[PATCH 1/7] [hrtimers] Fixup itimer conversion

[Thomas Gleixner]

The itimer conversion removed the locking which protects
the timer and variables in the shared signal structure.
Steven Rostedt found the problem in the latest -rt patches.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

---

 kernel/itimer.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

52ae41e3d11d6f1828c5827861b7b83b7e854222
diff --git a/kernel/itimer.c b/kernel/itimer.c
index c2c05c4..6433d06 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -49,9 +49,11 @@ int do_getitimer(int which, struct itime
 
 	switch (which) {
 	case ITIMER_REAL:
+		spin_lock_irq(&tsk->sighand->siglock);
 		value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
 		value->it_interval =
 			ktime_to_timeval(tsk->signal->it_real_incr);
+		spin_unlock_irq(&tsk->sighand->siglock);
 		break;
 	case ITIMER_VIRTUAL:
 		read_lock(&tasklist_lock);
@@ -150,8 +152,14 @@ int do_setitimer(int which, struct itime
 
 	switch (which) {
 	case ITIMER_REAL:
+again:
+		spin_lock_irq(&tsk->sighand->siglock);
 		timer = &tsk->signal->real_timer;
-		hrtimer_cancel(timer);
+		/* We are sharing ->siglock with it_real_fn() */
+		if (hrtimer_try_to_cancel(timer) < 0) {
+			spin_unlock_irq(&tsk->sighand->siglock);
+			goto again;
+		}
 		if (ovalue) {
 			ovalue->it_value = itimer_get_remtime(timer);
 			ovalue->it_interval
@@ -162,6 +170,7 @@ int do_setitimer(int which, struct itime
 		expires = timeval_to_ktime(value->it_value);
 		if (expires.tv64 != 0)
 			hrtimer_start(timer, expires, HRTIMER_REL);
+		spin_unlock_irq(&tsk->sighand->siglock);
 		break;
 	case ITIMER_VIRTUAL:
 		nval = timeval_to_cputime(&value->it_value);
-- 
1.0.8

--

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/