[tip: perf/core] perf: Apply PERF_EVENT_IOC_MODIFY_ATTRIBUTES to children

[tip-bot2 for Marco Elver]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     47f661eca0700928012e11c57ea0328f5ccfc3b9
Gitweb:        https://git.kernel.org/tip/47f661eca0700928012e11c57ea0328f5ccfc3b9
Author:        Marco Elver <elver@xxxxxxxxxx>
AuthorDate:    Thu, 08 Apr 2021 12:35:57 +02:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 16 Apr 2021 16:32:40 +02:00

perf: Apply PERF_EVENT_IOC_MODIFY_ATTRIBUTES to children

As with other ioctls (such as PERF_EVENT_IOC_{ENABLE,DISABLE}), fix up
handling of PERF_EVENT_IOC_MODIFY_ATTRIBUTES to also apply to children.

Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20210408103605.1676875-3-elver@xxxxxxxxxx
---
 kernel/events/core.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 318ff7b..10ed2cd 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3200,16 +3200,36 @@ static int perf_event_modify_breakpoint(struct perf_event *bp,
 static int perf_event_modify_attr(struct perf_event *event,
 				  struct perf_event_attr *attr)
 {
+	int (*func)(struct perf_event *, struct perf_event_attr *);
+	struct perf_event *child;
+	int err;
+
 	if (event->attr.type != attr->type)
 		return -EINVAL;
 
 	switch (event->attr.type) {
 	case PERF_TYPE_BREAKPOINT:
-		return perf_event_modify_breakpoint(event, attr);
+		func = perf_event_modify_breakpoint;
+		break;
 	default:
 		/* Place holder for future additions. */
 		return -EOPNOTSUPP;
 	}
+
+	WARN_ON_ONCE(event->ctx->parent_ctx);
+
+	mutex_lock(&event->child_mutex);
+	err = func(event, attr);
+	if (err)
+		goto out;
+	list_for_each_entry(child, &event->child_list, child_list) {
+		err = func(child, attr);
+		if (err)
+			goto out;
+	}
+out:
+	mutex_unlock(&event->child_mutex);
+	return err;
 }
 
 static void ctx_sched_out(struct perf_event_context *ctx,