From e82b0b3828451c1cd331d9f304c6078fcd43b62e Mon Sep 17 00:00:00 2001 From: Lukas Wunner Date: Thu, 8 Nov 2018 08:06:10 +0100 Subject: [PATCH] spi: bcm2835: Fix race on DMA termination MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit If a DMA transfer finishes orderly right when spi_transfer_one_message() determines that it has timed out, the callbacks bcm2835_spi_dma_done() and bcm2835_spi_handle_err() race to call dmaengine_terminate_all(), potentially leading to double termination. Prevent by atomically changing the dma_pending flag before calling dmaengine_terminate_all(). Signed-off-by: Lukas Wunner Fixes: 3ecd37edaa2a ("spi: bcm2835: enable dma modes for transfers meeting certain conditions") Cc: stable@vger.kernel.org # v4.2+ Cc: Mathias Duckeck Cc: Frank Pavlic Cc: Martin Sperl Cc: Noralf Trønnes Signed-off-by: Mark Brown --- drivers/spi/spi-bcm2835.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index 594e9712ecbc..774161bbcb2e 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -232,10 +232,9 @@ static void bcm2835_spi_dma_done(void *data) * is called the tx-dma must have finished - can't get to this * situation otherwise... */ - dmaengine_terminate_all(master->dma_tx); - - /* mark as no longer pending */ - bs->dma_pending = 0; + if (cmpxchg(&bs->dma_pending, true, false)) { + dmaengine_terminate_all(master->dma_tx); + } /* and mark as completed */; complete(&master->xfer_completion); @@ -617,10 +616,9 @@ static void bcm2835_spi_handle_err(struct spi_master *master, struct bcm2835_spi *bs = spi_master_get_devdata(master); /* if an error occurred and we have an active dma, then terminate */ - if (bs->dma_pending) { + if (cmpxchg(&bs->dma_pending, true, false)) { dmaengine_terminate_all(master->dma_tx); dmaengine_terminate_all(master->dma_rx); - bs->dma_pending = 0; } /* and reset */ bcm2835_spi_reset_hw(master); -- 2.11.0