perf, x86: P4 PMU -- update nmi irq statistics and unmask lvt entry properly

commit 1c250d709fdc8aa5bf42d90be99428a01a256a55 upstream.

In case if last active performance counter is not overflowed at
moment of NMI being triggered by another counter, the irq
statistics may miss an update stage. As a more serious
consequence -- apic quirk may not be triggered so apic lvt entry
stay masked.

Tested-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20100805150917.GA6311@lenovo>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c
index ae85d69644d182f31c9711eba6c5ddb21862bcec..0ffe19e9373adf933b4fe08a12599623758a27c8 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event_p4.c
+++ b/arch/x86/kernel/cpu/perf_event_p4.c
@@ -581,6 +581,7 @@ static int p4_pmu_handle_irq(struct pt_regs *regs)
        cpuc = &__get_cpu_var(cpu_hw_events);
 
        for (idx = 0; idx < x86_pmu.num_counters; idx++) {
+               int overflow;
 
                if (!test_bit(idx, cpuc->active_mask))
                        continue;
@@ -591,12 +592,14 @@ static int p4_pmu_handle_irq(struct pt_regs *regs)
                WARN_ON_ONCE(hwc->idx != idx);
 
                /* it might be unflagged overflow */
-               handled = p4_pmu_clear_cccr_ovf(hwc);
+               overflow = p4_pmu_clear_cccr_ovf(hwc);
 
                val = x86_perf_event_update(event);
-               if (!handled && (val & (1ULL << (x86_pmu.cntval_bits - 1))))
+               if (!overflow && (val & (1ULL << (x86_pmu.cntval_bits - 1))))
                        continue;
 
+               handled += overflow;
+
                /* event overflow for sure */
                data.period = event->hw.last_period;
 
@@ -612,7 +615,7 @@ static int p4_pmu_handle_irq(struct pt_regs *regs)
                inc_irq_stat(apic_perf_irqs);
        }
 
-       return handled;
+       return handled > 0;
 }
 
 /*