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dmaengine: edma: check for echan->edesc => NULL in edma_dma_pause()

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I added book keeping of whether or not the 8250-dma driver has an RX
transfer pending or not so we don't BUG here if it calls
dmaengine_pause() on a channel which has not a pending transfer. Guess
what, this is not enough.
The following can be triggered with a busy RX channel and hackbench in
background:
- DMA transfer completes. The callback is delayed via
  vchan_cookie_complete() into a tasklet so it das not happen asap.
- hackbench keeps the system busy so the tasklet does not run "soon".
- the UART collected enough data and generates an "timeout"-interrupt.
  Since 8250-dma *thinks* the DMA-transfer is still pending it tries to
  cancel it via invoking dmaengine_pause() first. This causes the segfault
  because echan->edesc is NULL now that the transfer completed (however
  the callback did not run yet).

With this patch we don't BUG in the scenario described.

Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Acked-by: Peter Ujfalusi <[email protected]>
Signed-off-by: Vinod Koul <[email protected]>
This commit is contained in:
Sebastian Andrzej Siewior 2014-09-29 20:06:45 +02:00 • committed by Vinod Koul
commit 639559ada6
1 changed files with 1 additions and 1 deletions
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2
drivers/dma/edma.c
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@ -288,7 +288,7 @@ static int edma_slave_config(struct edma_chan *echan,
static int edma_dma_pause(struct edma_chan *echan)
{
/* Pause/Resume only allowed with cyclic mode */
if (!echan->edesc->cyclic)
if (!echan->edesc || !echan->edesc->cyclic)
return -EINVAL;
edma_pause(echan->ch_num);