arm64: preempt: Fix big-endian when checking preempt count in assembly
authorWill Deacon <will.deacon@arm.com>
Tue, 11 Dec 2018 13:41:32 +0000 (13:41 +0000)
committerWill Deacon <will.deacon@arm.com>
Tue, 11 Dec 2018 20:07:03 +0000 (20:07 +0000)
commit7faa313f05cad184e8b17750f0cbe5216ac6debb
treec876a0fc11afaf73fb876d4756cc34a338bf5fa9
parent732291c4fab8b790847aa572703c01ad483b14d0
arm64: preempt: Fix big-endian when checking preempt count in assembly

Commit 396244692232 ("arm64: preempt: Provide our own implementation of
asm/preempt.h") extended the preempt count field in struct thread_info
to 64 bits, so that it consists of a 32-bit count plus a 32-bit flag
indicating whether or not the current task needs rescheduling.

Whilst the asm-offsets definition of TSK_TI_PREEMPT was updated to point
to this new field, the assembly usage was left untouched meaning that a
32-bit load from TSK_TI_PREEMPT on a big-endian machine actually returns
the reschedule flag instead of the count.

Whilst we could fix this by pointing TSK_TI_PREEMPT at the count field,
we're actually better off reworking the two assembly users so that they
operate on the whole 64-bit value in favour of inspecting the thread
flags separately in order to determine whether a reschedule is needed.

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
arch/arm64/include/asm/assembler.h
arch/arm64/kernel/entry.S