[PATCH] rapidio/tsi721: use tasklet_kill in device remove/release process

[PATCH] rapidio/tsi721: use tasklet_kill in device remove/release process

[Xiaotian Feng]

Some driver uses 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.

Signed-off-by: Xiaotian Feng <dannyfeng@tencent.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Andrew Morton <akpm@linux-foundation.org> 
---
 drivers/rapidio/devices/tsi721_dma.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/rapidio/devices/tsi721_dma.c b/drivers/rapidio/devices/tsi721_dma.c
index 92e06a5..a098fbc 100644
--- a/drivers/rapidio/devices/tsi721_dma.c
+++ b/drivers/rapidio/devices/tsi721_dma.c
@@ -589,7 +589,7 @@ static void tsi721_free_chan_resources(struct dma_chan *dchan)
 	BUG_ON(!list_empty(&bdma_chan->active_list));
 	BUG_ON(!list_empty(&bdma_chan->queue));
 
-	tasklet_disable(&bdma_chan->tasklet);
+	tasklet_kill(&bdma_chan->tasklet);
 
 	spin_lock_bh(&bdma_chan->lock);
 	list_splice_init(&bdma_chan->free_list, &list);
-- 
1.7.9.5

RE: [PATCH] rapidio/tsi721: use tasklet_kill in device remove/release process

[Bounine, Alexandre]

On Wed, October 31, 2012 6:53 AM
Xiaotian Feng <xtfeng@gmail.com> wrote:
> 
> Some driver uses 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.
> 
> Signed-off-by: Xiaotian Feng <dannyfeng@tencent.com>
> Cc: Matt Porter <mporter@kernel.crashing.org>
> Cc: Alexandre Bounine <alexandre.bounine@idt.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
>  drivers/rapidio/devices/tsi721_dma.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/rapidio/devices/tsi721_dma.c
> b/drivers/rapidio/devices/tsi721_dma.c
> index 92e06a5..a098fbc 100644
> --- a/drivers/rapidio/devices/tsi721_dma.c
> +++ b/drivers/rapidio/devices/tsi721_dma.c
> @@ -589,7 +589,7 @@ static void tsi721_free_chan_resources(struct
> dma_chan *dchan)
>  	BUG_ON(!list_empty(&bdma_chan->active_list));
>  	BUG_ON(!list_empty(&bdma_chan->queue));
> 
> -	tasklet_disable(&bdma_chan->tasklet);
> +	tasklet_kill(&bdma_chan->tasklet);
> 
>  	spin_lock_bh(&bdma_chan->lock);
>  	list_splice_init(&bdma_chan->free_list, &list);
> --
> 1.7.9.5

I agree with reported issue.
Switching to tasklet_kill() also requires to disable interrupts first.
I will update that part and post a new patch.