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[PATCH] Call exit_itimers from do_exit, not __exit_signal 

When I originally moved exit_itimers into __exit_signal, that was the only
place where we could reliably know it was the last thread in the group
dying, without races.  Since then we've gotten the signal_struct.live
counter, and do_exit can reliably do group-wide cleanup work.

This patch moves the call to do_exit, where it's made without locks.  This
avoids the deadlock issues that the old __exit_signal code's comment talks
about, and the one that Oleg found recently with process CPU timers.

[ This replaces e03d13e985, which is why
  it was just reverted. ]

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Roland McGrath 2005-10-21 15:03:29 -07:00 committed by Linus Torvalds
parent 9465bee863
commit 25f407f0b6
3 changed files with 3 additions and 14 deletions
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1
kernel/exit.c
View File

@ -843,6 +843,7 @@ fastcall NORET_TYPE void do_exit(long code)
group_dead = atomic_dec_and_test(&tsk->signal->live);
if (group_dead) {
del_timer_sync(&tsk->signal->real_timer);
exit_itimers(tsk->signal);
acct_process(code);
}
exit_mm(tsk);

2
kernel/posix-timers.c
View File

@ -1157,7 +1157,7 @@ retry_delete:
}
/*
* This is called by __exit_signal, only when there are no more
* This is called by do_exit or de_thread, only when there are no more
* references to the shared signal_struct.
*/
void exit_itimers(struct signal_struct *sig)

14
kernel/signal.c
View File

@ -397,20 +397,8 @@ void __exit_signal(struct task_struct *tsk)
flush_sigqueue(&tsk->pending);
if (sig) {
/*
* We are cleaning up the signal_struct here. We delayed
* calling exit_itimers until after flush_sigqueue, just in
* case our thread-local pending queue contained a queued
* timer signal that would have been cleared in
* exit_itimers. When that called sigqueue_free, it would
* attempt to re-take the tasklist_lock and deadlock. This
* can never happen if we ensure that all queues the
* timer's signal might be queued on have been flushed
* first. The shared_pending queue, and our own pending
* queue are the only queues the timer could be on, since
* there are no other threads left in the group and timer
* signals are constrained to threads inside the group.
* We are cleaning up the signal_struct here.
*/
exit_itimers(sig);
exit_thread_group_keys(sig);
kmem_cache_free(signal_cachep, sig);
}