linux-kernel - Re: [PATCH 1/8] x86, mce: stop calling del_timer

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Message-ID: <4DFED0A4.1060002@jp.fujitsu.com>
Date:	Mon, 20 Jun 2011 13:46:28 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	Borislav Petkov <bp@...64.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Luck, Tony" <tony.luck@...el.com>
Subject: Re: [PATCH 1/8] x86, mce: stop calling del_timer_sync() from interrupt

(2011/06/17 22:56), Borislav Petkov wrote:
> On Fri, Jun 17, 2011 at 04:40:36AM -0400, Hidetoshi Seto wrote:
>> Function del_timer_sync() has WARN_ON(in_irq()) in it because
>> calling it from interrupt context can cause deadlock if it
>> interrupts the target timer running.
> 
> No need to explain the del_timer_sync() code here - just say that it's
> not allowed to call it from an IRQ context.
> 

I'd like to add "why not allowed" in brief too...
Anyway I'll update the patch description and make it short.

>> only few MCE geeks experience this warning on write.
> 
> MCE geeks ??? I wonder who those are :-)

I'm just joking ;-)

>> +/* Must not be called from interrupt where del_timer_sync() can deadlock */
>> +static void mce_timer_delete_all(void)
>> +{
>> +	int cpu;
>> +
>> +	for_each_online_cpu(cpu) {
>> +		if (mce_available(&per_cpu(cpu_info, cpu)))
>> +			del_timer_sync(&per_cpu(mce_timer, cpu));
>> +	}
>> +}
> 
> You're adding the mce_available(..) check just to remove it in the next
> patch. Since all those sysfs nodes are behind such a check, there's no
> need for it here too.

Maybe it would be better to change the order of patches to make
this fix after the removal of unnecessary mce_available().


Thanks,
H.Seto


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