summaryrefslogtreecommitdiff
path: root/kernel/events/core.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/events/core.c')
-rw-r--r--kernel/events/core.c78
1 files changed, 78 insertions, 0 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index ae16867670a9..e8183895691c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3222,6 +3222,59 @@ static inline u64 perf_event_count(struct perf_event *event)
return __perf_event_count(event);
}
+/*
+ * NMI-safe method to read a local event, that is an event that
+ * is:
+ * - either for the current task, or for this CPU
+ * - does not have inherit set, for inherited task events
+ * will not be local and we cannot read them atomically
+ * - must not have a pmu::count method
+ */
+u64 perf_event_read_local(struct perf_event *event)
+{
+ unsigned long flags;
+ u64 val;
+
+ /*
+ * Disabling interrupts avoids all counter scheduling (context
+ * switches, timer based rotation and IPIs).
+ */
+ local_irq_save(flags);
+
+ /* If this is a per-task event, it must be for current */
+ WARN_ON_ONCE((event->attach_state & PERF_ATTACH_TASK) &&
+ event->hw.target != current);
+
+ /* If this is a per-CPU event, it must be for this CPU */
+ WARN_ON_ONCE(!(event->attach_state & PERF_ATTACH_TASK) &&
+ event->cpu != smp_processor_id());
+
+ /*
+ * It must not be an event with inherit set, we cannot read
+ * all child counters from atomic context.
+ */
+ WARN_ON_ONCE(event->attr.inherit);
+
+ /*
+ * It must not have a pmu::count method, those are not
+ * NMI safe.
+ */
+ WARN_ON_ONCE(event->pmu->count);
+
+ /*
+ * If the event is currently on this CPU, its either a per-task event,
+ * or local to this CPU. Furthermore it means its ACTIVE (otherwise
+ * oncpu == -1).
+ */
+ if (event->oncpu == smp_processor_id())
+ event->pmu->read(event);
+
+ val = local64_read(&event->count);
+ local_irq_restore(flags);
+
+ return val;
+}
+
static u64 perf_event_read(struct perf_event *event)
{
/*
@@ -8718,6 +8771,31 @@ void perf_event_delayed_put(struct task_struct *task)
WARN_ON_ONCE(task->perf_event_ctxp[ctxn]);
}
+struct perf_event *perf_event_get(unsigned int fd)
+{
+ int err;
+ struct fd f;
+ struct perf_event *event;
+
+ err = perf_fget_light(fd, &f);
+ if (err)
+ return ERR_PTR(err);
+
+ event = f.file->private_data;
+ atomic_long_inc(&event->refcount);
+ fdput(f);
+
+ return event;
+}
+
+const struct perf_event_attr *perf_event_attrs(struct perf_event *event)
+{
+ if (!event)
+ return ERR_PTR(-EINVAL);
+
+ return &event->attr;
+}
+
/*
* inherit a event from parent task to child task:
*/