[RFC][PATCH] irq_work -v2

From: Peter Zijlstra
Date: Fri Jun 25 2010 - 14:30:52 EST

Utterly untested and you really need visit all the touched architectures
if you want to make it useful.

---
Subject: irq_work: generic hard-irq context callbacks

In order for other NMI context users that want to run things from
hard-IRQ context, extract the perf_event callback mechanism.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
arch/alpha/include/asm/perf_event.h | 9 -
arch/frv/lib/perf_event.c | 19 ---
arch/parisc/include/asm/perf_event.h | 7 -
arch/s390/include/asm/perf_event.h | 10 -
linux-2.6/arch/alpha/Kconfig | 1
linux-2.6/arch/arm/Kconfig | 1
linux-2.6/arch/arm/include/asm/perf_event.h | 12 -
linux-2.6/arch/arm/kernel/perf_event.c | 4
linux-2.6/arch/frv/Kconfig | 1
linux-2.6/arch/parisc/Kconfig | 1
linux-2.6/arch/powerpc/Kconfig | 1
linux-2.6/arch/powerpc/kernel/time.c | 42 +++---
linux-2.6/arch/s390/Kconfig | 1
linux-2.6/arch/sh/Kconfig | 1
linux-2.6/arch/sh/include/asm/perf_event.h | 7 -
linux-2.6/arch/sparc/Kconfig | 2
linux-2.6/arch/sparc/include/asm/perf_event.h | 4
linux-2.6/arch/sparc/kernel/pcr.c | 8 -
linux-2.6/arch/x86/Kconfig | 1
linux-2.6/arch/x86/include/asm/entry_arch.h | 4
linux-2.6/arch/x86/include/asm/hw_irq.h | 2
linux-2.6/arch/x86/kernel/Makefile | 1
linux-2.6/arch/x86/kernel/cpu/perf_event.c | 19 ---
linux-2.6/arch/x86/kernel/entry_64.S | 4
linux-2.6/arch/x86/kernel/irq_work.c | 26 ++++
linux-2.6/arch/x86/kernel/irqinit.c | 4
linux-2.6/include/linux/irq_work.h | 20 +++
linux-2.6/include/linux/perf_event.h | 11 -
linux-2.6/init/Kconfig | 8 +
linux-2.6/kernel/Makefile | 2
linux-2.6/kernel/irq_work.c | 157 ++++++++++++++++++++++++++
linux-2.6/kernel/perf_event.c | 102 ----------------
linux-2.6/kernel/timer.c | 4
33 files changed, 266 insertions(+), 230 deletions(-)

Index: linux-2.6/include/linux/irq_work.h
===================================================================
--- /dev/null
+++ linux-2.6/include/linux/irq_work.h
@@ -0,0 +1,20 @@
+#ifndef _LINUX_IRQ_WORK_H
+#define _LINUX_IRQ_WORK_H
+
+struct irq_work {
+ struct irq_work *next;
+ void (*func)(struct irq_work *);
+};
+
+static inline
+void init_irq_work(struct irq_work *entry, void (*func)(struct irq_work *))
+{
+ entry->next = NULL;
+ entry->func = func;
+}
+
+int irq_work_queue(struct irq_work *entry);
+void irq_work_run(void);
+void irq_work_sync(struct irq_work *entry);
+
+#endif /* _LINUX_IRQ_WORK_H */
Index: linux-2.6/kernel/irq_work.c
===================================================================
--- /dev/null
+++ linux-2.6/kernel/irq_work.c
@@ -0,0 +1,157 @@
+/*
+ * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra <pzijlstr@xxxxxxxxxx>
+ *
+ * Provides a framework for enqueueing and running callbacks from hardirq
+ * context. The enqueueing is NMI-safe.
+ */
+
+#include <linux/irq_work.h>
+#include <linux/hardirq.h>
+
+/*
+ * An entry can be in one of four states:
+ *
+ * free NULL, 0 -> {claimed} : free to be used
+ * claimed NULL, 3 -> {pending} : claimed to be enqueued
+ * pending next, 3 -> {busy} : queued, pending callback
+ * busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed
+ *
+ * We use the lower two bits of the next pointer to keep PENDING and BUSY
+ * flags.
+ */
+
+#define IRQ_WORK_PENDING 1UL
+#define IRQ_WORK_BUSY 2UL
+#define IRQ_WORK_FLAGS 3UL
+
+static inline bool irq_work_is_set(struct irq_work *entry, int flags)
+{
+ return (unsigned long)entry->next & flags;
+}
+
+static inline struct irq_work *irq_work_next(struct irq_work *entry)
+{
+ unsigned long next = (unsigned long)entry->next;
+ next &= ~IRQ_WORK_FLAGS;
+ return (struct irq_work *)next;
+}
+
+static inline struct irq_work *next_flags(struct irq_work *entry, int flags)
+{
+ unsigned long next = (unsigned long)entry;
+ next |= flags;
+ return (struct irq_work *)next;
+}
+
+static DEFINE_PER_CPU(struct irq_work *, irq_work_list);
+
+/*
+ * Claim the entry so that no one else will poke at it.
+ */
+static bool irq_work_claim(struct irq_work *entry)
+{
+ unsigned long flags;
+
+ do {
+ flags = (unsigned long)entry->next;
+ if (flags & IRQ_WORK_PENDING)
+ return false;
+ } while (cmpxchg(&entry->next, flags, flags | IRQ_WORK_FLAGS) != flags);
+
+ return true;
+}
+
+
+void __weak arch_irq_work_raise(void)
+{
+ /*
+ * Lame architectures will get the timer tick callback
+ */
+}
+
+/*
+ * Queue the entry and raise the IPI if needed.
+ */
+static void __irq_work_queue(struct irq_work *entry)
+{
+ struct irq_work **head;
+
+ head = &get_cpu_var(irq_work_list);
+
+ do {
+ /*
+ * Can assign non-atomic because we keep the flags set.
+ */
+ entry->next = next_flags(*head, IRQ_WORK_FLAGS);
+ } while (cmpxchg(head, entry->next, entry) != entry->next);
+
+ /*
+ * The list was empty, raise self-interrupt to start processing.
+ */
+ if (!irq_work_next(entry))
+ arch_irq_work_raise();
+
+ put_cpu_var(irq_work_list);
+}
+
+/*
+ * Enqueue the irq_work @entry, returns true on success, failure when the
+ * @entry was already enqueued by someone else.
+ *
+ * Can be re-enqueued while the callback is still in progress.
+ */
+bool irq_work_queue(struct irq_work *entry)
+{
+ if (!irq_work_claim(entry)) {
+ /*
+ * Already enqueued, can't do!
+ */
+ return false;
+ }
+
+ __irq_work_queue(entry);
+ return true;
+}
+
+/*
+ * Run the irq_work entries on this cpu. Requires to be ran from hardirq
+ * context with local IRQs disabled.
+ */
+void irq_work_run(void)
+{
+ struct irq_work *list;
+
+ BUG_ON(!in_irq());
+ BUG_ON(!irqs_disabled());
+
+ list = xchg(&__get_cpu_var(irq_work_list), NULL);
+ while (list != NULL) {
+ struct irq_work *entry = list;
+
+ list = irq_work_next(list);
+
+ /*
+ * Clear the PENDING bit, after this point the @entry
+ * can be re-used.
+ */
+ entry->next = next_flags(NULL, IRQ_WORK_BUSY);
+ entry->func(entry);
+ /*
+ * Clear the BUSY bit and return to the free state if
+ * no-one else claimed it meanwhile.
+ */
+ cmpxchg(&entry->next, next_flags(NULL, IRQ_WORK_BUSY), NULL);
+ }
+}
+
+/*
+ * Synchronize against the irq_work @entry, ensures the entry is not
+ * currently in use.
+ */
+void irq_work_sync(struct irq_work *entry)
+{
+ WARN_ON_ONCE(irqs_disabled());
+
+ while (irq_work_is_set(entry, IRQ_WORK_BUSY))
+ cpu_relax();
+}
Index: linux-2.6/arch/alpha/Kconfig
===================================================================
--- linux-2.6.orig/arch/alpha/Kconfig
+++ linux-2.6/arch/alpha/Kconfig
@@ -9,6 +9,7 @@ config ALPHA
select HAVE_IDE
select HAVE_OPROFILE
select HAVE_SYSCALL_WRAPPERS
+ select HAVE_IRQ_WORK
select HAVE_PERF_EVENTS
select HAVE_DMA_ATTRS
help
Index: linux-2.6/arch/alpha/include/asm/perf_event.h
===================================================================
--- linux-2.6.orig/arch/alpha/include/asm/perf_event.h
+++ /dev/null
@@ -1,9 +0,0 @@
-#ifndef __ASM_ALPHA_PERF_EVENT_H
-#define __ASM_ALPHA_PERF_EVENT_H
-
-/* Alpha only supports software events through this interface. */
-static inline void set_perf_event_pending(void) { }
-
-#define PERF_EVENT_INDEX_OFFSET 0
-
-#endif /* __ASM_ALPHA_PERF_EVENT_H */
Index: linux-2.6/arch/arm/Kconfig
===================================================================
--- linux-2.6.orig/arch/arm/Kconfig
+++ linux-2.6/arch/arm/Kconfig
@@ -22,6 +22,7 @@ config ARM
select HAVE_KERNEL_GZIP
select HAVE_KERNEL_LZO
select HAVE_KERNEL_LZMA
+ select HAVE_IRQ_WORK
select HAVE_PERF_EVENTS
select PERF_USE_VMALLOC
help
Index: linux-2.6/arch/arm/include/asm/perf_event.h
===================================================================
--- linux-2.6.orig/arch/arm/include/asm/perf_event.h
+++ linux-2.6/arch/arm/include/asm/perf_event.h
@@ -12,18 +12,6 @@
#ifndef __ARM_PERF_EVENT_H__
#define __ARM_PERF_EVENT_H__

-/*
- * NOP: on *most* (read: all supported) ARM platforms, the performance
- * counter interrupts are regular interrupts and not an NMI. This
- * means that when we receive the interrupt we can call
- * perf_event_do_pending() that handles all of the work with
- * interrupts enabled.
- */
-static inline void
-set_perf_event_pending(void)
-{
-}
-
/* ARM performance counters start from 1 (in the cp15 accesses) so use the
* same indexes here for consistency. */
#define PERF_EVENT_INDEX_OFFSET 1
Index: linux-2.6/arch/frv/Kconfig
===================================================================
--- linux-2.6.orig/arch/frv/Kconfig
+++ linux-2.6/arch/frv/Kconfig
@@ -7,6 +7,7 @@ config FRV
default y
select HAVE_IDE
select HAVE_ARCH_TRACEHOOK
+ select HAVE_IRQ_WORK
select HAVE_PERF_EVENTS

config ZONE_DMA
Index: linux-2.6/arch/frv/lib/perf_event.c
===================================================================
--- linux-2.6.orig/arch/frv/lib/perf_event.c
+++ /dev/null
@@ -1,19 +0,0 @@
-/* Performance event handling
- *
- * Copyright (C) 2009 Red Hat, Inc. All Rights Reserved.
- * Written by David Howells (dhowells@xxxxxxxxxx)
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public Licence
- * as published by the Free Software Foundation; either version
- * 2 of the Licence, or (at your option) any later version.
- */
-
-#include <linux/perf_event.h>
-
-/*
- * mark the performance event as pending
- */
-void set_perf_event_pending(void)
-{
-}
Index: linux-2.6/arch/parisc/Kconfig
===================================================================
--- linux-2.6.orig/arch/parisc/Kconfig
+++ linux-2.6/arch/parisc/Kconfig
@@ -16,6 +16,7 @@ config PARISC
select RTC_DRV_GENERIC
select INIT_ALL_POSSIBLE
select BUG
+ select HAVE_IRQ_WORK
select HAVE_PERF_EVENTS
select GENERIC_ATOMIC64 if !64BIT
help
Index: linux-2.6/arch/parisc/include/asm/perf_event.h
===================================================================
--- linux-2.6.orig/arch/parisc/include/asm/perf_event.h
+++ /dev/null
@@ -1,7 +0,0 @@
-#ifndef __ASM_PARISC_PERF_EVENT_H
-#define __ASM_PARISC_PERF_EVENT_H
-
-/* parisc only supports software events through this interface. */
-static inline void set_perf_event_pending(void) { }
-
-#endif /* __ASM_PARISC_PERF_EVENT_H */
Index: linux-2.6/arch/powerpc/Kconfig
===================================================================
--- linux-2.6.orig/arch/powerpc/Kconfig
+++ linux-2.6/arch/powerpc/Kconfig
@@ -139,6 +139,7 @@ config PPC
select HAVE_OPROFILE
select HAVE_SYSCALL_WRAPPERS if PPC64
select GENERIC_ATOMIC64 if PPC32
+ select HAVE_IRQ_WORK
select HAVE_PERF_EVENTS
select HAVE_REGS_AND_STACK_ACCESS_API

Index: linux-2.6/arch/powerpc/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/powerpc/kernel/time.c
+++ linux-2.6/arch/powerpc/kernel/time.c
@@ -53,7 +53,7 @@
#include <linux/posix-timers.h>
#include <linux/irq.h>
#include <linux/delay.h>
-#include <linux/perf_event.h>
+#include <linux/irq_work.h>
#include <asm/trace.h>

#include <asm/io.h>
@@ -532,60 +532,60 @@ void __init iSeries_time_init_early(void
}
#endif /* CONFIG_PPC_ISERIES */

-#ifdef CONFIG_PERF_EVENTS
+#ifdef CONFIG_IRQ_WORK

/*
* 64-bit uses a byte in the PACA, 32-bit uses a per-cpu variable...
*/
#ifdef CONFIG_PPC64
-static inline unsigned long test_perf_event_pending(void)
+static inline unsigned long test_irq_work_pending(void)
{
unsigned long x;

asm volatile("lbz %0,%1(13)"
: "=r" (x)
- : "i" (offsetof(struct paca_struct, perf_event_pending)));
+ : "i" (offsetof(struct paca_struct, irq_work_pending)));
return x;
}

-static inline void set_perf_event_pending_flag(void)
+static inline void set_irq_work_pending_flag(void)
{
asm volatile("stb %0,%1(13)" : :
"r" (1),
- "i" (offsetof(struct paca_struct, perf_event_pending)));
+ "i" (offsetof(struct paca_struct, irq_work_pending)));
}

-static inline void clear_perf_event_pending(void)
+static inline void clear_irq_work_pending(void)
{
asm volatile("stb %0,%1(13)" : :
"r" (0),
- "i" (offsetof(struct paca_struct, perf_event_pending)));
+ "i" (offsetof(struct paca_struct, irq_work_pending)));
}

#else /* 32-bit */

-DEFINE_PER_CPU(u8, perf_event_pending);
+DEFINE_PER_CPU(u8, irq_work_pending);

-#define set_perf_event_pending_flag() __get_cpu_var(perf_event_pending) = 1
-#define test_perf_event_pending() __get_cpu_var(perf_event_pending)
-#define clear_perf_event_pending() __get_cpu_var(perf_event_pending) = 0
+#define set_irq_work_pending_flag() __get_cpu_var(irq_work_pending) = 1
+#define test_irq_work_pending() __get_cpu_var(irq_work_pending)
+#define clear_irq_work_pending() __get_cpu_var(irq_work_pending) = 0

#endif /* 32 vs 64 bit */

-void set_perf_event_pending(void)
+void set_irq_work_pending(void)
{
preempt_disable();
- set_perf_event_pending_flag();
+ set_irq_work_pending_flag();
set_dec(1);
preempt_enable();
}

-#else /* CONFIG_PERF_EVENTS */
+#else /* CONFIG_IRQ_WORK */

-#define test_perf_event_pending() 0
-#define clear_perf_event_pending()
+#define test_irq_work_pending() 0
+#define clear_irq_work_pending()

-#endif /* CONFIG_PERF_EVENTS */
+#endif /* CONFIG_IRQ_WORK */

/*
* For iSeries shared processors, we have to let the hypervisor
@@ -635,9 +635,9 @@ void timer_interrupt(struct pt_regs * re

calculate_steal_time();

- if (test_perf_event_pending()) {
- clear_perf_event_pending();
- perf_event_do_pending();
+ if (test_irq_work_pending()) {
+ clear_irq_work_pending();
+ irq_work_run();
}

#ifdef CONFIG_PPC_ISERIES
Index: linux-2.6/arch/s390/Kconfig
===================================================================
--- linux-2.6.orig/arch/s390/Kconfig
+++ linux-2.6/arch/s390/Kconfig
@@ -98,6 +98,7 @@ config S390
select HAVE_KVM if 64BIT
select HAVE_ARCH_TRACEHOOK
select INIT_ALL_POSSIBLE
+ select HAVE_IRQ_WORK
select HAVE_PERF_EVENTS
select HAVE_KERNEL_GZIP
select HAVE_KERNEL_BZIP2
Index: linux-2.6/arch/s390/include/asm/perf_event.h
===================================================================
--- linux-2.6.orig/arch/s390/include/asm/perf_event.h
+++ /dev/null
@@ -1,10 +0,0 @@
-/*
- * Performance event support - s390 specific definitions.
- *
- * Copyright 2009 Martin Schwidefsky, IBM Corporation.
- */
-
-static inline void set_perf_event_pending(void) {}
-static inline void clear_perf_event_pending(void) {}
-
-#define PERF_EVENT_INDEX_OFFSET 0
Index: linux-2.6/arch/sh/Kconfig
===================================================================
--- linux-2.6.orig/arch/sh/Kconfig
+++ linux-2.6/arch/sh/Kconfig
@@ -16,6 +16,7 @@ config SUPERH
select HAVE_ARCH_TRACEHOOK
select HAVE_DMA_API_DEBUG
select HAVE_DMA_ATTRS
+ select HAVE_IRQ_WORK
select HAVE_PERF_EVENTS
select PERF_USE_VMALLOC
select HAVE_KERNEL_GZIP
Index: linux-2.6/arch/sh/include/asm/perf_event.h
===================================================================
--- linux-2.6.orig/arch/sh/include/asm/perf_event.h
+++ linux-2.6/arch/sh/include/asm/perf_event.h
@@ -26,11 +26,4 @@ extern int register_sh_pmu(struct sh_pmu
extern int reserve_pmc_hardware(void);
extern void release_pmc_hardware(void);

-static inline void set_perf_event_pending(void)
-{
- /* Nothing to see here, move along. */
-}
-
-#define PERF_EVENT_INDEX_OFFSET 0
-
#endif /* __ASM_SH_PERF_EVENT_H */
Index: linux-2.6/arch/sparc/Kconfig
===================================================================
--- linux-2.6.orig/arch/sparc/Kconfig
+++ linux-2.6/arch/sparc/Kconfig
@@ -25,6 +25,7 @@ config SPARC
select ARCH_WANT_OPTIONAL_GPIOLIB
select RTC_CLASS
select RTC_DRV_M48T59
+ select HAVE_IRQ_WORK
select HAVE_PERF_EVENTS
select PERF_USE_VMALLOC
select HAVE_DMA_ATTRS
@@ -52,6 +53,7 @@ config SPARC64
select RTC_DRV_BQ4802
select RTC_DRV_SUN4V
select RTC_DRV_STARFIRE
+ select HAVE_IRQ_WORK
select HAVE_PERF_EVENTS
select PERF_USE_VMALLOC

Index: linux-2.6/arch/sparc/include/asm/perf_event.h
===================================================================
--- linux-2.6.orig/arch/sparc/include/asm/perf_event.h
+++ linux-2.6/arch/sparc/include/asm/perf_event.h
@@ -1,10 +1,6 @@
#ifndef __ASM_SPARC_PERF_EVENT_H
#define __ASM_SPARC_PERF_EVENT_H

-extern void set_perf_event_pending(void);
-
-#define PERF_EVENT_INDEX_OFFSET 0
-
#ifdef CONFIG_PERF_EVENTS
#include <asm/ptrace.h>

Index: linux-2.6/arch/sparc/kernel/pcr.c
===================================================================
--- linux-2.6.orig/arch/sparc/kernel/pcr.c
+++ linux-2.6/arch/sparc/kernel/pcr.c
@@ -7,7 +7,7 @@
#include <linux/init.h>
#include <linux/irq.h>

-#include <linux/perf_event.h>
+#include <linux/irq_work.h>
#include <linux/ftrace.h>

#include <asm/pil.h>
@@ -43,14 +43,14 @@ void __irq_entry deferred_pcr_work_irq(i

old_regs = set_irq_regs(regs);
irq_enter();
-#ifdef CONFIG_PERF_EVENTS
- perf_event_do_pending();
+#ifdef CONFIG_IRQ_WORK
+ irq_work_run();
#endif
irq_exit();
set_irq_regs(old_regs);
}

-void set_perf_event_pending(void)
+void arch_irq_work_raise(void)
{
set_softint(1 << PIL_DEFERRED_PCR_WORK);
}
Index: linux-2.6/arch/x86/Kconfig
===================================================================
--- linux-2.6.orig/arch/x86/Kconfig
+++ linux-2.6/arch/x86/Kconfig
@@ -55,6 +55,7 @@ config X86
select HAVE_HW_BREAKPOINT
select HAVE_MIXED_BREAKPOINTS_REGS
select PERF_EVENTS
+ select HAVE_IRQ_WORK
select HAVE_PERF_EVENTS_NMI
select ANON_INODES
select HAVE_ARCH_KMEMCHECK
Index: linux-2.6/arch/x86/include/asm/entry_arch.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/entry_arch.h
+++ linux-2.6/arch/x86/include/asm/entry_arch.h
@@ -49,8 +49,8 @@ BUILD_INTERRUPT(apic_timer_interrupt,LOC
BUILD_INTERRUPT(error_interrupt,ERROR_APIC_VECTOR)
BUILD_INTERRUPT(spurious_interrupt,SPURIOUS_APIC_VECTOR)

-#ifdef CONFIG_PERF_EVENTS
-BUILD_INTERRUPT(perf_pending_interrupt, LOCAL_PENDING_VECTOR)
+#ifdef CONFIG_IRQ_WORK
+BUILD_INTERRUPT(irq_work_interrupt,LOCAL_PENDING_VECTOR)
#endif

#ifdef CONFIG_X86_THERMAL_VECTOR
Index: linux-2.6/arch/x86/include/asm/hw_irq.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/hw_irq.h
+++ linux-2.6/arch/x86/include/asm/hw_irq.h
@@ -29,7 +29,7 @@
extern void apic_timer_interrupt(void);
extern void x86_platform_ipi(void);
extern void error_interrupt(void);
-extern void perf_pending_interrupt(void);
+extern void irq_work_interrupt(void);

extern void spurious_interrupt(void);
extern void thermal_interrupt(void);
Index: linux-2.6/arch/x86/kernel/Makefile
===================================================================
--- linux-2.6.orig/arch/x86/kernel/Makefile
+++ linux-2.6/arch/x86/kernel/Makefile
@@ -33,6 +33,7 @@ obj-y := process_$(BITS).o signal.o en
obj-y += traps.o irq.o irq_$(BITS).o dumpstack_$(BITS).o
obj-y += time.o ioport.o ldt.o dumpstack.o
obj-y += setup.o x86_init.o i8259.o irqinit.o
+obj-$(CONFIG_IRQ_WORK) += irq_work.o
obj-$(CONFIG_X86_VISWS) += visws_quirks.o
obj-$(CONFIG_X86_32) += probe_roms_32.o
obj-$(CONFIG_X86_32) += sys_i386_32.o i386_ksyms_32.o
Index: linux-2.6/arch/x86/kernel/cpu/perf_event.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event.c
@@ -1170,25 +1170,6 @@ static int x86_pmu_handle_irq(struct pt_
return handled;
}

-void smp_perf_pending_interrupt(struct pt_regs *regs)
-{
- irq_enter();
- ack_APIC_irq();
- inc_irq_stat(apic_pending_irqs);
- perf_event_do_pending();
- irq_exit();
-}
-
-void set_perf_event_pending(void)
-{
-#ifdef CONFIG_X86_LOCAL_APIC
- if (!x86_pmu.apic || !x86_pmu_initialized())
- return;
-
- apic->send_IPI_self(LOCAL_PENDING_VECTOR);
-#endif
-}
-
void perf_events_lapic_init(void)
{
if (!x86_pmu.apic || !x86_pmu_initialized())
Index: linux-2.6/arch/x86/kernel/entry_64.S
===================================================================
--- linux-2.6.orig/arch/x86/kernel/entry_64.S
+++ linux-2.6/arch/x86/kernel/entry_64.S
@@ -1023,9 +1023,9 @@ apicinterrupt ERROR_APIC_VECTOR \
apicinterrupt SPURIOUS_APIC_VECTOR \
spurious_interrupt smp_spurious_interrupt

-#ifdef CONFIG_PERF_EVENTS
+#ifdef CONFIG_IRQ_WORK
apicinterrupt LOCAL_PENDING_VECTOR \
- perf_pending_interrupt smp_perf_pending_interrupt
+ irq_work_interrupt smp_irq_work_interrupt
#endif

/*
Index: linux-2.6/arch/x86/kernel/irq_work.c
===================================================================
--- /dev/null
+++ linux-2.6/arch/x86/kernel/irq_work.c
@@ -0,0 +1,26 @@
+
+#include <linux/irq_work.h>
+#include <linux/hardirq.h>
+#include <asm/apic.h>
+
+void smp_perf_pending_interrupt(struct pt_regs *regs)
+{
+ irq_enter();
+ ack_APIC_irq();
+ inc_irq_stat(apic_pending_irqs);
+ irq_work_run();
+ irq_exit();
+}
+
+void arch_irq_work_raise(void)
+{
+#ifdef CONFIG_X86_LOCAL_APIC
+ if (!cpu_as_apic)
+ return;
+
+ apic->send_IPI_self(LOCAL_PENDING_VECTOR);
+ apic_wait_icr_idle();
+#endif
+}
+
+
Index: linux-2.6/arch/x86/kernel/irqinit.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/irqinit.c
+++ linux-2.6/arch/x86/kernel/irqinit.c
@@ -225,8 +225,8 @@ static void __init apic_intr_init(void)
alloc_intr_gate(ERROR_APIC_VECTOR, error_interrupt);

/* Performance monitoring interrupts: */
-# ifdef CONFIG_PERF_EVENTS
- alloc_intr_gate(LOCAL_PENDING_VECTOR, perf_pending_interrupt);
+# ifdef CONFIG_IRQ_WORK
+ alloc_intr_gate(LOCAL_PENDING_VECTOR, irq_work_interrupt);
# endif

#endif
Index: linux-2.6/include/linux/perf_event.h
===================================================================
--- linux-2.6.orig/include/linux/perf_event.h
+++ linux-2.6/include/linux/perf_event.h
@@ -486,6 +486,7 @@ struct perf_guest_info_callbacks {
#include <linux/workqueue.h>
#include <linux/ftrace.h>
#include <linux/cpu.h>
+#include <linux/irq_work.h>
#include <asm/atomic.h>
#include <asm/local.h>

@@ -629,11 +630,6 @@ struct perf_buffer {
void *data_pages[0];
};

-struct perf_pending_entry {
- struct perf_pending_entry *next;
- void (*func)(struct perf_pending_entry *);
-};
-
struct perf_sample_data;

typedef void (*perf_overflow_handler_t)(struct perf_event *, int,
@@ -741,7 +737,7 @@ struct perf_event {
int pending_wakeup;
int pending_kill;
int pending_disable;
- struct perf_pending_entry pending;
+ struct irq_work pending;

atomic_t event_limit;

@@ -853,8 +849,6 @@ extern void perf_event_task_tick(struct
extern int perf_event_init_task(struct task_struct *child);
extern void perf_event_exit_task(struct task_struct *child);
extern void perf_event_free_task(struct task_struct *task);
-extern void set_perf_event_pending(void);
-extern void perf_event_do_pending(void);
extern void perf_event_print_debug(void);
extern void __perf_disable(void);
extern bool __perf_enable(void);
@@ -1028,7 +1022,6 @@ perf_event_task_tick(struct task_struct
static inline int perf_event_init_task(struct task_struct *child) { return 0; }
static inline void perf_event_exit_task(struct task_struct *child) { }
static inline void perf_event_free_task(struct task_struct *task) { }
-static inline void perf_event_do_pending(void) { }
static inline void perf_event_print_debug(void) { }
static inline void perf_disable(void) { }
static inline void perf_enable(void) { }
Index: linux-2.6/init/Kconfig
===================================================================
--- linux-2.6.orig/init/Kconfig
+++ linux-2.6/init/Kconfig
@@ -21,6 +21,13 @@ config CONSTRUCTORS
depends on !UML
default y

+config HAVE_IRQ_WORK
+ bool
+
+config IRQ_WORK
+ bool
+ depends on HAVE_IRQ_WORK
+
menu "General setup"

config EXPERIMENTAL
@@ -983,6 +990,7 @@ config PERF_EVENTS
default y if (PROFILING || PERF_COUNTERS)
depends on HAVE_PERF_EVENTS
select ANON_INODES
+ select IRQ_WORK
help
Enable kernel support for various performance events provided
by software and hardware.
Index: linux-2.6/kernel/Makefile
===================================================================
--- linux-2.6.orig/kernel/Makefile
+++ linux-2.6/kernel/Makefile
@@ -23,6 +23,7 @@ CFLAGS_REMOVE_rtmutex-debug.o = -pg
CFLAGS_REMOVE_cgroup-debug.o = -pg
CFLAGS_REMOVE_sched_clock.o = -pg
CFLAGS_REMOVE_perf_event.o = -pg
+CFLAGS_REMOVE_irq_work.o = -pg
endif

obj-$(CONFIG_FREEZER) += freezer.o
@@ -101,6 +102,7 @@ obj-$(CONFIG_RING_BUFFER) += trace/
obj-$(CONFIG_SMP) += sched_cpupri.o
obj-$(CONFIG_SLOW_WORK) += slow-work.o
obj-$(CONFIG_SLOW_WORK_DEBUG) += slow-work-debugfs.o
+obj-$(CONFIG_IRQ_WORK) += irq_work.o
obj-$(CONFIG_PERF_EVENTS) += perf_event.o
obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -1880,12 +1880,11 @@ static void free_event_rcu(struct rcu_he
kfree(event);
}

-static void perf_pending_sync(struct perf_event *event);
static void perf_buffer_put(struct perf_buffer *buffer);

static void free_event(struct perf_event *event)
{
- perf_pending_sync(event);
+ irq_work_sync(&event->pending);

if (!event->parent) {
atomic_dec(&nr_events);
@@ -2829,15 +2828,6 @@ void perf_event_wakeup(struct perf_event
}
}

-/*
- * Pending wakeups
- *
- * Handle the case where we need to wakeup up from NMI (or rq->lock) context.
- *
- * The NMI bit means we cannot possibly take locks. Therefore, maintain a
- * single linked list and use cmpxchg() to add entries lockless.
- */
-
static void perf_pending_event(struct perf_pending_entry *entry)
{
struct perf_event *event = container_of(entry,
@@ -2854,89 +2844,6 @@ static void perf_pending_event(struct pe
}
}

-#define PENDING_TAIL ((struct perf_pending_entry *)-1UL)
-
-static DEFINE_PER_CPU(struct perf_pending_entry *, perf_pending_head) = {
- PENDING_TAIL,
-};
-
-static void perf_pending_queue(struct perf_pending_entry *entry,
- void (*func)(struct perf_pending_entry *))
-{
- struct perf_pending_entry **head;
-
- if (cmpxchg(&entry->next, NULL, PENDING_TAIL) != NULL)
- return;
-
- entry->func = func;
-
- head = &get_cpu_var(perf_pending_head);
-
- do {
- entry->next = *head;
- } while (cmpxchg(head, entry->next, entry) != entry->next);
-
- set_perf_event_pending();
-
- put_cpu_var(perf_pending_head);
-}
-
-static int __perf_pending_run(void)
-{
- struct perf_pending_entry *list;
- int nr = 0;
-
- list = xchg(&__get_cpu_var(perf_pending_head), PENDING_TAIL);
- while (list != PENDING_TAIL) {
- void (*func)(struct perf_pending_entry *);
- struct perf_pending_entry *entry = list;
-
- list = list->next;
-
- func = entry->func;
- entry->next = NULL;
- /*
- * Ensure we observe the unqueue before we issue the wakeup,
- * so that we won't be waiting forever.
- * -- see perf_not_pending().
- */
- smp_wmb();
-
- func(entry);
- nr++;
- }
-
- return nr;
-}
-
-static inline int perf_not_pending(struct perf_event *event)
-{
- /*
- * If we flush on whatever cpu we run, there is a chance we don't
- * need to wait.
- */
- get_cpu();
- __perf_pending_run();
- put_cpu();
-
- /*
- * Ensure we see the proper queue state before going to sleep
- * so that we do not miss the wakeup. -- see perf_pending_handle()
- */
- smp_rmb();
- return event->pending.next == NULL;
-}
-
-static void perf_pending_sync(struct perf_event *event)
-{
- wait_event(event->waitq, perf_not_pending(event));
-}
-
-void perf_event_do_pending(void)
-{
- __perf_pending_run();
-}
-
/*
* Callchain support -- arch specific
*/
@@ -2996,8 +2903,7 @@ static void perf_output_wakeup(struct pe

if (handle->nmi) {
handle->event->pending_wakeup = 1;
- perf_pending_queue(&handle->event->pending,
- perf_pending_event);
+ irq_work_queue(&handle->event->pending);
} else
perf_event_wakeup(handle->event);
}
@@ -3988,8 +3894,7 @@ static int __perf_event_overflow(struct
event->pending_kill = POLL_HUP;
if (nmi) {
event->pending_disable = 1;
- perf_pending_queue(&event->pending,
- perf_pending_event);
+ irq_work_queue(&event->pending);
} else
perf_event_disable(event);
}
@@ -4841,6 +4746,7 @@ perf_event_alloc(struct perf_event_attr
INIT_LIST_HEAD(&event->event_entry);
INIT_LIST_HEAD(&event->sibling_list);
init_waitqueue_head(&event->waitq);
+ irq_work_init(&event->pending, perf_pending_event);

mutex_init(&event->mmap_mutex);

Index: linux-2.6/kernel/timer.c
===================================================================
--- linux-2.6.orig/kernel/timer.c
+++ linux-2.6/kernel/timer.c
@@ -37,7 +37,7 @@
#include <linux/delay.h>
#include <linux/tick.h>
#include <linux/kallsyms.h>
-#include <linux/perf_event.h>
+#include <linux/irq_work.h>
#include <linux/sched.h>
#include <linux/slab.h>

@@ -1260,7 +1260,7 @@ void update_process_times(int user_tick)
run_local_timers();
rcu_check_callbacks(cpu, user_tick);
printk_tick();
- perf_event_do_pending();
+ irq_work_run();
scheduler_tick();
run_posix_cpu_timers(p);
}
Index: linux-2.6/arch/arm/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/arch/arm/kernel/perf_event.c
+++ linux-2.6/arch/arm/kernel/perf_event.c
@@ -1045,7 +1045,7 @@ armv6pmu_handle_irq(int irq_num,
* platforms that can have the PMU interrupts raised as a PMI, this
* will not work.
*/
- perf_event_do_pending();
+ irq_work_run();

return IRQ_HANDLED;
}
@@ -2021,7 +2021,7 @@ static irqreturn_t armv7pmu_handle_irq(i
* platforms that can have the PMU interrupts raised as a PMI, this
* will not work.
*/
- perf_event_do_pending();
+ irq_work_run();

return IRQ_HANDLED;
}

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