linux-kernel - Re: [RFC] sched: make callers check lock contention for cond_resched

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Message-ID: <1336048150.22523.17.camel@twins>
Date:	Thu, 03 May 2012 14:29:10 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Takuya Yoshikawa <takuya.yoshikawa@...il.com>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, kvm@...r.kernel.org, avi@...hat.com,
	mtosatti@...hat.com, yoshikawa.takuya@....ntt.co.jp
Subject: Re: [RFC] sched: make callers check lock contention for
 cond_resched_lock()

On Thu, 2012-05-03 at 21:22 +0900, Takuya Yoshikawa wrote:
> Although the real use case is out of this RFC patch, we are now discussing
> a case in which we may hold a spin_lock for long time, ms order, depending
> on workload;  and in that case, other threads -- VCPU threads -- should be
> given higher priority for that problematic lock. 

Firstly, if you can hold a lock that long, it shouldn't be a spinlock,
secondly why isn't TIF_RESCHED being set if its running that long? That
should still make cond_resched_lock() break.
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