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| author | Jon Hunter <jonathanh@nvidia.com> | 2016-03-08 12:28:20 +0000 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2016-03-09 09:31:39 +0700 |
| commit | 49023d2e4ead0fc9e0896331037746b267d46ad4 (patch) | |
| tree | 4550038559a27f6698a6702b3ee20c833a669f7c /Documentation | |
| parent | 628269704f19fcfc765499b7158effccfc79b6cf (diff) | |
spi: core: Fix deadlock when sending messages
The function __spi_pump_messages() is called by spi_pump_messages() and
__spi_sync(). The function __spi_sync() has an argument 'bus_locked'
that indicates if it is called with the SPI bus mutex held or not. If
'bus_locked' is false then __spi_sync() will acquire the mutex itself.
Commit 556351f14e74 ("spi: introduce accelerated read support for spi
flash devices") made a change to acquire the SPI bus mutex within
__spi_pump_messages(). However, this change did not check to see if the
mutex is already held. If __spi_sync() is called with the mutex held
(ie. 'bus_locked' is true), then a deadlock occurs when
__spi_pump_messages() is called.
Fix this deadlock by passing the 'bus_locked' state from __spi_sync() to
__spi_pump_messages() and only acquire the mutex if not already held. In
the case where __spi_pump_messages() is called from spi_pump_messages()
it is assumed that the mutex is not held and so call
__spi_pump_messages() with 'bus_locked' set to false. Finally, move the
unlocking of the mutex to the end of the __spi_pump_messages() function
to simplify the code and only call cond_resched() if there are no
errors.
Fixes: 556351f14e74 ("spi: introduce accelerated read support for spi flash devices")
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'Documentation')