[RFC PATCH 2/5] irq_work: Only run irq_work from tick if arch needs it

[Frederic Weisbecker]

It may optimize a bit the tick path for archs that have their
own way to run irq work.

This may be further optimized using static keys.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 arch/alpha/include/asm/irq_work.h   |    5 ++++-
 arch/alpha/kernel/time.c            |    2 +-
 arch/powerpc/include/asm/irq_work.h |    4 +++-
 arch/powerpc/kernel/time.c          |    2 +-
 arch/sparc/include/asm/irq_work.h   |    4 +++-
 arch/sparc/kernel/pcr.c             |    2 +-
 arch/x86/include/asm/irq_work.h     |    9 +++++----
 arch/x86/kernel/irq_work.c          |    2 +-
 include/asm-generic/irq_work.h      |   13 +++++++++++++
 kernel/timer.c                      |    2 +-
 10 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/arch/alpha/include/asm/irq_work.h b/arch/alpha/include/asm/irq_work.h
index 814ff3d..3d32132 100644
--- a/arch/alpha/include/asm/irq_work.h
+++ b/arch/alpha/include/asm/irq_work.h
@@ -1,6 +1,9 @@
 #ifndef _ALPHA_IRQ_WORK_H
 #define _ALPHA_IRQ_WORK_H
 
-extern void arch_irq_work_raise(void);
+extern void __arch_irq_work_raise(void);
+#define arch_irq_work_raise __arch_irq_work_raise
+
+#include <asm-generic/irq_work.h>
 
 #endif
diff --git a/arch/alpha/kernel/time.c b/arch/alpha/kernel/time.c
index e336694..91c5eec 100644
--- a/arch/alpha/kernel/time.c
+++ b/arch/alpha/kernel/time.c
@@ -90,7 +90,7 @@ DEFINE_PER_CPU(u8, irq_work_pending);
 #define test_irq_work_pending()      __get_cpu_var(irq_work_pending)
 #define clear_irq_work_pending()     __get_cpu_var(irq_work_pending) = 0
 
-void arch_irq_work_raise(void)
+void __arch_irq_work_raise(void)
 {
 	set_irq_work_pending_flag();
 }
diff --git a/arch/powerpc/include/asm/irq_work.h b/arch/powerpc/include/asm/irq_work.h
index 8b9927f..8aa36aa 100644
--- a/arch/powerpc/include/asm/irq_work.h
+++ b/arch/powerpc/include/asm/irq_work.h
@@ -1,6 +1,8 @@
 #ifndef _ASM_POWERPC_IRQ_WORK_H
 #define _ASM_POWERPC_IRQ_WORK_H
 
-extern void arch_irq_work_raise(void);
+extern void __arch_irq_work_raise(void);
+#define arch_irq_work_raise __arch_irq_work_raise
 
+#include <asm-generic/irq_work.h>
 #endif
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index c9986fd..31565ac 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -466,7 +466,7 @@ DEFINE_PER_CPU(u8, irq_work_pending);
 
 #endif /* 32 vs 64 bit */
 
-void arch_irq_work_raise(void)
+void __arch_irq_work_raise(void)
 {
 	preempt_disable();
 	set_irq_work_pending_flag();
diff --git a/arch/sparc/include/asm/irq_work.h b/arch/sparc/include/asm/irq_work.h
index 1d062a6..383772d 100644
--- a/arch/sparc/include/asm/irq_work.h
+++ b/arch/sparc/include/asm/irq_work.h
@@ -1,6 +1,8 @@
 #ifndef ___ASM_SPARC_IRQ_H
 #define ___ASM_SPARC_IRQ_H
 
-extern void arch_irq_work_raise(void);
+extern void __arch_irq_work_raise(void);
+#define arch_irq_work_raise __arch_irq_work_raise
 
+#include <asm-generic/irq_work.h>
 #endif
diff --git a/arch/sparc/kernel/pcr.c b/arch/sparc/kernel/pcr.c
index 269af58..d1e1ecf 100644
--- a/arch/sparc/kernel/pcr.c
+++ b/arch/sparc/kernel/pcr.c
@@ -43,7 +43,7 @@ void __irq_entry deferred_pcr_work_irq(int irq, struct pt_regs *regs)
 	set_irq_regs(old_regs);
 }
 
-void arch_irq_work_raise(void)
+void __arch_irq_work_raise(void)
 {
 	set_softint(1 << PIL_DEFERRED_PCR_WORK);
 }
diff --git a/arch/x86/include/asm/irq_work.h b/arch/x86/include/asm/irq_work.h
index 38eed96..dad8266 100644
--- a/arch/x86/include/asm/irq_work.h
+++ b/arch/x86/include/asm/irq_work.h
@@ -1,10 +1,11 @@
 #ifndef _ASM_X86_IRQ_WORK_H
 #define _ASM_X86_IRQ_WORK_H
 
-#ifndef CONFIG_X86_LOCAL_APIC
-#include <asm-generic/irq_work.h>
-# else
-extern void arch_irq_work_raise(void);
+#ifdef CONFIG_X86_LOCAL_APIC
+extern void __arch_irq_work_raise(void);
+#define arch_irq_work_raise __arch_irq_work_raise
 #endif
 
+#include <asm-generic/irq_work.h>
+
 #endif
diff --git a/arch/x86/kernel/irq_work.c b/arch/x86/kernel/irq_work.c
index 95f5d4e..7389d5e 100644
--- a/arch/x86/kernel/irq_work.c
+++ b/arch/x86/kernel/irq_work.c
@@ -19,7 +19,7 @@ void smp_irq_work_interrupt(struct pt_regs *regs)
 }
 
 #ifdef CONFIG_X86_LOCAL_APIC
-void arch_irq_work_raise(void)
+void __arch_irq_work_raise(void)
 {
 	if (!cpu_has_apic)
 		return;
diff --git a/include/asm-generic/irq_work.h b/include/asm-generic/irq_work.h
index a2d4108..b172da0 100644
--- a/include/asm-generic/irq_work.h
+++ b/include/asm-generic/irq_work.h
@@ -4,6 +4,19 @@
 /*
  * Lame architectures will get the timer tick callback
  */
+#ifndef arch_irq_work_raise
 static inline void arch_irq_work_raise(void) { }
+#endif
+
+/*
+ * Unless told otherwise, consider the arch implements irq work
+ * through a hook to the timer tick.
+ */
+#ifndef arch_irq_work_use_tick
+static inline bool arch_irq_work_use_tick(void)
+{
+	return true;
+}
+#endif
 
 #endif
diff --git a/kernel/timer.c b/kernel/timer.c
index d5de1b2..6a6d1b1 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1351,7 +1351,7 @@ void update_process_times(int user_tick)
 	rcu_check_callbacks(cpu, user_tick);
 	printk_tick();
 #ifdef CONFIG_IRQ_WORK
-	if (in_irq())
+	if (arch_irq_work_use_tick() && in_irq())
 		irq_work_run();
 #endif
 	scheduler_tick();
-- 
1.7.5.4

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