[PATCH 1/3] signals: sigqueue_free: don't free sigqueue if it is queued

From: Oleg Nesterov
Date: Sat May 17 2008 - 11:15:47 EST

Currently sigqueue_free() removes sigqueue from list, but doesn't cancel the
pending signal. This is not consistent, the task should either receive the
"full" signal along with siginfo_t, or it shouldn't receive the signal at all.

Change sigqueue_free() to clear SIGQUEUE_PREALLOC but leave sigqueue on list
if it is queued.

This patch doesn't change the behaviour of sys_timer_delete() and friends,
just makes it more correct and allows us to introduce other SIGQUEUE_ flags
passed to the receiver.

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>

--- 25/kernel/signal.c~4_SF_DONT_REMOVE 2008-05-17 16:22:07.000000000 +0400
+++ 25/kernel/signal.c 2008-05-17 17:14:04.000000000 +0400
@@ -1240,18 +1240,22 @@ void sigqueue_free(struct sigqueue *q)

- * If the signal is still pending remove it from the
- * pending queue. We must hold ->siglock while testing
- * q->list to serialize with collect_signal() or with
+ * We must hold ->siglock while testing q->list
+ * to serialize with collect_signal() or with
* __exit_signal()->flush_sigqueue().
spin_lock_irqsave(lock, flags);
+ q->flags &= ~SIGQUEUE_PREALLOC;
+ /*
+ * If it is queued it will be freed when dequeued,
+ * like the "regular" sigqueue.
+ */
if (!list_empty(&q->list))
- list_del_init(&q->list);
+ q = NULL;
spin_unlock_irqrestore(lock, flags);

- q->flags &= ~SIGQUEUE_PREALLOC;
- __sigqueue_free(q);
+ if (q)
+ __sigqueue_free(q);

int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)

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