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authorOleg Nesterov <oleg@tv-sign.ru>2005-06-28 20:44:47 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-28 21:20:30 -0700
commitf01b1b0baa454825ed95c28d2a6a71bbf4510836 (patch)
tree6a7dda617cdb79933780b841429e67ec7c908d52 /kernel
parentb36bbb6c3d5244eaf52241ec69f79494137f2db0 (diff)
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[PATCH] ITIMER_REAL: fix possible deadlock and race
As Steven Rostedt pointed out, there are 2 problems with ITIMER_REAL timers. 1. do_setitimer() does not call del_timer_sync() in case when the timer is not pending (it_real_value() returns 0). This is wrong, the timer may still be running, and it can rearm itself. 2. It calls del_timer_sync() with tsk->sighand->siglock held. This is deadlockable, because timer's handler needs this lock too. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/itimer.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/kernel/itimer.c b/kernel/itimer.c
index 1dc988e0d2c..a72cb0e5aa4 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -153,11 +153,15 @@ int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
switch (which) {
case ITIMER_REAL:
+again:
spin_lock_irq(&tsk->sighand->siglock);
interval = tsk->signal->it_real_incr;
val = it_real_value(tsk->signal);
- if (val)
- del_timer_sync(&tsk->signal->real_timer);
+ /* We are sharing ->siglock with it_real_fn() */
+ if (try_to_del_timer_sync(&tsk->signal->real_timer) < 0) {
+ spin_unlock_irq(&tsk->sighand->siglock);
+ goto again;
+ }
tsk->signal->it_real_incr =
timeval_to_jiffies(&value->it_interval);
it_real_arm(tsk, timeval_to_jiffies(&value->it_value));