dmaengine: pl330: fix irq race with terminate_all

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>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 451370d..9e38947 100644 (file)
--- 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;