From: Will Deacon will.deacon@arm.com
[ Upstream commit 7faa313f05cad184e8b17750f0cbe5216ac6debb ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/include/asm/assembler.h | 8 +++----- arch/arm64/kernel/entry.S | 6 ++---- 2 files changed, 5 insertions(+), 9 deletions(-)
diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index 5a97ac8531682..0c100506a29aa 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -683,11 +683,9 @@ USER(\label, ic ivau, \tmp2) // invalidate I line PoU .macro if_will_cond_yield_neon #ifdef CONFIG_PREEMPT get_thread_info x0 - ldr w1, [x0, #TSK_TI_PREEMPT] - ldr x0, [x0, #TSK_TI_FLAGS] - cmp w1, #PREEMPT_DISABLE_OFFSET - csel x0, x0, xzr, eq - tbnz x0, #TIF_NEED_RESCHED, .Lyield_@ // needs rescheduling? + ldr x0, [x0, #TSK_TI_PREEMPT] + sub x0, x0, #PREEMPT_DISABLE_OFFSET + cbz x0, .Lyield_@ /* fall through to endif_yield_neon */ .subsection 1 .Lyield_@ : diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 5f800384cb9a8..bb68323530458 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -622,10 +622,8 @@ el1_irq: irq_handler
#ifdef CONFIG_PREEMPT - ldr w24, [tsk, #TSK_TI_PREEMPT] // get preempt count - cbnz w24, 1f // preempt count != 0 - ldr x0, [tsk, #TSK_TI_FLAGS] // get flags - tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling? + ldr x24, [tsk, #TSK_TI_PREEMPT] // get preempt count + cbnz x24, 1f // preempt count != 0 bl el1_preempt 1: #endif