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authorOleg Nesterov <oleg@tv-sign.ru>2005-10-24 14:34:03 +0400
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-24 08:12:35 -0700
commit3de463c7d9d58f8cf3395268230cb20a4c15bffa (patch)
tree20ba1584eefb7ed75f6f8536f40e55966294cf4f
parent108150ea78003044e41150c75259447b2c0953b6 (diff)
[PATCH] posix-timers: remove false BUG_ON() from run_posix_cpu_timers()
do_exit() clears ->it_##clock##_expires, but nothing prevents another cpu to attach the timer to exiting process after that. After exit_notify() does 'write_unlock_irq(&tasklist_lock)' and before do_exit() calls 'schedule() local timer interrupt can find tsk->exit_state != 0. If that state was EXIT_DEAD (or another cpu does sys_wait4) interrupted task has ->signal == NULL. At this moment exiting task has no pending cpu timers, they were cleaned up in __exit_signal()->posix_cpu_timers_exit{,_group}(), so we can just return from irq. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--kernel/exit.c8
-rw-r--r--kernel/posix-cpu-timers.c36
2 files changed, 18 insertions, 26 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 3b25b182d2be..4897977a1f4b 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -825,14 +825,6 @@ fastcall NORET_TYPE void do_exit(long code)
tsk->flags |= PF_EXITING;
- /*
- * Make sure we don't try to process any timer firings
- * while we are already exiting.
- */
- tsk->it_virt_expires = cputime_zero;
- tsk->it_prof_expires = cputime_zero;
- tsk->it_sched_expires = 0;
-
if (unlikely(in_atomic()))
printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
current->comm, current->pid,
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 30ab39a27736..ccb04683bf18 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1285,30 +1285,30 @@ void run_posix_cpu_timers(struct task_struct *tsk)
#undef UNEXPIRED
- BUG_ON(tsk->exit_state);
-
/*
* Double-check with locks held.
*/
read_lock(&tasklist_lock);
- spin_lock(&tsk->sighand->siglock);
+ if (likely(tsk->signal != NULL)) {
+ spin_lock(&tsk->sighand->siglock);
- /*
- * Here we take off tsk->cpu_timers[N] and tsk->signal->cpu_timers[N]
- * all the timers that are firing, and put them on the firing list.
- */
- check_thread_timers(tsk, &firing);
- check_process_timers(tsk, &firing);
+ /*
+ * Here we take off tsk->cpu_timers[N] and tsk->signal->cpu_timers[N]
+ * all the timers that are firing, and put them on the firing list.
+ */
+ check_thread_timers(tsk, &firing);
+ check_process_timers(tsk, &firing);
- /*
- * We must release these locks before taking any timer's lock.
- * There is a potential race with timer deletion here, as the
- * siglock now protects our private firing list. We have set
- * the firing flag in each timer, so that a deletion attempt
- * that gets the timer lock before we do will give it up and
- * spin until we've taken care of that timer below.
- */
- spin_unlock(&tsk->sighand->siglock);
+ /*
+ * We must release these locks before taking any timer's lock.
+ * There is a potential race with timer deletion here, as the
+ * siglock now protects our private firing list. We have set
+ * the firing flag in each timer, so that a deletion attempt
+ * that gets the timer lock before we do will give it up and
+ * spin until we've taken care of that timer below.
+ */
+ spin_unlock(&tsk->sighand->siglock);
+ }
read_unlock(&tasklist_lock);
/*