* [PATCH] arm64: kernel thread don't need to save fpsimd context.
@ 2015-06-11 4:04 Chunyan Zhang
2015-06-11 14:40 ` Catalin Marinas
0 siblings, 1 reply; 2+ messages in thread
From: Chunyan Zhang @ 2015-06-11 4:04 UTC (permalink / raw)
To: linux-arm-kernel
From: Janet Liu <janet.liu@spreadtrum.com>
kernel thread's default fpsimd state is zero. When fork a thread, if parent is kernel thread,
and save hardware context to parent's fpsimd state, but this hardware context is user
process's context, because kernel thread don't use fpsimd, it will not introduce issue,
it add a little cost.
Signed-off-by: Janet Liu <janet.liu@spreadtrum.com>
Signed-off-by: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
---
arch/arm64/kernel/process.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index c6b1f3b..2a46732 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -243,7 +243,8 @@ void release_thread(struct task_struct *dead_task)
int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
- fpsimd_preserve_current_state();
+ if (current->mm)
+ fpsimd_preserve_current_state();
*dst = *src;
return 0;
}
--
1.7.9.5
^ permalink raw reply related [flat|nested] 2+ messages in thread* [PATCH] arm64: kernel thread don't need to save fpsimd context.
2015-06-11 4:04 [PATCH] arm64: kernel thread don't need to save fpsimd context Chunyan Zhang
@ 2015-06-11 14:40 ` Catalin Marinas
0 siblings, 0 replies; 2+ messages in thread
From: Catalin Marinas @ 2015-06-11 14:40 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Jun 11, 2015 at 12:04:32PM +0800, Chunyan Zhang wrote:
> From: Janet Liu <janet.liu@spreadtrum.com>
>
> kernel thread's default fpsimd state is zero. When fork a thread, if parent is kernel thread,
> and save hardware context to parent's fpsimd state, but this hardware context is user
> process's context, because kernel thread don't use fpsimd, it will not introduce issue,
> it add a little cost.
>
> Signed-off-by: Janet Liu <janet.liu@spreadtrum.com>
> Signed-off-by: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
Applied. Thanks.
--
Catalin
^ permalink raw reply [flat|nested] 2+ messages in thread
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