diff mbox

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

Message ID 20140807151741.GP19379@twins.programming.kicks-ass.net
State Changes Requested, archived
Delegated to: David Miller
Headers show

Commit Message

Peter Zijlstra Aug. 7, 2014, 3:17 p.m. UTC 
On Wed, Aug 06, 2014 at 05:46:24AM +0800, Fengguang Wu wrote:
> Greetings,
> 
> Here is a microcode/load_module error triggered by debug check commit
> 64c2181bc433b17f04da8fe8592aa83cceac9606 ("sched: Debug nested sleeps"):
> 
> [main] Setsockopt(1 8 80d1000 4) on fd 21 [1:2:1]
> [main] Setsockopt(1 2f 80d1000 4) on fd 22 [4:2:60]
> [   14.027148] ------------[ cut here ]------------
> [   14.027864] WARNING: CPU: 0 PID: 210 at kernel/sched/core.c:7088 __might_sleep+0x40/0x68()
> [   14.029295] do not call blocking ops when !TASK_RUNNING; state=2 set at [<c144e379>] prepare_to_wait+0x35/0x56
> [   14.030590] Modules linked in:
> [   14.031136] CPU: 0 PID: 210 Comm: trinity-main Not tainted 3.16.0-02167-g254135e #972
> [   14.032263]  00000000 c0f4de4c c0f4de24 c196630c c0f4de3c c142f01a c1447632 c0f1dbb0
> [   14.033480]  00000002 b0066140 c0f4de54 c142f057 00000009 c0f4de4c c1b3bac8 c0f4de68
> [   14.034640]  c0f4de88 c1447632 c1b3bb12 00001bb0 c1b3bac8 00000002 c144e379 c144e379
> [   14.035983] Call Trace:
> [   14.036355]  [<c196630c>] dump_stack+0x16/0x18
> [   14.037005]  [<c142f01a>] warn_slowpath_common+0x55/0x6c
> [   14.037715]  [<c1447632>] ? __might_sleep+0x40/0x68
> [   14.038372]  [<c142f057>] warn_slowpath_fmt+0x26/0x2a
> [   14.039097]  [<c1447632>] __might_sleep+0x40/0x68
> [   14.039787]  [<c144e379>] ? prepare_to_wait+0x35/0x56
> [   14.040595]  [<c144e379>] ? prepare_to_wait+0x35/0x56
> [   14.041272]  [<c14a837e>] kmem_cache_alloc+0x39/0xb0
> [   14.041934]  [<c18fa2de>] ? __alloc_skb+0x3c/0x154
> [   14.042572]  [<c18fa2de>] __alloc_skb+0x3c/0x154
> [   14.043339]  [<c145117a>] ? mark_held_locks+0x44/0x60
> [   14.044141]  [<c1946093>] sigd_enq2+0x2a/0xff
> [   14.044836]  [<c1946188>] sigd_enq+0x20/0x2a
> [   14.045405]  [<c19467fb>] svc_listen+0x8b/0x11f
> [   14.046009]  [<c144e5a6>] ? __wake_up_sync+0xd/0xd
> [   14.046653]  [<c18f4132>] SyS_listen+0x37/0x51
> [   14.047423]  [<c18f4ce5>] SyS_socketcall+0x90/0x1c0
> [   14.048328]  [<c145136e>] ? trace_hardirqs_on+0xb/0xd
> [   14.049061]  [<c19729f6>] ? restore_all+0xf/0xf
> [   14.049665]  [<c19729bd>] syscall_call+0x7/0x7
> [   14.050253]  [<c1970000>] ? __ww_mutex_lock_interruptible+0x165/0x573
> [   14.051147] ---[ end trace 6f1365c63eafedde ]---
> [main] Setsockopt(1 2d 80d1000 f0) on fd 25 [1:1:1]

---
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(-)

Comments

chas williams - CONTRACTOR Aug. 7, 2014, 4:59 p.m. UTC | #1 
On Thu, 7 Aug 2014 17:17:41 +0200
Peter Zijlstra <peterz@infradead.org> 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 <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);


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.
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Peter Zijlstra Aug. 7, 2014, 5:25 p.m. UTC | #2 
On Thu, Aug 07, 2014 at 12:59:48PM -0400, chas williams - CONTRACTOR wrote:
> On Thu, 7 Aug 2014 17:17:41 +0200
> Peter Zijlstra <peterz@infradead.org> 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 <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);
> 
> 
> 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.

I'm not sure I follow, this is the only place you do so while then going
to sleep. All other sites don't sleep while they're enqueued on the
waitqueue.

> What bothers me is the TASK_UNINTERRUPTIBLE -- I don't have a good
> reason why any of these should be sleeping uninterruptibly.

That's a whole different story, there's tons of ugly in there, but its
all ancient code.
Peter Zijlstra Aug. 7, 2014, 5:29 p.m. UTC | #3 
On Thu, Aug 07, 2014 at 07:25:14PM +0200, Peter Zijlstra wrote:
> > 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.
> 
> I'm not sure I follow, this is the only place you do so while then going
> to sleep. All other sites don't sleep while they're enqueued on the
> waitqueue.

Argh, my brain is fried, you're quite right.  I'll go have another stab
at it tomorrow or so.
diff mbox

Patch

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);