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Subject[PATCH v1 1/6] 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 4e1a1bf8d867..0f5cd1b08dbd 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6299,6 +6299,12 @@ 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) {
@@ -6313,6 +6319,8 @@ static void perf_event_addr_filters_exec(struct perf_event *event, void *data)
event->addr_filters_gen++;
raw_spin_unlock_irqrestore(&ifh->lock, flags);

+ perf_pmu_enable(event->pmu);
+
if (restart)
perf_event_stop(event, 1);
}
@@ -6993,6 +7001,8 @@ 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,
@@ -7008,6 +7018,8 @@ static void __perf_addr_filters_adjust(struct perf_event *event, void *data)
event->addr_filters_gen++;
raw_spin_unlock_irqrestore(&ifh->lock, flags);

+ perf_pmu_enable(event->pmu);
+
if (restart)
perf_event_stop(event, 1);
}
@@ -8261,6 +8273,8 @@ 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;
@@ -8279,6 +8293,8 @@ 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);
--
2.17.1
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