diff options
author | Viacheslav Mitrofanov <v.v.mitrofanov@yadro.com> | 2022-07-01 11:29:42 +0300 |
---|---|---|
committer | Vinod Koul <vkoul@kernel.org> | 2022-07-06 18:10:34 +0530 |
commit | b2cc5c465c2cb8ab697c3fd6583c614e3f6cfbcc (patch) | |
tree | d1a9c40c70563896477ab3c3631cd9f7876d2e53 /drivers/most | |
parent | 4ce653d7c651d6a9fc6d5db4275624ac8d856b99 (diff) |
dmaengine: sf-pdma: Add multithread support for a DMA channel
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: 6973886ad58e ("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>
Diffstat (limited to 'drivers/most')
0 files changed, 0 insertions, 0 deletions