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The call to pm_runtime_get_sync() in ufshcd_program_key() can deadlock
because it waits for the UFS controller to be resumed, but it can itself
be reached while resuming the UFS controller via:
- ufshcd_runtime_resume()
- ufshcd_resume()
- ufshcd_reset_and_restore()
- ufshcd_host_reset_and_restore()
- ufshcd_hba_enable()
- ufshcd_hba_execute_hce()
- ufshcd_hba_start()
- ufshcd_crypto_enable()
- keyslot_manager_reprogram_all_keys()
- ufshcd_crypto_keyslot_program()
- ufshcd_program_key()
But pm_runtime_get_sync() *is* needed when evicting a key. Also, on
pre-4.20 kernels it's needed when programming a keyslot for a bio since
the block layer used to resume the device in a different place.
Thus, it's hard for drivers to know what to do in .keyslot_program() and
.keyslot_evict(). In old kernels it may even be impossible unless we
were to pass more information down from the keyslot_manager.
There's also another possible deadlock: keyslot programming and eviction
take ksm->lock for write and then resume the device, which may result in
ksm->lock being taken again via the above call stack. To fix this, we
should resume the device before taking ksm->lock.
Fix these problems by moving to a better design where the block layer
(namely, the keyslot manager) handles runtime power management instead
of drivers. This is analogous to the block layer's existing runtime
power management support (blk-pm), which handles resuming devices when
bios are submitted to them so that drivers don't need to handle it.
Test: Tested on coral with:
echo 5 > /sys/bus/platform/devices/1d84000.ufshc/rpm_lvl
sleep 30
touch /data && sync # hangs before this fix
Also verified via kvm-xfstests that blk-crypto-fallback continues
to work both with and without CONFIG_PM=y.
Bug: 137270441
Bug: 149368295
Change-Id: I6bc9fb81854afe7edf490d71796ee68a61f7cbc8
Signed-off-by: Eric Biggers <ebiggers@google.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
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In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.