linux-kernel - Re: workqueue deadlock

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Message-ID: <20061207064512.GA27583@in.ibm.com>
Date:	Thu, 7 Dec 2006 12:15:12 +0530
From:	Srivatsa Vaddagiri <vatsa@...ibm.com>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Myron Stowe <myron.stowe@...com>, Jens Axboe <axboe@...nel.dk>,
	Dipankar <dipankar@...ibm.com>, Andrew Morton <akpm@...l.org>,
	Gautham shenoy <ego@...ibm.com>
Subject: Re: workqueue deadlock

On Thu, Dec 07, 2006 at 11:47:01AM +0530, Srivatsa Vaddagiri wrote:
> 	- Make it rw-sem

I think rw-sems also were shown to hit deadlocks (recursive read-lock
attempt deadlocks when a writer comes between the two read attempts by the same
thread). So below suggestion only seems to makes sense ..

> 	- Make it per-cpu mutex, which could be either:
> 
> 		http://lkml.org/lkml/2006/11/30/110 - Ingo's suggestion
> 		http://lkml.org/lkml/2006/10/26/65 - Gautham's work based on RCU
> 
> In Ingo's suggestion, I really dont know if the task_struct
> modifications is a good thing (to support recursive requirements).
> Gautham's patches avoid modifications to task_struct, is fast but can
> starve writers (who want to bring down/up a CPU).

-- 
Regards,
vatsa
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