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Date: Tue, 17 Sep 2013 22:23:32 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
Ingo Molnar <mingo@...nel.org>
Cc: Andi Kleen <ak@...ux.intel.com>, Peter Anvin <hpa@...or.com>,
Mike Galbraith <bitbucket@...ine.de>,
Thomas Gleixner <tglx@...utronix.de>,
Arjan van de Ven <arjan@...ux.intel.com>,
Frederic Weisbecker <fweisbec@...il.com>,
linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 11/11] sched, x86: Optimize the preempt_schedule() call
Another build error by Thomas Meyer.. we need to export the asm symbols.
---
Subject: sched, x86: Optimize the preempt_schedule() call
From: Peter Zijlstra <peterz@...radead.org>
Date: Wed Aug 14 14:51:00 CEST 2013
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@...ux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
---
arch/x86/include/asm/calling.h | 50 +++++++++++++++++++++++++++++++++++++++
arch/x86/include/asm/preempt.h | 8 ++++++
arch/x86/kernel/Makefile | 2 +
arch/x86/kernel/i386_ksyms_32.c | 7 +++++
arch/x86/kernel/preempt.S | 25 +++++++++++++++++++
arch/x86/kernel/x8664_ksyms_64.c | 7 +++++
include/asm-generic/preempt.h | 10 +++++++
include/linux/preempt.h | 13 +++-------
8 files changed, 114 insertions(+), 8 deletions(-)
--- a/arch/x86/include/asm/calling.h
+++ b/arch/x86/include/asm/calling.h
@@ -48,6 +48,8 @@ For 32-bit we have the following convent
#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 @@ For 32-bit we have the following convent
.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 */
+
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -95,4 +95,12 @@ static __always_inline bool should_resch
return unlikely(!__this_cpu_read_4(__preempt_count));
}
+#ifdef CONFIG_PREEMPT
+#define __preempt_schedule() asm ("call ___preempt_schedule")
+
+#ifdef CONFIG_CONTEXT_TRACKING
+#define __preempt_schedule_context() asm ("call ___preempt_schedule_context")
+#endif
+#endif /* CONFIG_PREEMPT */
+
#endif /* __ASM_PREEMPT_H */
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -36,6 +36,8 @@ obj-y += tsc.o io_delay.o rtc.o
obj-y += pci-iommu_table.o
obj-y += resource.o
+obj-$(CONFIG_PREEMPT) += preempt.o
+
obj-y += process.o
obj-y += i387.o xsave.o
obj-y += ptrace.o
--- a/arch/x86/kernel/i386_ksyms_32.c
+++ b/arch/x86/kernel/i386_ksyms_32.c
@@ -37,3 +37,10 @@ EXPORT_SYMBOL(strstr);
EXPORT_SYMBOL(csum_partial);
EXPORT_SYMBOL(empty_zero_page);
+
+#ifdef CONFIG_PREEMPT
+EXPORT_SYMBOL(___preempt_schedule);
+#ifdef CONFIG_CONTEXT_TRACKING
+EXPORT_SYMBOL(___preempt_schedule_context);
+#endif
+#endif
--- /dev/null
+++ b/arch/x86/kernel/preempt.S
@@ -0,0 +1,25 @@
+
+#include <linux/linkage.h>
+#include <asm/dwarf2.h>
+#include <asm/asm.h>
+#include <asm/calling.h>
+
+ENTRY(___preempt_schedule)
+ CFI_STARTPROC
+ SAVE_ALL
+ call preempt_schedule
+ RESTORE_ALL
+ ret
+ CFI_ENDPROC
+
+#ifdef CONFIG_CONTEXT_TRACKING
+
+ENTRY(___preempt_schedule_context)
+ CFI_STARTPROC
+ SAVE_ALL
+ call preempt_schedule_context
+ RESTORE_ALL
+ ret
+ CFI_ENDPROC
+
+#endif
--- a/arch/x86/kernel/x8664_ksyms_64.c
+++ b/arch/x86/kernel/x8664_ksyms_64.c
@@ -66,3 +66,10 @@ EXPORT_SYMBOL(empty_zero_page);
#ifndef CONFIG_PARAVIRT
EXPORT_SYMBOL(native_load_gs_index);
#endif
+
+#ifdef CONFIG_PREEMPT
+EXPORT_SYMBOL(___preempt_schedule);
+#ifdef CONFIG_CONTEXT_TRACKING
+EXPORT_SYMBOL(___preempt_schedule_context);
+#endif
+#endif
--- a/include/asm-generic/preempt.h
+++ b/include/asm-generic/preempt.h
@@ -90,4 +90,14 @@ static __always_inline bool should_resch
return unlikely(!*preempt_count_ptr());
}
+#ifdef CONFIG_PREEMPT
+extern asmlinkage void preempt_schedule(void);
+#define __preempt_schedule() preempt_schedule()
+
+#ifdef CONFIG_CONTEXT_TRACKING
+extern asmlinkage void preempt_schedule_context(void);
+#define __preempt_schedule_context() preempt_schedule_context()
+#endif
+#endif /* CONFIG_PREEMPT */
+
#endif /* __ASM_PREEMPT_H */
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -50,18 +50,17 @@ do { \
#define preempt_enable_no_resched() sched_preempt_enable_no_resched()
#ifdef CONFIG_PREEMPT
-asmlinkage void preempt_schedule(void);
#define preempt_enable() \
do { \
barrier(); \
if (unlikely(preempt_count_dec_and_test())) \
- preempt_schedule(); \
+ __preempt_schedule(); \
} while (0)
#define preempt_check_resched() \
do { \
if (should_resched()) \
- preempt_schedule(); \
+ __preempt_schedule(); \
} while (0)
#else
@@ -83,17 +82,15 @@ do { \
#ifdef CONFIG_PREEMPT
-#ifdef CONFIG_CONTEXT_TRACKING
-asmlinkage void preempt_schedule_context(void);
-#else
-#define preempt_schedule_context() preempt_schedule()
+#ifndef CONFIG_CONTEXT_TRACKING
+#define __preempt_schedule_context() __preempt_schedule()
#endif
#define preempt_enable_notrace() \
do { \
barrier(); \
if (unlikely(__preempt_count_dec_and_test())) \
- preempt_schedule_context(); \
+ __preempt_schedule_context(); \
} while (0)
#else
#define preempt_enable_notrace() preempt_enable_no_resched_notrace()
--
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