linux-kernel - Re: [PATCH] Avoid indefinite wait in smp_call_function

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Message-ID: <AANLkTinb52LL8rAM6A1SKrnz+Q=azc_9fQtiR7aYi+HW@mail.gmail.com>
Date:	Tue, 15 Mar 2011 22:36:55 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Catalin Marinas <catalin.marinas@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Saeed Bishara <saeed.bishara@...il.com>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [PATCH] Avoid indefinite wait in smp_call_function_many() if
 cpumask is modified

On Tuesday, 15 March 2011, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Tue, Mar 15, 2011 at 06:20:56PM +0000, Catalin Marinas wrote:
>> On ARM processors (and not only) with software broadcasting of the TLB
>> maintenance operations, smp_call_function_many() is given a
>> mm_cpumask(mm) as argument. This cpumask may be modified (bits cleared)
>> during the smp_call_function_many() execution as a result of other
>> events like ASID roll-over.
>
> We shouldn't be modifying a mask which has been passed into one of these
> functions.  Having masks change beneath a function which is actively
> using it and can wait is an obvious recipe for problems and races.

It's not that bad since the mask is copied inside the function.
Anyway, it looks like such patch has been around for more than a
month, so I'm not pushing it anymore.

Catalin

-- 
Catalin
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