linux-kernel - Re: [Linux v4.2] workqueue: llvmlinux: acpid: BUG: sleeping function called from invalid context at kernel/workqueue.c:2680

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Message-ID: <alpine.LRH.2.00.1509241001180.16560@twin.jikos.cz>
Date:	Thu, 24 Sep 2015 10:03:04 +0200 (CEST)
From:	Jiri Kosina <jikos@...nel.org>
To:	Sedat Dilek <sedat.dilek@...il.com>
cc:	Tejun Heo <tj@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Darren Hart <dvhart@...ux.intel.com>,
	Lai Jiangshan <jiangshanlai@...il.com>
Subject: Re: [Linux v4.2] workqueue: llvmlinux: acpid: BUG: sleeping function
 called from invalid context at kernel/workqueue.c:2680

On Thu, 24 Sep 2015, Jiri Kosina wrote:

> > >> [   24.705767]  [<ffffffff8149287d>] dump_stack+0x7d/0xa0
> > >> [   24.705774]  [<ffffffff810cbf7a>] ___might_sleep+0x28a/0x2a0
> > >> [   24.705779]  [<ffffffff810cbc7f>] __might_sleep+0x4f/0xc0
> > >> [   24.705784]  [<ffffffff810ae8ff>] start_flush_work+0x2f/0x290
> > >> [   24.705789]  [<ffffffff810ae8ac>] flush_work+0x5c/0x80
> > >> [   24.705792]  [<ffffffff810ae86a>] ? flush_work+0x1a/0x80
> > >> [   24.705799]  [<ffffffff810eddcd>] ? trace_hardirqs_off+0xd/0x10
> > >> [   24.705804]  [<ffffffff810ad938>] ? try_to_grab_pending+0x48/0x360
> > >> [   24.705810]  [<ffffffff81917e13>] ? _raw_spin_lock_irqsave+0x73/0x80
> > >> [   24.705814]  [<ffffffff810aecf9>] __cancel_work_timer+0x179/0x260
> 
> This one is even more strange. It says that flush_work() is being called 
> from __cancel_work_timer() with IRQs disabled, but flags are explicitly 
> restored just one statement before that, and usbhid_close() explicitly 
> calls cancel_work_sync() after unconditionally enabling interrupts.
> 
> So I am not able to make any sense of either of the traces really.
> 
> Are you seeing this with the same .config with GCC-compiled kernel as 
> well?

Actually could you please provide disassembly of your 
__cancel_work_timer()?

One explanation would be LLVM not considering local_irq_restore() a 
compiler memory barrier, but I am pretty sure it'll expose much more 
breakage if that'd be the case.

-- 
Jiri Kosina
SUSE Labs
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