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

From: Frederic Weisbecker
Date: Fri Oct 12 2012 - 14:09:39 EST


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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