((p->p_listflag & P_LIST_EXITED) == 0) &&
+           ((p->p_listflag & P_LIST_DEAD) == 0) &&
+           (((p->p_listflag & (P_LIST_DRAIN | P_LIST_DRAINWAIT)) == 0) ||
+            ((p->p_listflag & P_LIST_REFWAIT) != 0))) {
+               if ((p->p_listflag & P_LIST_REFWAIT) != 0) {
+                       msleep(&p->p_listflag, proc_list_mlock, 0, "proc_refwait", 0) ;
+                       goto retry;
+               }
                p->p_refcount++;
 #if PROC_REF_DEBUG
                record_procref(p, 1);
@@ -549,20 +563,59 @@ proc_drop_zombref(proc_t p)
 void
 proc_refdrain(proc_t p)
 {
+       proc_refdrain_with_refwait(p, FALSE);
+}
 
+proc_t
+proc_refdrain_with_refwait(proc_t p, boolean_t get_ref_and_allow_wait)
+{
+       boolean_t initexec = FALSE;
        proc_list_lock();
 
        p->p_listflag |= P_LIST_DRAIN;
-       while (p->p_refcount) {
+       if (get_ref_and_allow_wait) {
+               /*
+                * All the calls to proc_ref_locked will wait
+                * for the flag to get cleared before returning a ref.
+                */
+               p->p_listflag |= P_LIST_REFWAIT;
+               if (p == initproc) {
+                       initexec = TRUE;
+               }
+       }
+
+       /* Do not wait in ref drain for launchd exec */
+       while (p->p_refcount && !initexec) {
                p->p_listflag |= P_LIST_DRAINWAIT;
                msleep(&p->p_refcount, proc_list_mlock, 0, "proc_refdrain", 0) ;
        }
+
        p->p_listflag &= ~P_LIST_DRAIN;
-       p->p_listflag |= P_LIST_DEAD;
+       if (!get_ref_and_allow_wait) {
+               p->p_listflag |= P_LIST_DEAD;
+       } else {
+               /* Return a ref to the caller */
+               p->p_refcount++;
+#if PROC_REF_DEBUG
+               record_procref(p, 1);
+#endif
+       }
 
        proc_list_unlock();
 
+       if (get_ref_and_allow_wait) {
+               return (p);
+       }
+       return NULL;
+}
 
+void
+proc_refwake(proc_t p)
+{
+       proc_list_lock();
+       p->p_listflag &= ~P_LIST_REFWAIT;
+       wakeup(&p->p_listflag);
+       proc_list_unlock();
 }
 
 proc_t