linux-kernel - Re: [PATCH] lib/spinlock_debug: avoid one thread can not obtain the spinlock for a long time.

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Message-ID: <20140430074307.GX11096@twins.programming.kicks-ass.net>
Date:	Wed, 30 Apr 2014 09:43:07 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Wang, Xiaoming" <xiaoming.wang@...el.com>
Cc:	"mingo@...hat.com" <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Liu, Chuansheng" <chuansheng.liu@...el.com>
Subject: Re: [PATCH] lib/spinlock_debug: avoid one thread can not obtain the
 spinlock for a long time.

On Wed, Apr 30, 2014 at 06:17:48AM +0000, Wang, Xiaoming wrote:
> Dear Peter
> 	If we wait the end of loop as loops_per_jiffy. 
> It may last more than 130s and local IRQ disabled at interval 
> which may cause Hard LOCKUP. We break out in 1 second and
> dump the stack for debug.

Yeah, so? That makes shoddy engineering alright then?

So either fix the loops_per_jiffy thing, it is supposed to wait for 1
second after all, or explain why its broken and entirely replace it.

What you do not do is make a loop with 2 differently broken timeouts and
hope one works.
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