[PATCH 1/2] perf: Add PERF_EVENT_IOC_INC_EVENT_LIMIT

[Charlie Jenkins]

PERF_EVENT_IOC_REFRESH immediately enables after incrementing
event_limit.  Provide a new ioctl flag that allows programs to increment
event_limit without enabling the event. A usecase for this is to set an
event_limit in combination with enable_on_exec.

Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
---
 include/linux/perf_event.h            |  4 ++--
 include/uapi/linux/perf_event.h       |  1 +
 kernel/events/core.c                  | 17 +++++++++++------
 tools/include/uapi/linux/perf_event.h |  1 +
 4 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index a5304ae8c654..40025a5eb98a 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1103,7 +1103,7 @@ extern int perf_event_task_enable(void);
 
 extern void perf_pmu_resched(struct pmu *pmu);
 
-extern int perf_event_refresh(struct perf_event *event, int refresh);
+extern int perf_event_refresh(struct perf_event *event, int refresh, bool enable);
 extern void perf_event_update_userpage(struct perf_event *event);
 extern int perf_event_release_kernel(struct perf_event *event);
 extern struct perf_event *
@@ -1770,7 +1770,7 @@ static inline int perf_event_read_local(struct perf_event *event, u64 *value,
 static inline void perf_event_print_debug(void)				{ }
 static inline int perf_event_task_disable(void)				{ return -EINVAL; }
 static inline int perf_event_task_enable(void)				{ return -EINVAL; }
-static inline int perf_event_refresh(struct perf_event *event, int refresh)
+static inline int perf_event_refresh(struct perf_event *event, int refresh, bool enable)
 {
 	return -EINVAL;
 }
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 3a64499b0f5d..992f51effb27 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -560,6 +560,7 @@ struct perf_event_query_bpf {
 #define PERF_EVENT_IOC_PAUSE_OUTPUT		_IOW('$', 9, __u32)
 #define PERF_EVENT_IOC_QUERY_BPF		_IOWR('$', 10, struct perf_event_query_bpf *)
 #define PERF_EVENT_IOC_MODIFY_ATTRIBUTES	_IOW('$', 11, struct perf_event_attr *)
+#define PERF_EVENT_IOC_INC_EVENT_LIMIT		_IO ('$', 12)
 
 enum perf_event_ioc_flags {
 	PERF_IOC_FLAG_GROUP		= 1U << 0,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 8f908f077935..b9d009733ace 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3142,7 +3142,7 @@ void perf_event_addr_filters_sync(struct perf_event *event)
 }
 EXPORT_SYMBOL_GPL(perf_event_addr_filters_sync);
 
-static int _perf_event_refresh(struct perf_event *event, int refresh)
+static int _perf_event_refresh(struct perf_event *event, int refresh, bool enable)
 {
 	/*
 	 * not supported on inherited events
@@ -3151,7 +3151,8 @@ static int _perf_event_refresh(struct perf_event *event, int refresh)
 		return -EINVAL;
 
 	atomic_add(refresh, &event->event_limit);
-	_perf_event_enable(event);
+	if (enable)
+		_perf_event_enable(event);
 
 	return 0;
 }
@@ -3159,13 +3160,13 @@ static int _perf_event_refresh(struct perf_event *event, int refresh)
 /*
  * See perf_event_disable()
  */
-int perf_event_refresh(struct perf_event *event, int refresh)
+int perf_event_refresh(struct perf_event *event, int refresh, bool enable)
 {
 	struct perf_event_context *ctx;
 	int ret;
 
 	ctx = perf_event_ctx_lock(event);
-	ret = _perf_event_refresh(event, refresh);
+	ret = _perf_event_refresh(event, refresh, enable);
 	perf_event_ctx_unlock(event, ctx);
 
 	return ret;
@@ -5920,7 +5921,7 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
 		break;
 
 	case PERF_EVENT_IOC_REFRESH:
-		return _perf_event_refresh(event, arg);
+		return _perf_event_refresh(event, arg, true);
 
 	case PERF_EVENT_IOC_PERIOD:
 	{
@@ -6006,6 +6007,10 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
 
 		return perf_event_modify_attr(event,  &new_attr);
 	}
+
+	case PERF_EVENT_IOC_INC_EVENT_LIMIT:
+		return _perf_event_refresh(event, arg, false);
+
 	default:
 		return -ENOTTY;
 	}
@@ -6721,7 +6726,7 @@ void perf_event_wakeup(struct perf_event *event)
 	ring_buffer_wakeup(event);
 
 	if (event->pending_kill) {
-		kill_fasync(perf_event_fasync(event), SIGIO, event->pending_kill);
+		kill_fasync(perf_event_fasync(event), SIGTRAP, event->pending_kill);
 		event->pending_kill = 0;
 	}
 }
diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index 3a64499b0f5d..992f51effb27 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -560,6 +560,7 @@ struct perf_event_query_bpf {
 #define PERF_EVENT_IOC_PAUSE_OUTPUT		_IOW('$', 9, __u32)
 #define PERF_EVENT_IOC_QUERY_BPF		_IOWR('$', 10, struct perf_event_query_bpf *)
 #define PERF_EVENT_IOC_MODIFY_ATTRIBUTES	_IOW('$', 11, struct perf_event_attr *)
+#define PERF_EVENT_IOC_INC_EVENT_LIMIT		_IO ('$', 12)
 
 enum perf_event_ioc_flags {
 	PERF_IOC_FLAG_GROUP		= 1U << 0,

-- 
2.44.0