Commit 512255a2 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar

Revert "sched/x86_64: Don't save flags on context switch"

This reverts commit:

  2c7577a7 ("sched/x86_64: Don't save flags on context switch")

It was a nice speedup.  It's also not quite correct: SYSENTER
enables interrupts too early.

We can re-add this optimization once the SYSENTER code is beaten
into shape, which should happen in 4.3 or 4.4.
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org # v3.19
Link: http://lkml.kernel.org/r/85f56651f59f76624e80785a8fd3bdfdd089a818.1439838962.git.luto@kernel.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 2c6625cd
...@@ -79,12 +79,12 @@ do { \ ...@@ -79,12 +79,12 @@ do { \
#else /* CONFIG_X86_32 */ #else /* CONFIG_X86_32 */
/* frame pointer must be last for get_wchan */ /* frame pointer must be last for get_wchan */
#define SAVE_CONTEXT "pushq %%rbp ; movq %%rsi,%%rbp\n\t" #define SAVE_CONTEXT "pushf ; pushq %%rbp ; movq %%rsi,%%rbp\n\t"
#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp\t" #define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp ; popf\t"
#define __EXTRA_CLOBBER \ #define __EXTRA_CLOBBER \
, "rcx", "rbx", "rdx", "r8", "r9", "r10", "r11", \ , "rcx", "rbx", "rdx", "r8", "r9", "r10", "r11", \
"r12", "r13", "r14", "r15", "flags" "r12", "r13", "r14", "r15"
#ifdef CONFIG_CC_STACKPROTECTOR #ifdef CONFIG_CC_STACKPROTECTOR
#define __switch_canary \ #define __switch_canary \
...@@ -100,11 +100,7 @@ do { \ ...@@ -100,11 +100,7 @@ do { \
#define __switch_canary_iparam #define __switch_canary_iparam
#endif /* CC_STACKPROTECTOR */ #endif /* CC_STACKPROTECTOR */
/* /* Save restore flags to clear handle leaking NT */
* There is no need to save or restore flags, because flags are always
* clean in kernel mode, with the possible exception of IOPL. Kernel IOPL
* has no effect.
*/
#define switch_to(prev, next, last) \ #define switch_to(prev, next, last) \
asm volatile(SAVE_CONTEXT \ asm volatile(SAVE_CONTEXT \
"movq %%rsp,%P[threadrsp](%[prev])\n\t" /* save RSP */ \ "movq %%rsp,%P[threadrsp](%[prev])\n\t" /* save RSP */ \
......
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