]> pilppa.com Git - linux-2.6-omap-h63xx.git/commit
[PATCH] run_posix_cpu_timers: remove a bogus BUG_ON()
authorOleg Nesterov <oleg@tv-sign.ru>
Thu, 15 Jun 2006 16:11:43 +0000 (20:11 +0400)
committerLinus Torvalds <torvalds@g5.osdl.org>
Sat, 17 Jun 2006 17:52:13 +0000 (10:52 -0700)
commit30f1e3dd8c72abda343bcf415f7d8894a02b4290
tree68ef326814e3b8e6ba0159cc451cef4b71695ea3
parent8f17fc20bfb75bcec4cfeda789738979c8338fdc
[PATCH] run_posix_cpu_timers: remove a bogus BUG_ON()

do_exit() clears ->it_##clock##_expires, but nothing prevents
another cpu to attach the timer to exiting process after that.
arm_timer() tries to protect against this race, but the check
is racy.

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
cleanuped in __exit_signal()->posix_cpu_timers_exit{,_group}(),
so we can just return from irq.

John Stultz recently confirmed this bug, see

http://marc.theaimsgroup.com/?l=linux-kernel&m=115015841413687

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
kernel/exit.c
kernel/posix-cpu-timers.c