irq_work: Add generic hardirq context callbacks

Provide a mechanism that allows running code in IRQ context. It is
most useful for NMI code that needs to interact with the rest of the
system -- like wakeup a task to drain buffers.

Perf currently has such a mechanism, so extract that and provide it as
a generic feature, independent of perf so that others may also
benefit.

The IRQ context callback is generated through self-IPIs where
possible, or on architectures like powerpc the decrementer (the
built-in timer facility) is set to generate an interrupt immediately.

Architectures that don't have anything like this get to do with a
callback from the timer tick. These architectures can call
irq_work_run() at the tail of any IRQ handlers that might enqueue such
work (like the perf IRQ handler) to avoid undue latencies in
processing the work.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Kyle McMartin <kyle@mcmartin.ca>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
[ various fixes ]
Signed-off-by: Huang Ying <ying.huang@intel.com>
LKML-Reference: <1287036094.7768.291.camel@yhuang-dev>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

6 files changed, 41 insertions, 29 deletions

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 9d3f485e5dd..7490bf8d145 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -35,6 +35,7 @@ obj-y			:= process_$(BITS).o signal.o entry_$(BITS).o
 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 jump_label.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
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index e2513f26ba8..fe73c1844a9 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1196,25 +1196,6 @@ static int x86_pmu_handle_irq(struct pt_regs *regs)
         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())
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 17be5ec7cbb..c375c79065f 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/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
-apicinterrupt LOCAL_PENDING_VECTOR \
-        perf_pending_interrupt smp_perf_pending_interrupt
+#ifdef CONFIG_IRQ_WORK
+apicinterrupt IRQ_WORK_VECTOR \
+        irq_work_interrupt smp_irq_work_interrupt
 #endif
 
 /*
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 91fd0c70a18..44edb03fc9e 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -67,10 +67,10 @@ static int show_other_interrupts(struct seq_file *p, int prec)
         for_each_online_cpu(j)
                 seq_printf(p, "%10u ", irq_stats(j)->apic_perf_irqs);
         seq_printf(p, "  Performance monitoring interrupts\n");
-        seq_printf(p, "%*s: ", prec, "PND");
+        seq_printf(p, "%*s: ", prec, "IWI");
         for_each_online_cpu(j)
-                seq_printf(p, "%10u ", irq_stats(j)->apic_pending_irqs);
-        seq_printf(p, "  Performance pending work\n");
+                seq_printf(p, "%10u ", irq_stats(j)->apic_irq_work_irqs);
+        seq_printf(p, "  IRQ work interrupts\n");
 #endif
         if (x86_platform_ipi_callback) {
                 seq_printf(p, "%*s: ", prec, "PLT");
@@ -185,7 +185,7 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
         sum += irq_stats(cpu)->apic_timer_irqs;
         sum += irq_stats(cpu)->irq_spurious_count;
         sum += irq_stats(cpu)->apic_perf_irqs;
-        sum += irq_stats(cpu)->apic_pending_irqs;
+        sum += irq_stats(cpu)->apic_irq_work_irqs;
 #endif
         if (x86_platform_ipi_callback)
                 sum += irq_stats(cpu)->x86_platform_ipis;
diff --git a/arch/x86/kernel/irq_work.c b/arch/x86/kernel/irq_work.c
new file mode 100644
index 00000000000..ca8f703a1e7
--- /dev/null
+++ b/arch/x86/kernel/irq_work.c
@@ -0,0 +1,30 @@
+/*
+ * x86 specific code for irq_work
+ *
+ * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/irq_work.h>
+#include <linux/hardirq.h>
+#include <asm/apic.h>
+
+void smp_irq_work_interrupt(struct pt_regs *regs)
+{
+        irq_enter();
+        ack_APIC_irq();
+        inc_irq_stat(apic_irq_work_irqs);
+        irq_work_run();
+        irq_exit();
+}
+
+void arch_irq_work_raise(void)
+{
+#ifdef CONFIG_X86_LOCAL_APIC
+        if (!cpu_has_apic)
+                return;
+
+        apic->send_IPI_self(IRQ_WORK_VECTOR);
+        apic_wait_icr_idle();
+#endif
+}
diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
index 990ae7cfc57..713969b9266 100644
--- a/arch/x86/kernel/irqinit.c
+++ b/arch/x86/kernel/irqinit.c
@@ -224,9 +224,9 @@ static void __init apic_intr_init(void)
         alloc_intr_gate(SPURIOUS_APIC_VECTOR, spurious_interrupt);
         alloc_intr_gate(ERROR_APIC_VECTOR, error_interrupt);
 
-        /* Performance monitoring interrupts: */
-# ifdef CONFIG_PERF_EVENTS
-        alloc_intr_gate(LOCAL_PENDING_VECTOR, perf_pending_interrupt);
+        /* IRQ work interrupts: */
+# ifdef CONFIG_IRQ_WORK
+        alloc_intr_gate(IRQ_WORK_VECTOR, irq_work_interrupt);
 # endif
 
 #endif