[tip:perf/urgent] perf, x86: Avoid double disable on throttle vs ioctl(PERF_IOC_DISABLE)

tip-bot for Peter Zijlstra
2010-03-10T13:12:57Z

Commit-ID: 71e2d2828046133ed985696a02e2e1499ca0bfb8
Gitweb: http://git.kernel.org/tip/71e2d2828046133ed985696a02e2e1499ca0bfb8
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Mon, 8 Mar 2010 17:51:33 +0100
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 10 Mar 2010 13:22:31 +0100

perf, x86: Avoid double disable on throttle vs ioctl(PERF_IOC_DISABLE)

Calling ioctl(PERF_EVENT_IOC_DISABLE) on a thottled counter would result
in a double disable, cure this by using x86_pmu_{start,stop} for
throttle/unthrottle and teach x86_pmu_stop() to check ->active_mask.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: paulus@samba.org
Cc: eranian@google.com
Cc: robert.richter@amd.com
Cc: fweisbec@gmail.com
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86/kernel/cpu/perf_event.c | 20 ++++++--------------
arch/x86/kernel/cpu/perf_event_intel.c | 2 +-
2 files changed, 7 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 9757b96..b68c4fb 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -983,14 +983,8 @@ static int x86_pmu_start(struct perf_event *event)

static void x86_pmu_unthrottle(struct perf_event *event)
{
- struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
- struct hw_perf_event *hwc = &event->hw;
-
- if (WARN_ON_ONCE(hwc->idx >= X86_PMC_IDX_MAX ||
- cpuc->events[hwc->idx] != event))
- return;
-
- x86_pmu.enable(event);
+ int ret = x86_pmu_start(event);
+ WARN_ON_ONCE(ret);
}

void perf_event_print_debug(void)
@@ -1050,11 +1044,9 @@ static void x86_pmu_stop(struct perf_event *event)
struct hw_perf_event *hwc = &event->hw;
int idx = hwc->idx;

- /*
- * Must be done before we disable, otherwise the nmi handler
- * could reenable again:
- */
- __clear_bit(idx, cpuc->active_mask);
+ if (!__test_and_clear_bit(idx, cpuc->active_mask))
+ return;
+
x86_pmu.disable(event);

/*
@@ -1123,7 +1115,7 @@ static int x86_pmu_handle_irq(struct pt_regs *regs)
continue;

if (perf_event_overflow(event, 1, &data, regs))
- x86_pmu.disable(event);
+ x86_pmu_stop(event);
}

if (handled)
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index d87421c..84bfde6 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -774,7 +774,7 @@ again:
data.period = event->hw.last_period;

if (perf_event_overflow(event, 1, &data, regs))
- intel_pmu_disable_event(event);
+ x86_pmu_stop(event);
}

intel_pmu_ack_status(ack);