Fix delivery of SIGPROF and SIGVTALRM to threaded processes by having

hardclock() set a flag on the running thread and force AST processing,
and then have the thread signal itself from userret().

idea and flag names from FreeBSD
ok jsing@

1 files changed, 12 insertions, 37 deletions

diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c
index 3d517b0c11b..3f1cdef2e6e 100644
--- a/sys/kern/kern_clock.c
+++ b/sys/kern/kern_clock.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_clock.c,v 1.82 2013/08/13 05:52:23 guenther Exp $	*/
+/*	$OpenBSD: kern_clock.c,v 1.83 2013/10/08 03:50:07 guenther Exp $	*/
 /*	$NetBSD: kern_clock.c,v 1.34 1996/06/09 04:51:03 briggs Exp $	*/
 
 /*-
@@ -144,40 +144,11 @@ initclocks(void)
 /*
  * hardclock does the accounting needed for ITIMER_PROF and ITIMER_VIRTUAL.
  * We don't want to send signals with psignal from hardclock because it makes
- * MULTIPROCESSOR locking very complicated. Instead we use a small trick
- * to send the signals safely and without blocking too many interrupts
- * while doing that (signal handling can be heavy).
- *
- * hardclock detects that the itimer has expired, and schedules a timeout
- * to deliver the signal. This works because of the following reasons:
- *  - The timeout can be scheduled with a 1 tick time because we're
- *    doing it before the timeout processing in hardclock. So it will
- *    be scheduled to run as soon as possible.
- *  - The timeout will be run in softclock which will run before we
- *    return to userland and process pending signals.
- *  - If the system is so busy that several VIRTUAL/PROF ticks are
- *    sent before softclock processing, we'll send only one signal.
- *    But if we'd send the signal from hardclock only one signal would
- *    be delivered to the user process. So userland will only see one
- *    signal anyway.
+ * MULTIPROCESSOR locking very complicated. Instead, to use an idea from
+ * FreeBSD, we set a flag on the thread and when it goes to return to
+ * userspace it signals itself.
  */
 
-void
-virttimer_trampoline(void *v)
-{
-	struct process *pr = v;
-
-	psignal(pr->ps_mainproc, SIGVTALRM);
-}
-
-void
-proftimer_trampoline(void *v)
-{
-	struct process *pr = v;
-
-	psignal(pr->ps_mainproc, SIGPROF);
-}
-
 /*
  * The real-time timer, interrupting hz times per second.
  */
@@ -196,11 +167,15 @@ hardclock(struct clockframe *frame)
 		 */
 		if (CLKF_USERMODE(frame) &&
 		    timerisset(&pr->ps_timer[ITIMER_VIRTUAL].it_value) &&
-		    itimerdecr(&pr->ps_timer[ITIMER_VIRTUAL], tick) == 0)
-			timeout_add(&pr->ps_virt_to, 1);
+		    itimerdecr(&pr->ps_timer[ITIMER_VIRTUAL], tick) == 0) {
+			atomic_setbits_int(&p->p_flag, P_ALRMPEND);
+			need_proftick(p);
+		}
 		if (timerisset(&pr->ps_timer[ITIMER_PROF].it_value) &&
-		    itimerdecr(&pr->ps_timer[ITIMER_PROF], tick) == 0)
-			timeout_add(&pr->ps_prof_to, 1);
+		    itimerdecr(&pr->ps_timer[ITIMER_PROF], tick) == 0) {
+			atomic_setbits_int(&p->p_flag, P_PROFPEND);
+			need_proftick(p);
+		}
 	}
 
 	/*