diff options
author | Oleg Nesterov <oleg@tv-sign.ru> | 2008-02-08 12:19:12 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-08 17:22:27 (GMT) |
commit | d12619b5ff5664623524aef796514d1946ea3b4a (patch) | |
tree | 23140ca0148f9154440d3056e2040d8df468a24b /kernel/signal.c | |
parent | 430c623121ea88ca80595c99fdc63b7f8a803ae5 (diff) | |
download | linux-fsl-qoriq-d12619b5ff5664623524aef796514d1946ea3b4a.tar.xz |
fix group stop with exit race
do_signal_stop() counts all sub-thread and sets ->group_stop_count
accordingly. Every thread should decrement ->group_stop_count and stop,
the last one should notify the parent.
However a sub-thread can exit before it notices the signal_pending(), or it
may be somewhere in do_exit() already. In that case the group stop never
finishes properly.
Note: this is a minimal fix, we can add some optimizations later. Say we
can return quickly if thread_group_empty(). Also, we can move some signal
related code from exit_notify() to exit_signals().
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/signal.c')
-rw-r--r-- | kernel/signal.c | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/kernel/signal.c b/kernel/signal.c index 3fca710..209eec1 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1739,7 +1739,7 @@ static int do_signal_stop(int signr) * stop is always done with the siglock held, * so this check has no races. */ - if (!t->exit_state && + if (!(t->flags & PF_EXITING) && !task_is_stopped_or_traced(t)) { stop_count++; signal_wake_up(t, 0); @@ -1900,6 +1900,31 @@ relock: return signr; } +void exit_signals(struct task_struct *tsk) +{ + int group_stop = 0; + + spin_lock_irq(&tsk->sighand->siglock); + if (unlikely(tsk->signal->group_stop_count) && + !--tsk->signal->group_stop_count) { + tsk->signal->flags = SIGNAL_STOP_STOPPED; + group_stop = 1; + } + + /* + * From now this task is not visible for group-wide signals, + * see wants_signal(), do_signal_stop(). + */ + tsk->flags |= PF_EXITING; + spin_unlock_irq(&tsk->sighand->siglock); + + if (unlikely(group_stop)) { + read_lock(&tasklist_lock); + do_notify_parent_cldstop(tsk, CLD_STOPPED); + read_unlock(&tasklist_lock); + } +} + EXPORT_SYMBOL(recalc_sigpending); EXPORT_SYMBOL_GPL(dequeue_signal); EXPORT_SYMBOL(flush_signals); |