[PATCH] netdev: Fix sleeping inside wait event
From: Peter Zijlstra
Date: Wed Oct 29 2014 - 12:17:12 EST
On Tue, Oct 28, 2014 at 10:25:41PM +0800, Fengguang Wu wrote:
> [ 122.247299] ------------[ cut here ]------------
> [ 122.247328] WARNING: CPU: 0 PID: 61 at kernel/sched/core.c:7312 __might_sleep+0x50/0x249()
> [ 122.247334] do not call blocking ops when !TASK_RUNNING; state=2 set at [<c106ffd9>] prepare_to_wait+0x3c/0x5f
> [ 122.247339] Modules linked in:
> [ 122.247349] CPU: 0 PID: 61 Comm: kworker/u2:1 Not tainted 3.18.0-rc2-00037-g24574709 #136
> [ 122.247350] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
> [ 122.247368] Workqueue: netns cleanup_net
> [ 122.247377] c1071d83 d2b83dd8 d2b83dac c15887b1 d2b83dc8 c104c4c6 00001c90 c1068ebf
> [ 122.247383] 00000000 c17b67e3 0000026d d2b83de0 c104c508 00000009 d2b83dd8 c17b5d4b
> [ 122.247388] d2b83df4 d2b83e0c c1068ebf c17b5cec 00001c90 c17b5d4b 00000002 c106ffd9
> [ 122.247389] Call Trace:
> [ 122.247393] [<c1071d83>] ? down_trylock+0x23/0x2c
> [ 122.247402] [<c15887b1>] dump_stack+0x16/0x18
> [ 122.247413] [<c104c4c6>] warn_slowpath_common+0x66/0x7d
> [ 122.247416] [<c1068ebf>] ? __might_sleep+0x50/0x249
> [ 122.247419] [<c104c508>] warn_slowpath_fmt+0x2b/0x2f
> [ 122.247422] [<c1068ebf>] __might_sleep+0x50/0x249
> [ 122.247424] [<c106ffd9>] ? prepare_to_wait+0x3c/0x5f
> [ 122.247426] [<c106ffd9>] ? prepare_to_wait+0x3c/0x5f
> [ 122.247432] [<c158c364>] mutex_lock_nested+0x23/0x347
> [ 122.247436] [<c1075105>] ? trace_hardirqs_on+0xb/0xd
> [ 122.247439] [<c158eb0c>] ? _raw_spin_unlock_irqrestore+0x66/0x78
> [ 122.247445] [<c1570e10>] rtnl_lock+0x14/0x16
> [ 122.247449] [<c156516b>] default_device_exit_batch+0x54/0xf3
> [ 122.247452] [<c1570e1f>] ? rtnl_unlock+0xd/0xf
> [ 122.247454] [<c1070233>] ? __wake_up_sync+0x12/0x12
> [ 122.247461] [<c155e35d>] ops_exit_list+0x20/0x40
> [ 122.247464] [<c155ec96>] cleanup_net+0xbe/0x140
> [ 122.247473] [<c105ffe4>] process_one_work+0x29e/0x643
> [ 122.247479] [<c1061215>] worker_thread+0x23a/0x311
> [ 122.247482] [<c1060fdb>] ? rescuer_thread+0x204/0x204
> [ 122.247486] [<c10648cc>] kthread+0xbe/0xc3
> [ 122.247490] [<c158f4c0>] ret_from_kernel_thread+0x20/0x30
> [ 122.247492] [<c106480e>] ? kthread_stop+0x364/0x364
> [ 122.247495] ---[ end trace 2073c37ae3c8b3b4 ]---
Ah, more of that. Thanks!
Dave, this relies on bits currently in tip/sched/core, if you're ok I'll
merge it through that tree.
---
Subject: netdev: Fix sleeping inside wait event
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Wed Oct 29 17:04:56 CET 2014
rtnl_lock_unregistering() takes rtnl_lock() -- a mutex -- inside a
wait loop. The wait loop relies on current->state to function, but so
does mutex_lock(), nesting them makes for the inner to destroy the
outer state.
Fix this using the new wait_woken() bits.
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: David Miller <davem@xxxxxxxxxxxxx>
Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
net/core/dev.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7196,11 +7196,10 @@ static void __net_exit rtnl_lock_unregis
*/
struct net *net;
bool unregistering;
- DEFINE_WAIT(wait);
+ DEFINE_WAIT_FUNC(wait, woken_wake_function);
+ add_wait_queue(&netdev_unregistering_wq, &wait);
for (;;) {
- prepare_to_wait(&netdev_unregistering_wq, &wait,
- TASK_UNINTERRUPTIBLE);
unregistering = false;
rtnl_lock();
list_for_each_entry(net, net_list, exit_list) {
@@ -7212,9 +7211,10 @@ static void __net_exit rtnl_lock_unregis
if (!unregistering)
break;
__rtnl_unlock();
- schedule();
+
+ wait_woken(&wait, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
}
- finish_wait(&netdev_unregistering_wq, &wait);
+ remove_wait_queue(&netdev_unregistering_wq, &wait);
}
static void __net_exit default_device_exit_batch(struct list_head *net_list)
--
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