lkml.org 
[lkml]   [2008]   [Aug]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 1/3] posix-timers: don't switch to ->group_leader if ->it_process dies
(textually depends on posix-timers-fix-posix_timer_event-vs-dequeue_signal-race.patch)

posix_timer_event() drops SIGEV_THREAD_ID and switches to ->group_leader if
send_sigqueue() fails.

This is not very useful and doesn't work reliably. send_sigqueue() can only
fail if ->it_process is dead. But it can die before it dequeues the SI_TIMER
signal, in that case the timer stops anyway.

Remove this code. I guess it was needed a long ago to ensure that the timer
is not destroyed when when its creator thread dies.

Q: perhaps it makes sense to change sys_timer_settime() to return an error
if ->it_process is dead?

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

--- 26-rc2/kernel/posix-timers.c~1_DONT_RESEND 2008-07-23 20:24:05.000000000 +0400
+++ 26-rc2/kernel/posix-timers.c 2008-08-03 20:25:41.000000000 +0400
@@ -298,6 +298,7 @@ void do_schedule_next_timer(struct sigin

int posix_timer_event(struct k_itimer *timr, int si_private)
{
+ int shared, ret;
/*
* FIXME: if ->sigq is queued we can race with
* dequeue_signal()->do_schedule_next_timer().
@@ -316,20 +317,10 @@ int posix_timer_event(struct k_itimer *t
timr->sigq->info.si_tid = timr->it_id;
timr->sigq->info.si_value = timr->it_sigev_value;

- if (timr->it_sigev_notify & SIGEV_THREAD_ID) {
- struct task_struct *leader;
- int ret = send_sigqueue(timr->sigq, timr->it_process, 0);
-
- if (likely(ret >= 0))
- return ret;
-
- timr->it_sigev_notify = SIGEV_SIGNAL;
- leader = timr->it_process->group_leader;
- put_task_struct(timr->it_process);
- timr->it_process = leader;
- }
-
- return send_sigqueue(timr->sigq, timr->it_process, 1);
+ shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);
+ ret = send_sigqueue(timr->sigq, timr->it_process, shared);
+ /* If we failed to send the signal the timer stops. */
+ return ret > 0;
}
EXPORT_SYMBOL_GPL(posix_timer_event);



\
 
 \ /
  Last update: 2008-08-03 19:49    [from the cache]
©2003-2011 Jasper Spaans