4.4-stable review patch. If anyone has any objections, please let me know.
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From: Leonid Iziumtsev leonid.iziumtsev@gmail.com
commit 341198eda723c8c1cddbb006a89ad9e362502ea2 upstream.
Once the "ld_queue" list is not empty, next descriptor will migrate into "ld_active" list. The "desc" variable will be overwritten during that transition. And later the dmaengine_desc_get_callback_invoke() will use it as an argument. As result we invoke wrong callback.
That behaviour was in place since: commit fcaaba6c7136 ("dmaengine: imx-dma: fix callback path in tasklet"). But after commit 4cd13c21b207 ("softirq: Let ksoftirqd do its job") things got worse, since possible delay between tasklet_schedule() from DMA irq handler and actual tasklet function execution got bigger. And that gave more time for new DMA request to be submitted and to be put into "ld_queue" list.
It has been noticed that DMA issue is causing problems for "mxc-mmc" driver. While stressing the system with heavy network traffic and writing/reading to/from sd card simultaneously the timeout may happen:
10013000.sdhci: mxcmci_watchdog: read time out (status = 0x30004900)
That often lead to file system corruption.
Signed-off-by: Leonid Iziumtsev leonid.iziumtsev@gmail.com Signed-off-by: Vinod Koul vkoul@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/dma/imx-dma.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
--- a/drivers/dma/imx-dma.c +++ b/drivers/dma/imx-dma.c @@ -619,7 +619,7 @@ static void imxdma_tasklet(unsigned long { struct imxdma_channel *imxdmac = (void *)data; struct imxdma_engine *imxdma = imxdmac->imxdma; - struct imxdma_desc *desc; + struct imxdma_desc *desc, *next_desc; unsigned long flags;
spin_lock_irqsave(&imxdma->lock, flags); @@ -649,10 +649,10 @@ static void imxdma_tasklet(unsigned long list_move_tail(imxdmac->ld_active.next, &imxdmac->ld_free);
if (!list_empty(&imxdmac->ld_queue)) { - desc = list_first_entry(&imxdmac->ld_queue, struct imxdma_desc, - node); + next_desc = list_first_entry(&imxdmac->ld_queue, + struct imxdma_desc, node); list_move_tail(imxdmac->ld_queue.next, &imxdmac->ld_active); - if (imxdma_xfer_desc(desc) < 0) + if (imxdma_xfer_desc(next_desc) < 0) dev_warn(imxdma->dev, "%s: channel: %d couldn't xfer desc\n", __func__, imxdmac->channel); }