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dmaengine: shdma: fix a race condition in __ld_cleanup()

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This patch fixes a race condition about a list of shdma-base driver.
If we don't apply this patch, a dma slave driver (especially a usb
peripheral driver) may not be able to start the transfer.

If a dma slave driver has a callback, __ld_cleanup() will call
the callback before this driver removes the list. After the callback,
since the return value of __ld_cleanup() is not zero,
shdma_chan_ld_cleanup() calls __ld_cleanup() again. And, __ld_clean()
will removes the list.

At this time, if a dma slave driver calls dmaengine_submit() before
this driver removes the list, this driver will set schan->pm_state
to SHDMA_PM_PENDING in shdma_tx_submit(). And then, even if a dma
slave driver calls dma_async_issue_pending(), this driver don't
start the transfer because the schan->pm_state is SHDMA_PM_PENDING
in shdma_issue_pending().

So, this patch adds a new condition in __ld_clean() to check if the
schan->pm_state is SHDMA_PM_PENDING or not.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
This commit is contained in:
Yoshihiro Shimoda 2014-10-09 11:09:00 +09:00 committed by Vinod Koul
parent ce9406380d
commit 26fd830a99
1 changed files with 2 additions and 0 deletions
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2
drivers/dma/sh/shdma-base.c
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@ -391,6 +391,8 @@ static dma_async_tx_callback __ld_cleanup(struct shdma_chan *schan, bool all)
dev_dbg(schan->dev, "Bring down channel %d\n", schan->id);
pm_runtime_put(schan->dev);
schan->pm_state = SHDMA_PM_ESTABLISHED;
} else if (schan->pm_state == SHDMA_PM_PENDING) {
shdma_chan_xfer_ld_queue(schan);
}
}
}