Date: Tue, 15 Mar 2011 18:46:29 +0000
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
        Saeed Bishara <saeed.bishara@gmail.com>,
        Jens Axboe <jens.axboe@oracle.com>
Subject: Re: [PATCH] Avoid indefinite wait in smp_call_function_many() if
	cpumask is modified
Message-ID: <20110315184629.GB3620@n2100.arm.linux.org.uk>
References: <20110315181941.26948.65323.stgit@e102109-lin.cambridge.arm.com>
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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.
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