sched, x86: Optimize the preempt_schedule() call
Remove the bloat of the C calling convention out of the
preempt_enable() sites by creating an ASM wrapper which allows us to
do an asm("call ___preempt_schedule") instead.
calling.h bits by Andi Kleen
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-tk7xdi1cvvxewixzke8t8le1@git.kernel.org
[ Fixed build error. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/include/asm/calling.h b/arch/x86/include/asm/calling.h
index 0fa6750..cb4c73b 100644
--- a/arch/x86/include/asm/calling.h
+++ b/arch/x86/include/asm/calling.h
@@ -48,6 +48,8 @@
#include <asm/dwarf2.h>
+#ifdef CONFIG_X86_64
+
/*
* 64-bit system call stack frame layout defines and helpers,
* for assembly code:
@@ -192,3 +194,51 @@
.macro icebp
.byte 0xf1
.endm
+
+#else /* CONFIG_X86_64 */
+
+/*
+ * For 32bit only simplified versions of SAVE_ALL/RESTORE_ALL. These
+ * are different from the entry_32.S versions in not changing the segment
+ * registers. So only suitable for in kernel use, not when transitioning
+ * from or to user space. The resulting stack frame is not a standard
+ * pt_regs frame. The main use case is calling C code from assembler
+ * when all the registers need to be preserved.
+ */
+
+ .macro SAVE_ALL
+ pushl_cfi %eax
+ CFI_REL_OFFSET eax, 0
+ pushl_cfi %ebp
+ CFI_REL_OFFSET ebp, 0
+ pushl_cfi %edi
+ CFI_REL_OFFSET edi, 0
+ pushl_cfi %esi
+ CFI_REL_OFFSET esi, 0
+ pushl_cfi %edx
+ CFI_REL_OFFSET edx, 0
+ pushl_cfi %ecx
+ CFI_REL_OFFSET ecx, 0
+ pushl_cfi %ebx
+ CFI_REL_OFFSET ebx, 0
+ .endm
+
+ .macro RESTORE_ALL
+ popl_cfi %ebx
+ CFI_RESTORE ebx
+ popl_cfi %ecx
+ CFI_RESTORE ecx
+ popl_cfi %edx
+ CFI_RESTORE edx
+ popl_cfi %esi
+ CFI_RESTORE esi
+ popl_cfi %edi
+ CFI_RESTORE edi
+ popl_cfi %ebp
+ CFI_RESTORE ebp
+ popl_cfi %eax
+ CFI_RESTORE eax
+ .endm
+
+#endif /* CONFIG_X86_64 */
+