Re: [setsockopt] WARNING: CPU: 0 PID: 1444 at kernel/sched/core.c:7088 __might_sleep+0x51/0x16f()

Subject: atm: Fix blocking in wait loop

One should not call blocking primitives inside a wait loop, since both
require task_struct::state to sleep, so the inner will destroy the outer
state.

In this instance sigd_enq() will possible sleep for alloc_skb(), now if
I understand the code right, we do not actually need to call sigd_enq()
after the initial prepare_to_wait(), because we test the termination
condition before schedule() anyhow.

So we can simply move it up a bit and avoid the entire confusion.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
 net/atm/svc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/atm/svc.c b/net/atm/svc.c
index d8e5d0c2ebbc..445ac238b69b 100644
--- a/net/atm/svc.c
+++ b/net/atm/svc.c

@@ -297,8 +297,8 @@ static int svc_listen(struct socket *sock, int backlog)
 		goto out;
 	}
 	set_bit(ATM_VF_WAITING, &vcc->flags);
-	prepare_to_wait(sk_sleep(sk), &wait, TASK_UNINTERRUPTIBLE);
 	sigd_enq(vcc, as_listen, NULL, NULL, &vcc->local);
+	prepare_to_wait(sk_sleep(sk), &wait, TASK_UNINTERRUPTIBLE);
 	while (test_bit(ATM_VF_WAITING, &vcc->flags) && sigd) {
 		schedule();
 		prepare_to_wait(sk_sleep(sk), &wait, TASK_UNINTERRUPTIBLE);