From 25f407f0b668f5e4ebd5d13e1fb4306ba6427ead Mon Sep 17 00:00:00 2001 From: Roland McGrath Date: Fri, 21 Oct 2005 15:03:29 -0700 Subject: [PATCH] [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 e03d13e985d48ac4885382c9e3b1510c78bd047f, which is why it was just reverted. ] Signed-off-by: Roland McGrath Signed-off-by: Linus Torvalds --- kernel/exit.c | 1 + kernel/posix-timers.c | 2 +- kernel/signal.c | 14 +------------- 3 files changed, 3 insertions(+), 14 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index 43077732619b..3b25b182d2be 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -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); diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c index b7b532acd9fc..dda3cda73c77 100644 --- a/kernel/posix-timers.c +++ b/kernel/posix-timers.c @@ -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) diff --git a/kernel/signal.c b/kernel/signal.c index 50c992643771..f2b96b08fb44 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -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); } -- 2.20.1