Commit a40235a2 authored Aug 23, 2016 by Hsin-Yu Chao Committed by Vinod Koul Sep 09, 2016

dmaengine: pl330: Acquire dmac's spinlock in pl330_tx_status



There is a racing when accessing dmac thread in pl330_tx_status that
the pl330_update is handling active request at the same time and
changing the status of descriptors. This could cause an invalid
transferred count from BUSY descriptor added up to the residual number.
Fix the bug by using the dmac's spinlock in pl330_tx_status to protect
thread resources from changing.
Note that the nested order of holding dmac's and dma_chan's spinlock is
consistent with the rest of the driver: dma_chan first and then dmac,
so it is safe from deadlock scenario.

Signed-off-by: Hsin-Yu Chao <hychao@chromium.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

parent d64e9a2c

drivers/dma/pl330.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -2287,6 +2287,7 @@ pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
		goto out;

		spin_lock_irqsave(&pch->lock, flags);
		spin_lock(&pch->thread->dmac->lock);

		if (pch->thread->req_running != -1)
		running = pch->thread->req[pch->thread->req_running].desc;
		@@ -2329,6 +2330,7 @@ pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
		if (desc->last)
		residual = 0;
		}
		spin_unlock(&pch->thread->dmac->lock);
		spin_unlock_irqrestore(&pch->lock, flags);

		out:

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