linux-kernel - Re: latest -git: WARNING: at arch/x86/kernel/ipi.c:123 send_IPI_mask

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Message-ID: <48AFB1C2.5020806@zytor.com>
Date:	Fri, 22 Aug 2008 23:44:18 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Andi Kleen <andi@...stfloor.org>,
	"H. Peter Anvin" <hpa@...nel.org>, Dave Jones <davej@...hat.com>,
	Vegard Nossum <vegard.nossum@...il.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: latest -git: WARNING: at arch/x86/kernel/ipi.c:123	send_IPI_mask_bitmask+0xc3/0xe0()

Jeremy Fitzhardinge wrote:
> H. Peter Anvin wrote:
>> Well, smp_call_function_single already does all necessary locking; it
>> makes more sense for it to check that what it's about to call still
>> exists while inside the lock, instead of requiring the higher layers
>> to guarantee that cannot happen on it.  This is simply a matter of the
>> cost of checking at this point being quite low. 
> 
> It does, already doesn't it?  Hm, smp_call_function_mask() ands the
> provided mask with the online mask, but it doesn't look like
> smp_call_function_single() does the equivalent.

It doesn't, and that's how this bug was introduced.  It's a trivial add 
(see test patch already posted) and should hardly matter in terms of 
execution time.

I'll write up a clean patch with all the error propagation tomorrow or 
Sunday.

	-hpa
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