From: Oleg Nesterov Date: Thu, 15 Jun 2006 16:11:43 +0000 (+0400) Subject: [PATCH] run_posix_cpu_timers: remove a bogus BUG_ON() X-Git-Tag: v2.6.17~4 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=30f1e3dd8c72abda343bcf415f7d8894a02b4290;p=pandora-kernel.git [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 Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed