[PATCH] make __sigqueue_alloc() a general helper

Posix timers preallocate siqueue structures during timer creation
and keep them for reuse.  This allocation happens in user context
with no locks held, however it's designated as an atomic allocation.
Loosen this restriction, and while we're at it let's do a bit of code
consolidation so signal sending uses same __sigqueue_alloc() helper.
Signed-off-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/signal.c

@@ -265,18 +265,18 @@ next_signal(struct sigpending *pending, sigset_t *mask)
 	return sig;
 }
 
-static struct sigqueue *__sigqueue_alloc(void)
+static inline struct sigqueue *__sigqueue_alloc(struct task_struct *t, int flags)
 {
 	struct sigqueue *q = NULL;
 
-	if (atomic_read(&current->user->sigpending) <
-			current->signal->rlim[RLIMIT_SIGPENDING].rlim_cur)
-		q = kmem_cache_alloc(sigqueue_cachep, GFP_ATOMIC);
+	if (atomic_read(&t->user->sigpending) <
+			t->signal->rlim[RLIMIT_SIGPENDING].rlim_cur)
+		q = kmem_cache_alloc(sigqueue_cachep, flags);
 	if (q) {
 		INIT_LIST_HEAD(&q->list);
 		q->flags = 0;
 		q->lock = NULL;
-		q->user = get_uid(current->user);
+		q->user = get_uid(t->user);
 		atomic_inc(&q->user->sigpending);
 	}
 	return(q);
@@ -764,14 +764,8 @@ static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
 	   make sure at least one signal gets delivered and don't
 	   pass on the info struct.  */
 
-	if (atomic_read(&t->user->sigpending) <
-			t->signal->rlim[RLIMIT_SIGPENDING].rlim_cur)
-		q = kmem_cache_alloc(sigqueue_cachep, GFP_ATOMIC);
-
+	q = __sigqueue_alloc(t, GFP_ATOMIC);
 	if (q) {
-		q->flags = 0;
-		q->user = get_uid(t->user);
-		atomic_inc(&q->user->sigpending);
 		list_add_tail(&q->list, &signals->list);
 		switch ((unsigned long) info) {
 		case 0:
@@ -1298,7 +1292,7 @@ struct sigqueue *sigqueue_alloc(void)
 {
 	struct sigqueue *q;
 
-	if ((q = __sigqueue_alloc()))
+	if ((q = __sigqueue_alloc(current, GFP_KERNEL)))
 		q->flags |= SIGQUEUE_PREALLOC;
 	return(q);
 }