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Date:   Tue, 23 Feb 2021 15:34:23 +0100
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Subject: [PATCH RFC 1/4] perf/core: Apply PERF_EVENT_IOC_MODIFY_ATTRIBUTES to children
From:   Marco Elver <elver@google.com>
To:     elver@google.com, peterz@infradead.org,
        alexander.shishkin@linux.intel.com, acme@kernel.org,
        mingo@redhat.com, jolsa@redhat.com, mark.rutland@arm.com,
        namhyung@kernel.org, tglx@linutronix.de
Cc:     glider@google.com, viro@zeniv.linux.org.uk, arnd@arndb.de,
        christian@brauner.io, dvyukov@google.com, jannh@google.com,
        axboe@kernel.dk, mascasa@google.com, pcc@google.com,
        irogers@google.com, kasan-dev@googlegroups.com,
        linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-m68k@lists.linux-m68k.org,
        x86@kernel.org
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Precedence: bulk

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.

Link: https://lkml.kernel.org/r/YBqVaY8aTMYtoUnX@hirez.programming.kicks-ass.net
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Marco Elver <elver@google.com>
---
 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 129dee540a8b..37a8297be164 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3179,16 +3179,36 @@ 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,
-- 
2.30.0.617.g56c4b15f3c-goog