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

From: John Keeping
Date: Tue Jul 17 2018 - 06:48:17 EST


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@xxxxxxxxxxxx>
---
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