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

Greetings,

Here is a microcode/load_module error triggered by debug check commit

Quoted 3 lines · Fengguang Wu

Greetings,

Here is a microcode/load_module error triggered by debug check commit

Sorry for the copy&paste error! This warning is not related to microcode/load_module..

Thanks,
Fengguang
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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 <[email protected]>

---
 net/atm/svc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

net/atm/svc.c +0 -0

index d8e5d0c2ebbc..445ac238b69b 100644

Quoted 29 lines · On Thu, 7 Aug 2014 17:17:41 +0200 Peter Zijlstra <[email protected]> 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 <[email protected]>

---
 net/atm/svc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

net/atm/svc.c +1 -1

index d8e5d0c2ebbc..445ac238b69b 100644
@@ -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);

net/atm/svc.c static int svc_listen(struct socket *sock, int backlog) · line 304

Quoted 3 lines

net/atm/svc.c +0 -0

 	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.

Quoted 3 lines

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.

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.

sigd_enq() will possibly sleep for alloc_skb(). Move sigd_enq() before prepare_to_wait() to avoid sleeping while waiting interruptibly. You do not actually need to call sigd_enq() after the initial prepare_to_wait() because we test the termination condition before calling schedule().

Based on suggestions from Peter Zijlstra.

Signed-off-by Chas Williams <[email protected]>

Acked-by Peter Zijlstra <[email protected]>