[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:
parent
9465bee863
commit
25f407f0b6
3 changed files with 3 additions and 14 deletions
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@ -843,6 +843,7 @@ fastcall NORET_TYPE void do_exit(long code)
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group_dead = atomic_dec_and_test(&tsk->signal->live);
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if (group_dead) {
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del_timer_sync(&tsk->signal->real_timer);
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exit_itimers(tsk->signal);
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acct_process(code);
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}
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exit_mm(tsk);
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@ -1157,7 +1157,7 @@ static inline void itimer_delete(struct k_itimer *timer)
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}
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/*
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* This is called by __exit_signal, only when there are no more
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* This is called by do_exit or de_thread, only when there are no more
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* references to the shared signal_struct.
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*/
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void exit_itimers(struct signal_struct *sig)
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@ -397,20 +397,8 @@ void __exit_signal(struct task_struct *tsk)
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flush_sigqueue(&tsk->pending);
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if (sig) {
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/*
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* We are cleaning up the signal_struct here. We delayed
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* calling exit_itimers until after flush_sigqueue, just in
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* case our thread-local pending queue contained a queued
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* timer signal that would have been cleared in
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* exit_itimers. When that called sigqueue_free, it would
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* attempt to re-take the tasklist_lock and deadlock. This
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* can never happen if we ensure that all queues the
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* timer's signal might be queued on have been flushed
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* first. The shared_pending queue, and our own pending
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* queue are the only queues the timer could be on, since
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* there are no other threads left in the group and timer
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* signals are constrained to threads inside the group.
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* We are cleaning up the signal_struct here.
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*/
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exit_itimers(sig);
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exit_thread_group_keys(sig);
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kmem_cache_free(signal_cachep, sig);
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}
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