linux-kernel - Re: [PATCH] rapidio/tsi721: fix tasklet termination in dma channel release

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Date:	Fri, 21 Feb 2014 20:51:59 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Alexandre Bounine <alexandre.bounine@....com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	Matt Porter <mporter@...nel.crashing.org>,
	Xiaotian Feng <xtfeng@...il.com>,
	Mike Galbraith <bitbucket@...ine.de>, stable@...r.kernel.org
Subject: Re: [PATCH] rapidio/tsi721: fix tasklet termination in dma channel
 release

On Fri, 21 Feb 2014, Alexandre Bounine wrote:
> This patch is a modification of the patch originally proposed
> by Xiaotian Feng <xtfeng@...il.com>: https://lkml.org/lkml/2012/11/5/413
> This new version disables DMA channel interrupts and ensures that the tasklet
> wil not be scheduled again before calling tasklet_kill().
> 
> Unfortunately the updated patch was not released at that time due to planned
> rework of Tsi721 mport driver to use threaded interrupts (which has yet to
> happen).
> Recently the issue was reported again: https://lkml.org/lkml/2014/2/19/762.
> 
> Description from the original Xiaotian's patch:
> 
> "Some drivers use tasklet_disable in device remove/release process, 
> tasklet_disable will inc tasklet->count and return. If the tasklet is 
> not handled yet under some softirq pressure, the tasklet will be 
> placed on the tasklet_vec, never have a chance to be excuted. This 
> might lead to a heavy loaded ksoftirqd, wakeup with pending_softirq, 
> but tasklet is disabled. tasklet_kill should be used in this case."
> 
> This patch is applicable to kernel versions starting from v3.5.
> 
> Signed-off-by: Alexandre Bounine <alexandre.bounine@....com>
> Cc: Matt Porter <mporter@...nel.crashing.org>
> Cc: Xiaotian Feng <xtfeng@...il.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Mike Galbraith <bitbucket@...ine.de>
> Cc: <stable@...r.kernel.org>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
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