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>

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;

arch/x86/kernel/entry_64.S

@@ -1028,6 +1028,8 @@ apicinterrupt SPURIOUS_APIC_VECTOR \
 #ifdef CONFIG_PERF_COUNTERS
 apicinterrupt LOCAL_PERF_VECTOR \
 	perf_counter_interrupt smp_perf_counter_interrupt
+apicinterrupt LOCAL_PENDING_VECTOR \
+	perf_pending_interrupt smp_perf_pending_interrupt
 #endif
 
 /*

arch/x86/kernel/irq.c

@@ -67,6 +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 counter interrupts\n");
+	seq_printf(p, "PND: ");
+	for_each_online_cpu(j)
+		seq_printf(p, "%10u ", irq_stats(j)->apic_pending_irqs);
+	seq_printf(p, "  Performance pending work\n");
 #endif
 	if (generic_interrupt_extension) {
 		seq_printf(p, "PLT: ");
@@ -171,6 +175,7 @@ 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;
 #endif
 	if (generic_interrupt_extension)
 		sum += irq_stats(cpu)->generic_irqs;

arch/x86/kernel/irqinit_32.c

@@ -166,6 +166,7 @@ static void __init apic_intr_init(void)
 	alloc_intr_gate(ERROR_APIC_VECTOR, error_interrupt);
 # ifdef CONFIG_PERF_COUNTERS
 	alloc_intr_gate(LOCAL_PERF_VECTOR, perf_counter_interrupt);
+	alloc_intr_gate(LOCAL_PENDING_VECTOR, perf_pending_interrupt);
 # endif
 
 # ifdef CONFIG_X86_MCE_P4THERMAL

arch/x86/kernel/irqinit_64.c

@@ -156,6 +156,7 @@ static void __init apic_intr_init(void)
 	/* Performance monitoring interrupt: */
 #ifdef CONFIG_PERF_COUNTERS
 	alloc_intr_gate(LOCAL_PERF_VECTOR, perf_counter_interrupt);
+	alloc_intr_gate(LOCAL_PENDING_VECTOR, perf_pending_interrupt);
 #endif
 }