- Move the second stop() of process 'p' in issignal() to be after we send

  SIGCHLD to our parent process.  Otherwise, we could block while obtaining
  the process lock for our parent process and switch out while we were
  in SSTOP.  Even worse, when we try to resume from the mutex being blocked
  on our p_stat will be SRUN, not SSTOP.
- Fix a comment above stop() to indicate that it requires that the proc lock
  be held, not a proctree lock.

Reported by:	markm
Sleuthing by:	jake

1 files changed, 2 insertions, 3 deletions

diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index c529410..3429f39 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -1469,12 +1469,12 @@ issignal(p)
 				    prop & SA_TTYSTOP))
 					break;	/* == ignore */
 				p->p_xstat = sig;
-				stop(p);
 				if ((p->p_pptr->p_procsig->ps_flag & PS_NOCLDSTOP) == 0) {
 					PROC_LOCK(p->p_pptr);
 					psignal(p->p_pptr, SIGCHLD);
 					PROC_UNLOCK(p->p_pptr);
 				}
+				stop(p);
 				mtx_lock_spin(&sched_lock);
 				PROC_UNLOCK_NOSWITCH(p);
 				DROP_GIANT_NOSWITCH();
@@ -1519,8 +1519,7 @@ issignal(p)
 /*
  * Put the argument process into the stopped state and notify the parent
  * via wakeup.  Signals are handled elsewhere.  The process must not be
- * on the run queue.  Must be called with at least a shared hold of the
- * proctree lock.
+ * on the run queue.  Must be called with the proc p locked.
  */
 void
 stop(p)