perf_counter: x86: self-IPI for pending work

Implement set_perf_counter_pending() with a self-IPI so that it will
run ASAP in a usable context.

For now use a second IRQ vector, because the primary vector pokes
the apic in funny ways that seem to confuse things.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090406094517.724626696@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 14 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index c74e20d593a..438415866fe 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -849,6 +849,20 @@ void smp_perf_counter_interrupt(struct pt_regs *regs)
 	irq_exit();
 }
 
+void smp_perf_pending_interrupt(struct pt_regs *regs)
+{
+	irq_enter();
+	ack_APIC_irq();
+	inc_irq_stat(apic_pending_irqs);
+	perf_counter_do_pending();
+	irq_exit();
+}
+
+void set_perf_counter_pending(void)
+{
+	apic->send_IPI_self(LOCAL_PENDING_VECTOR);
+}
+
 void perf_counters_lapic_init(int nmi)
 {
 	u32 apic_val;