diff options
| author | Ard Biesheuvel <ardb@kernel.org> | 2024-01-11 12:24:48 +0100 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2024-01-12 12:48:27 +0000 |
| commit | 3931261ecf46151a5e779c96fb3da00677b6dc37 (patch) | |
| tree | a66aef908d4546b826c5f63fe461283f0018932a /arch/arm64 | |
| parent | 8c5a19cb17a71e52303150335b459c7d2d28a155 (diff) | |
arm64: fpsimd: Bring cond_yield asm macro in line with new rules
We no longer disable softirqs or preemption when doing kernel mode SIMD,
and so for fully preemptible kernels, there is no longer a need to do any
explicit yielding (and for non-preemptible kernels, yielding is not
needed either).
That leaves voluntary preemption, where only explicit yield calls may
result in a reschedule. To retain the existing behavior for such a
configuration, we should take the new situation into account, where the
preempt count will be zero rather than one, and yielding to pending
softirqs is unnecessary.
Fixes: aefbab8e77eb ("arm64: fpsimd: Preserve/restore kernel mode NEON at context switch")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20240111112447.577640-2-ardb+git@google.com
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64')
| -rw-r--r-- | arch/arm64/include/asm/assembler.h | 25 | ||||
| -rw-r--r-- | arch/arm64/kernel/asm-offsets.c | 2 |
2 files changed, 9 insertions, 18 deletions
diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index 7b1975bf4b90..513787e43329 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -760,32 +760,25 @@ alternative_endif .endm /* - * Check whether preempt/bh-disabled asm code should yield as soon as - * it is able. This is the case if we are currently running in task - * context, and either a softirq is pending, or the TIF_NEED_RESCHED - * flag is set and re-enabling preemption a single time would result in - * a preempt count of zero. (Note that the TIF_NEED_RESCHED flag is - * stored negated in the top word of the thread_info::preempt_count + * Check whether asm code should yield as soon as it is able. This is + * the case if we are currently running in task context, and the + * TIF_NEED_RESCHED flag is set. (Note that the TIF_NEED_RESCHED flag + * is stored negated in the top word of the thread_info::preempt_count * field) */ - .macro cond_yield, lbl:req, tmp:req, tmp2:req + .macro cond_yield, lbl:req, tmp:req, tmp2 +#ifdef CONFIG_PREEMPT_VOLUNTARY get_current_task \tmp ldr \tmp, [\tmp, #TSK_TI_PREEMPT] /* * If we are serving a softirq, there is no point in yielding: the * softirq will not be preempted no matter what we do, so we should - * run to completion as quickly as we can. + * run to completion as quickly as we can. The preempt_count field will + * have BIT(SOFTIRQ_SHIFT) set in this case, so the zero check will + * catch this case too. */ - tbnz \tmp, #SOFTIRQ_SHIFT, .Lnoyield_\@ -#ifdef CONFIG_PREEMPTION - sub \tmp, \tmp, #PREEMPT_DISABLE_OFFSET cbz \tmp, \lbl #endif - adr_l \tmp, irq_stat + IRQ_CPUSTAT_SOFTIRQ_PENDING - get_this_cpu_offset \tmp2 - ldr w\tmp, [\tmp, \tmp2] - cbnz w\tmp, \lbl // yield on pending softirq in task context -.Lnoyield_\@: .endm /* diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index 5ff1942b04fc..5a7dbbe0ce63 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -117,8 +117,6 @@ int main(void) DEFINE(DMA_FROM_DEVICE, DMA_FROM_DEVICE); BLANK(); DEFINE(PREEMPT_DISABLE_OFFSET, PREEMPT_DISABLE_OFFSET); - DEFINE(SOFTIRQ_SHIFT, SOFTIRQ_SHIFT); - DEFINE(IRQ_CPUSTAT_SOFTIRQ_PENDING, offsetof(irq_cpustat_t, __softirq_pending)); BLANK(); DEFINE(CPU_BOOT_TASK, offsetof(struct secondary_data, task)); BLANK(); |