From 7106a5ab89c50c6b5aadea0850b40323804a922d Mon Sep 17 00:00:00 2001 From: Benjamin LaHaise Date: Sat, 10 Jan 2009 23:00:22 -0500 Subject: x86-64: remove locked instruction from switch_to() Impact: micro-optimization The patch below removes an unnecessary locked instruction from switch_to(). TIF_FORK is only ever set in copy_thread() on initial process creation, and gets cleared during the first scheduling of the process. As such, it is safe to use an unlocked test for the flag within switch_to(). Signed-off-by: Benjamin LaHaise Signed-off-by: Ingo Molnar --- arch/x86/kernel/entry_64.S | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/x86/kernel/entry_64.S') diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index e28c7a987793..38dd37458e44 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -408,6 +408,8 @@ END(save_paranoid) ENTRY(ret_from_fork) DEFAULT_FRAME + LOCK ; btr $TIF_FORK,TI_flags(%r8) + push kernel_eflags(%rip) CFI_ADJUST_CFA_OFFSET 8 popf # reset kernel eflags -- cgit v1.2.3