linux-kernel - Re: [PATCH] hrtimer, softirq: Fix hrtimer->softirq trampoline

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Date:	Wed, 03 Feb 2010 09:47:38 +0800
From:	Wei Yongjun <yjwei@...fujitsu.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Yury Polyanskiy <ypolyans@...nceton.edu>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>, polyanskiy@...il.com,
	Thomas Gleixner <tglx@...utronix.de>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH]  hrtimer, softirq: Fix hrtimer->softirq trampoline

Peter Zijlstra wrote:
> On Tue, 2010-02-02 at 08:51 -0500, Yury Polyanskiy wrote:
>
> The original email had more information:
>
>   
>> {IN-HARDIRQ-W} state was registered at:
>>   [<c04718dc>] __lock_acquire+0xa9c/0x1890
>>   [<c047274f>] lock_acquire+0x7f/0xf0
>>   [<c0762958>] _raw_spin_lock+0x38/0x50
>>   [<c072b5ca>] xfrm_timer_handler+0x3a/0x260
>>   [<c0447d9d>] __hrtimer_tasklet_trampoline+0xd/0x10
>>   [<c04634ce>] hrtimer_run_queues+0x15e/0x2a0
>>   [<c045146d>] run_local_timers+0xd/0x20
>>   [<c04514b4>] update_process_times+0x34/0x70
>>   [<c046ce8a>] tick_periodic+0x2a/0x80
>>   [<c046cefe>] tick_handle_periodic+0x1e/0x90
>>   [<c0768377>] smp_apic_timer_interrupt+0x57/0x8b
>>   [<c076382f>] apic_timer_interrupt+0x2f/0x34
>>   [<c0401d3b>] cpu_idle+0x4b/0x80
>>   [<c074e0d7>] rest_init+0x67/0x70
>>   [<c0956874>] start_kernel+0x30e/0x314
>>   [<c095609e>] i386_start_kernel+0x9e/0xa5
>>     
>
> Which indicates we were called from hardirq context, it appears that
> that hrtimer_is_hres_active() case is indeed faulty. Not sure if I made
> a mistake when I wrote that or if we changed hrtimer behaviour
> afterwards, but the hrtimer fallback is still from hardirq context.
>
> Which would seem to suggest the following patch:
>
> ---
> Subject: hrtimer, softirq: Fix hrtimer->softirq trampoline
>
> hrtimers callbacks are always done from hardirq context, either the
> jiffy tick interrupt or the hrtimer device interrupt.
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>
>   

With this patch, the inconsistent lock state INFO is gone. Thanks.

Wei Yongjun

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