linux-kernel - Re: contention on long-held spinlock

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Message-ID: <m27h69htdd.fsf@firstfloor.org>
Date:	Fri, 19 Aug 2011 16:30:22 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	Ortwin Glück <odi@....ch>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: contention on long-held spinlock

Ortwin Glück <odi@....ch> writes:
>
> I wonder if spinlocks could be made aware of such a situation and
> relax. Something like if spinning for more than 1000 times, perform a
> simple backoff and sleep. A spinlock should never spin busy for
> several seconds, right?

Spining for several seconds is always a bug. There's no way to make
this work. Please post backtraces (e.g. from perf record -g ; perf
report) and cc the driver maintainer, so that they can fix their
buggy code.

-Andi


-- 
ak@...ux.intel.com -- Speaking for myself only
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