From mboxrd@z Thu Jan 1 00:00:00 1970 From: chas williams - CONTRACTOR Subject: Re: [setsockopt] WARNING: CPU: 0 PID: 1444 at kernel/sched/core.c:7088 __might_sleep+0x51/0x16f() Date: Thu, 7 Aug 2014 12:59:48 -0400 Message-ID: <20140807125948.2b7f1472@thirdoffive.cmf.nrl.navy.mil> References: <20140805214624.GA9973@localhost> <20140807151741.GP19379@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Fengguang Wu , netdev@vger.kernel.org, LKML , lkp@01.org, linux-atm-general@lists.sourceforge.net To: Peter Zijlstra Return-path: In-Reply-To: <20140807151741.GP19379@twins.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, 7 Aug 2014 17:17:41 +0200 Peter Zijlstra wrote: > 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 > --- > 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); This isn't the only place that we queue a message for the signalling daemon after a prepare_to_wait() uninterruptibly so this patch would be incomplete as is. What bothers me is the TASK_UNINTERRUPTIBLE -- I don't have a good reason why any of these should be sleeping uninterruptibly.