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[PATCH] Simpler signal-exit concurrency handling

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Some simplification in checking signal delivery against concurrent exit.
Instead of using get_task_struct_rcu(), which increments the task_struct
reference count, check the reference count after acquiring sighand lock.

Signed-off-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Paul E. McKenney 2006-01-08 01:01:38 -08:00 committed by Linus Torvalds
parent e56d090310
commit 2d89c92907
1 changed files with 6 additions and 5 deletions
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11
kernel/signal.c
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@ -1102,18 +1102,19 @@ int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
retry:
ret = check_kill_permission(sig, info, p);
if (!ret && sig && (sp = p->sighand)) {
if (!get_task_struct_rcu(p))
return -ESRCH;
if (!ret && sig && (sp = rcu_dereference(p->sighand))) {
spin_lock_irqsave(&sp->siglock, flags);
if (p->sighand != sp) {
spin_unlock_irqrestore(&sp->siglock, flags);
put_task_struct(p);
goto retry;
}
if ((atomic_read(&sp->count) == 0) ||
(atomic_read(&p->usage) == 0)) {
spin_unlock_irqrestore(&sp->siglock, flags);
return -ESRCH;
}
ret = __group_send_sig_info(sig, info, p);
spin_unlock_irqrestore(&sp->siglock, flags);
put_task_struct(p);
}
return ret;