Commit 708f742e authored Nov 08, 2018 by Lukas Wunner Committed by Greg Kroah-Hartman Jan 09, 2019

spi: bcm2835: Fix race on DMA termination



commit e82b0b3828451c1cd331d9f304c6078fcd43b62e upstream.

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 <lukas@wunner.de>
Fixes: 3ecd37ed ("spi: bcm2835: enable dma modes for transfers meeting certain conditions")
Cc: stable@vger.kernel.org # v4.2+
Cc: Mathias Duckeck <m.duckeck@kunbus.de>
Cc: Frank Pavlic <f.pavlic@kunbus.de>
Cc: Martin Sperl <kernel@martin.sperl.org>
Cc: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 40a19e58

drivers/spi/spi-bcm2835.c

+4 −6

Original line number	Diff line number	Diff line
		@@ -233,10 +233,9 @@ static void bcm2835_spi_dma_done(void *data)
		* is called the tx-dma must have finished - can't get to this
		* situation otherwise...
		*/
		if (cmpxchg(&bs->dma_pending, true, false)) {
		dmaengine_terminate_all(master->dma_tx);

		/* mark as no longer pending */
		bs->dma_pending = 0;
		}

		/* 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);