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>

1 files changed, 4 insertions, 4 deletions

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 91fd0c70a18a..44edb03fc9ec 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;