linux-kernel - Re: [PATCH RT 3.18] ring-buffer: Mark irq_work as HARD

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Date:	Thu, 16 Apr 2015 17:33:23 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Jan Kiszka <jan.kiszka@...mens.com>,
	Steven Rostedt <rostedt@...dmis.org>
CC:	RT <linux-rt-users@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RT 3.18] ring-buffer: Mark irq_work as HARD_IRQ to prevent
 deadlocks

On 04/16/2015 05:29 PM, Jan Kiszka wrote:
> My patch is definitely not OK. It causes
> 
> [  380.372579] BUG: scheduling while atomic: trace-cmd/2149/0x00010004
> ...
> [  380.372604] Call Trace:
> [  380.372610]  <IRQ>  [<ffffffff81607694>] dump_stack+0x50/0x9f
> [  380.372613]  [<ffffffff8160413c>] __schedule_bug+0x59/0x69
> [  380.372615]  [<ffffffff8160a1d5>] __schedule+0x675/0x800
> [  380.372617]  [<ffffffff8160a394>] schedule+0x34/0xa0
> [  380.372619]  [<ffffffff8160bf7d>] rt_spin_lock_slowlock+0xcd/0x290
> [  380.372621]  [<ffffffff8160d8b5>] rt_spin_lock+0x25/0x30
> [  380.372623]  [<ffffffff8108fe39>] __wake_up+0x29/0x60

right. you must not take any sleeping locks in the hardirq context :)
This works for the no-hz-work thingy. It grabs raw locks and may cancel
one hrtimer which is marked irqsafe.

Sebastian
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