Potential deadlock BUG in Linux 4.9 drivers/dma/coh901318.c
iago.abal at gmail.com
Fri Nov 18 01:49:03 PST 2016
With the help of a static bug finder (EBA -
https://github.com/models-team/eba) I have found a potential deadlock
in drivers/dma/coh901318.c. This happens due to a recursive
spin_lock_irqsave on `cohc->lock'.
This bug may have been introduced by commit 84c8447c544b ("DMAENGINE:
COH 901 318 fix bytesleft").
The fix seems easy, I would personally just remove the calls to
spin_(un)lock_irqsave in lines 1805 and 1826. Function
`coh901318_config' is only called by `coh901318_alloc_chan_resources'
which already holds that lock when calling it.
If someone can confirm that all the above is correct, I will be happy
to submit a patch.
The trace is as follows:
1. Function `coh901318_alloc_chan_resources' takes the lock first in line 2165:
// see https://github.com/torvalds/linux/blob/master/drivers/dma/coh901318.c#L2165
2. Immediately after it calls `coh901318_config' passing the `cohc'
struct to it.
3. The first thing `coh901318_config' does is to take the same
spinlock in line 1805:
// see https://github.com/torvalds/linux/blob/master/drivers/dma/coh901318.c#L1805
Hope it helps!
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