| Date | Wed, 11 Mar 2015 18:34:09 +0100 | From | Oleg Nesterov <> | Subject | [PATCH 1/4] x86/fpu: document user_fpu_begin() |
| |
Currently user_fpu_begin() has a single caller and it is not clear that why do we actually need it, and why we should not worry about preemption right after preempt_enable().
Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- arch/x86/include/asm/fpu-internal.h | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h index 4bec98f..c615ae9 100644 --- a/arch/x86/include/asm/fpu-internal.h +++ b/arch/x86/include/asm/fpu-internal.h @@ -464,7 +464,9 @@ static inline int restore_xstate_sig(void __user *buf, int ia32_frame) * Need to be preemption-safe. * * NOTE! user_fpu_begin() must be used only immediately before restoring - * it. This function does not do any save/restore on their own. + * it. This function does not do any save/restore on its own. In a lazy + * fpu mode this is just optimization to avoid a dna fault, the task can + * lose FPU right after preempt_enable(). */ static inline void user_fpu_begin(void) { -- 1.5.5.1
|