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authorOleg Nesterov <oleg@tv-sign.ru>2006-06-15 20:11:15 +0400
committerChris Wright <chrisw@sous-sol.org>2006-06-20 01:54:52 -0700
commit5705264e83bd9f8918895d8f5ddddbdeb062c719 (patch)
tree11ba63a74fb0907ee686c1c30cd58d95b0f4e555 /kernel
parentad325de56677938d8c58b376e1d7813b50527263 (diff)
downloadlinux-linaro-stable-5705264e83bd9f8918895d8f5ddddbdeb062c719.tar.gz
[PATCH] check_process_timers: fix possible lockup
If the local timer interrupt happens just after do_exit() sets PF_EXITING (and before it clears ->it_xxx_expires) run_posix_cpu_timers() will call check_process_timers() with tasklist_lock + ->siglock held and check_process_timers: t = tsk; do { .... do { t = next_thread(t); } while (unlikely(t->flags & PF_EXITING)); } while (t != tsk); the outer loop will never stop. Actually, the window is bigger. Another process can attach the timer after ->it_xxx_expires was cleared (see the next commit) and the 'if (PF_EXITING)' check in arm_timer() is racy (see the one after that). Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Linus Torvalds <torvalds@osdl.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/posix-cpu-timers.c9
1 files changed, 4 insertions, 5 deletions
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 520f6c59948d..9d9169aa2e24 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1173,6 +1173,9 @@ static void check_process_timers(struct task_struct *tsk,
}
t = tsk;
do {
+ if (unlikely(t->flags & PF_EXITING))
+ continue;
+
ticks = cputime_add(cputime_add(t->utime, t->stime),
prof_left);
if (!cputime_eq(prof_expires, cputime_zero) &&
@@ -1193,11 +1196,7 @@ static void check_process_timers(struct task_struct *tsk,
t->it_sched_expires > sched)) {
t->it_sched_expires = sched;
}
-
- do {
- t = next_thread(t);
- } while (unlikely(t->flags & PF_EXITING));
- } while (t != tsk);
+ } while ((t = next_thread(t)) != tsk);
}
}