[PATCH] rapidio/tsi721: fix tasklet termination in dma channel release

[Thomas Gleixner]

On Fri, 21 Feb 2014, Alexandre Bounine wrote:
> This patch is a modification of the patch originally proposed
> by Xiaotian Feng <xtfeng at gmail.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 at idt.com>
> Cc: Matt Porter <mporter at kernel.crashing.org>
> Cc: Xiaotian Feng <xtfeng at gmail.com>
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: Mike Galbraith <bitbucket at online.de>
> Cc: <stable at vger.kernel.org>

Reviewed-by: Thomas Gleixner <tglx at linutronix.de>