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    Subject[RFC PATCH 5/6] perf: Disable PMU around address filter adjustment
    Date
    If the PMU is used for AUX data sampling, the hardware event that triggers
    it may come in during a critical section of address filters adjustment (if
    it's delivered as NMI) and in turn call the address filter sync code,
    causing a spinlock recursion.

    To prevent this, disable the PMU around these critical sections, so that
    AUX sampling won't take place there.

    Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    ---
    kernel/events/core.c | 16 ++++++++++++++++
    1 file changed, 16 insertions(+)

    diff --git a/kernel/events/core.c b/kernel/events/core.c
    index fdb20fdeb1..f6582df1c9 100644
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -6377,6 +6377,12 @@ static void perf_event_addr_filters_exec(struct perf_event *event, void *data)
    if (!has_addr_filter(event))
    return;

    + /*
    + * if sampling kicks in in the critical section,
    + * we risk spinlock recursion on the ifh::lock
    + */
    + perf_pmu_disable(event->pmu);
    +
    raw_spin_lock_irqsave(&ifh->lock, flags);
    list_for_each_entry(filter, &ifh->list, entry) {
    if (filter->inode) {
    @@ -6387,6 +6393,8 @@ static void perf_event_addr_filters_exec(struct perf_event *event, void *data)
    count++;
    }

    + perf_pmu_enable(event->pmu);
    +
    if (restart)
    event->addr_filters_gen++;
    raw_spin_unlock_irqrestore(&ifh->lock, flags);
    @@ -6942,6 +6950,8 @@ static void __perf_addr_filters_adjust(struct perf_event *event, void *data)
    if (!file)
    return;

    + perf_pmu_disable(event->pmu);
    +
    raw_spin_lock_irqsave(&ifh->lock, flags);
    list_for_each_entry(filter, &ifh->list, entry) {
    if (perf_addr_filter_match(filter, file, off,
    @@ -6953,6 +6963,8 @@ static void __perf_addr_filters_adjust(struct perf_event *event, void *data)
    count++;
    }

    + perf_pmu_enable(event->pmu);
    +
    if (restart)
    event->addr_filters_gen++;
    raw_spin_unlock_irqrestore(&ifh->lock, flags);
    @@ -8126,6 +8138,8 @@ static void perf_event_addr_filters_apply(struct perf_event *event)

    down_read(&mm->mmap_sem);

    + perf_pmu_disable(event->pmu);
    +
    raw_spin_lock_irqsave(&ifh->lock, flags);
    list_for_each_entry(filter, &ifh->list, entry) {
    event->addr_filters_offs[count] = 0;
    @@ -8144,6 +8158,8 @@ static void perf_event_addr_filters_apply(struct perf_event *event)
    event->addr_filters_gen++;
    raw_spin_unlock_irqrestore(&ifh->lock, flags);

    + perf_pmu_enable(event->pmu);
    +
    up_read(&mm->mmap_sem);

    mmput(mm);
    --
    2.9.3
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