Viacheslav Mitrofanov 5ab2782c94 dmaengine: sf-pdma: Add multithread support for a DMA channel ... [ Upstream commit b2cc5c465c ] When we get a DMA channel and try to use it in multiple threads it will cause oops and hanging the system. % echo 64 > /sys/module/dmatest/parameters/threads_per_chan % echo 10000 > /sys/module/dmatest/parameters/iterations % echo 1 > /sys/module/dmatest/parameters/run [ 89.480664] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000a0 [ 89.488725] Oops [#1] [ 89.494708] CPU: 2 PID: 1008 Comm: dma0chan0-copy0 Not tainted 5.17.0-rc5 [ 89.509385] epc : vchan_find_desc+0x32/0x46 [ 89.513553] ra : sf_pdma_tx_status+0xca/0xd6 This happens because of data race. Each thread rewrite channels's descriptor as soon as device_prep_dma_memcpy() is called. It leads to the situation when the driver thinks that it uses right descriptor that actually is freed or substituted for other one. With current fixes a descriptor changes its value only when it has been used. A new descriptor is acquired from vc->desc_issued queue that is already filled with descriptors that are ready to be sent. Threads have no direct access to DMA channel descriptor. Now it is just possible to queue a descriptor for further processing. Fixes: 6973886ad5 ("dmaengine: sf-pdma: add platform DMA support for HiFive Unleashed A00") Signed-off-by: Viacheslav Mitrofanov <v.v.mitrofanov@yadro.com> Link: https://lore.kernel.org/r/20220701082942.12835-1-v.v.mitrofanov@yadro.com Signed-off-by: Vinod Koul <vkoul@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2022-08-17 14:23:49 +02:00
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Kconfig	dmaengine: SF_PDMA depends on HAS_IOMEM	2021-05-31 09:44:14 +05:30
Makefile
sf-pdma.c	dmaengine: sf-pdma: Add multithread support for a DMA channel	2022-08-17 14:23:49 +02:00
sf-pdma.h	dmaengine: sf-pdma: move macro to header file	2019-11-22 11:15:28 +05:30