4.16-stable review patch. If anyone has any objections, please let me know.
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From: Yoshihiro Shimoda yoshihiro.shimoda.uh@renesas.com
[ Upstream commit 3e081628d510b2ddbe493371d9c574d9275da17e ]
This patch fixes an issue that a race condition happens between a client driver and the rcar-dmac driver:
- The rcar_dmac_isr_transfer_end() is called. - The done list appears, and desc.running is the next active list. - rcar_dmac_chan_get_residue() is called by a client driver before rcar_dmac_isr_channel_thread() is called. - The rcar_dmac_chan_get_residue() will not find any descriptors. - And, the following WARNING happens: WARN(1, "No descriptor for cookie!");
The sh-sci driver with HSCIF (921,600bps) on R-Car H3 can cause this situation. So, this patch checks the done lists in rcar_dmac_chan_get_residue() and returns zero if the done lists has the argument cookie.
Tested-by: Nguyen Viet Dung dung.nguyen.aj@renesas.com Signed-off-by: Yoshihiro Shimoda yoshihiro.shimoda.uh@renesas.com Signed-off-by: Vinod Koul vinod.koul@intel.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/dma/sh/rcar-dmac.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/drivers/dma/sh/rcar-dmac.c +++ b/drivers/dma/sh/rcar-dmac.c @@ -1301,8 +1301,17 @@ static unsigned int rcar_dmac_chan_get_r * If the cookie doesn't correspond to the currently running transfer * then the descriptor hasn't been processed yet, and the residue is * equal to the full descriptor size. + * Also, a client driver is possible to call this function before + * rcar_dmac_isr_channel_thread() runs. In this case, the "desc.running" + * will be the next descriptor, and the done list will appear. So, if + * the argument cookie matches the done list's cookie, we can assume + * the residue is zero. */ if (cookie != desc->async_tx.cookie) { + list_for_each_entry(desc, &chan->desc.done, node) { + if (cookie == desc->async_tx.cookie) + return 0; + } list_for_each_entry(desc, &chan->desc.pending, node) { if (cookie == desc->async_tx.cookie) return desc->size;