| Message ID | 20190814104131.20190-6-mark.rutland@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | kthread detection cleanup | expand |
On Wed, Aug 14, 2019 at 11:41:27AM +0100, Mark Rutland wrote: > Since commit: > > 6eb6c80187c55b7f ("arm64: kernel thread don't need to save fpsimd context.") > > ... we skip saving the fpsimd state for kernel threads in > arch_dup_task_struct(). We determine whether current is a kthread by > looking at current->mm. > > In general, a non-NULL current->mm doesn't imply that current is a > kthread, as kthreads can install an mm via use_mm(), and so it's > preferable to use is_kthread() to determine whether a thread is a > kthread. > > For consistency, let's use is_kthread() here. > > Signed-off-by: Mark Rutland <mark.rutland@arm.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Will Deacon <will@kernel.org> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 288012687c29..82b0a7a257cd 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -335,7 +335,7 @@ void arch_release_task_struct(struct task_struct *tsk) */ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) { - if (current->mm) + if (!is_kthread(current)) fpsimd_preserve_current_state(); *dst = *src;
Since commit: 6eb6c80187c55b7f ("arm64: kernel thread don't need to save fpsimd context.") ... we skip saving the fpsimd state for kernel threads in arch_dup_task_struct(). We determine whether current is a kthread by looking at current->mm. In general, a non-NULL current->mm doesn't imply that current is a kthread, as kthreads can install an mm via use_mm(), and so it's preferable to use is_kthread() to determine whether a thread is a kthread. For consistency, let's use is_kthread() here. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will@kernel.org> --- arch/arm64/kernel/process.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.11.0