[PATCH] Simpler signal-exit concurrency handling
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>
diff --git a/kernel/signal.c b/kernel/signal.c
index 64737c7..9b6fda5 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1102,18 +1102,19 @@
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;
