- Close races with signals and other AST's being triggered while we are in

  the process of exiting the kernel.  The ast() function now loops as long
  as the PS_ASTPENDING or PS_NEEDRESCHED flags are set.  It returns with
  preemption disabled so that any further AST's that arrive via an
  interrupt will be delayed until the low-level MD code returns to user
  mode.
- Use u_int's to store the tick counts for profiling purposes so that we
  do not need sched_lock just to read p_sticks.  This also closes a
  problem where the call to addupc_task() could screw up the arithmetic
  due to non-atomic reads of p_sticks.
- Axe need_proftick(), aston(), astoff(), astpending(), need_resched(),
  clear_resched(), and resched_wanted() in favor of direct bit operations
  on p_sflag.
- Fix up locking with sched_lock some.  In addupc_intr(), use sched_lock
  to ensure pr_addr and pr_ticks are updated atomically with setting
  PS_OWEUPC.  In ast() we clear pr_ticks atomically with clearing
  PS_OWEUPC.  We also do not grab the lock just to test a flag.
- Simplify the handling of Giant in ast() slightly.

Reviewed by:	bde (mostly)

1 files changed, 3 insertions, 1 deletions

diff --git a/sys/kern/subr_prof.c b/sys/kern/subr_prof.c
index 18c2863799cb..015f6669447a 100644
--- a/sys/kern/subr_prof.c
+++ b/sys/kern/subr_prof.c
@@ -422,9 +422,11 @@ addupc_intr(p, pc, ticks)
 
 	addr = prof->pr_base + i;
 	if ((v = fuswintr(addr)) == -1 || suswintr(addr, v + ticks) == -1) {
+		mtx_lock_spin(&sched_lock);
 		prof->pr_addr = pc;
 		prof->pr_ticks = ticks;
-		need_proftick(p);
+		p->p_sflag |= PS_OWEUPC | PS_ASTPENDING;
+		mtx_unlock_spin(&sched_lock);
 	}
 }