Commit-ID: fb14b4eadf73500d3b2104f031472a268562c047 Gitweb: http://git.kernel.org/tip/fb14b4eadf73500d3b2104f031472a268562c047 Author: Oleg Nesterov <[email protected]> AuthorDate: Wed, 11 Mar 2015 18:34:09 +0100 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 23 Mar 2015 10:13:58 +0100
x86/fpu: Document user_fpu_begin() Currently, user_fpu_begin() has a single caller and it is not clear why do we actually need it and why we should not worry about preemption right after preempt_enable(). Signed-off-by: Oleg Nesterov <[email protected]> Signed-off-by: Borislav Petkov <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Fenghua Yu <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Pekka Riikonen <[email protected]> Cc: Quentin Casasnovas <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Suresh Siddha <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/include/asm/fpu-internal.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h index 810f20f..c58c930 100644 --- a/arch/x86/include/asm/fpu-internal.h +++ b/arch/x86/include/asm/fpu-internal.h @@ -508,10 +508,12 @@ static inline int restore_xstate_sig(void __user *buf, int ia32_frame) } /* - * Need to be preemption-safe. + * Needs 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. + * the save state. It does not do any saving/restoring on its own. In + * lazy FPU mode, it is just an optimization to avoid a #NM exception, + * the task can lose the FPU right after preempt_enable(). */ static inline void user_fpu_begin(void) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
