[PATCH] dmaengine: pl330: fix irq race with terminate_all

[PATCH] dmaengine: pl330: fix irq race with terminate_all

[John Keeping]

In pl330_update() when checking if a channel has been aborted, the
channel's lock is not taken, only the overall pl330_dmac lock.  But in
pl330_terminate_all() the aborted flag (req_running==-1) is set under
the channel lock and not the pl330_dmac lock.

With threaded interrupts, this leads to a potential race:

    pl330_terminate_all	        pl330_update
    -------------------         ------------
    lock channel
                                entry
    lock pl330
    _stop channel
    unlock pl330
                                lock pl330
                                check req_running != -1
    req_running = -1
                                _start channel

Signed-off-by: John Keeping <john@metanate.com>
---
 drivers/dma/pl330.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 370df2e74ddd..88750a34e859 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -2256,13 +2256,14 @@ static int pl330_terminate_all(struct dma_chan *chan)
 
 	pm_runtime_get_sync(pl330->ddma.dev);
 	spin_lock_irqsave(&pch->lock, flags);
+
 	spin_lock(&pl330->lock);
 	_stop(pch->thread);
-	spin_unlock(&pl330->lock);
-
 	pch->thread->req[0].desc = NULL;
 	pch->thread->req[1].desc = NULL;
 	pch->thread->req_running = -1;
+	spin_unlock(&pl330->lock);
+
 	power_down = pch->active;
 	pch->active = false;
 
-- 
2.18.0

Re: [PATCH] dmaengine: pl330: fix irq race with terminate_all

[Vinod]

On 17-07-18, 11:48, John Keeping wrote:
> In pl330_update() when checking if a channel has been aborted, the
> channel's lock is not taken, only the overall pl330_dmac lock.  But in
> pl330_terminate_all() the aborted flag (req_running==-1) is set under
> the channel lock and not the pl330_dmac lock.
> 
> With threaded interrupts, this leads to a potential race:
> 
>     pl330_terminate_all	        pl330_update
>     -------------------         ------------
>     lock channel
>                                 entry
>     lock pl330
>     _stop channel
>     unlock pl330
>                                 lock pl330
>                                 check req_running != -1
>     req_running = -1
>                                 _start channel
> 

Applied, thanks

-- 
~Vinod