lkml.org 
[lkml]   [2014]   [Sep]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 09/13] dmaengine: edma: check for echan->edesc => NULL in edma_dma_pause()
    Date
    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.

    Cc: vinod.koul@intel.com
    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    ---
    drivers/dma/edma.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c
    index 7b65633f495e..123f578d6dd3 100644
    --- a/drivers/dma/edma.c
    +++ b/drivers/dma/edma.c
    @@ -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);
    --
    2.1.0


    \
     
     \ /
      Last update: 2014-09-29 20:21    [W:4.582 / U:0.688 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site