ring-buffer: Do not die if rb_iter_peek() fails more than thrice (ff84c50c) · Commits · 戴 / test

kernel/trace/ring_buffer.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -4012,6 +4012,7 @@ rb_iter_peek(struct ring_buffer_iter iter, u64 ts)
		struct ring_buffer_per_cpu *cpu_buffer;
		struct ring_buffer_event *event;
		int nr_loops = 0;
		bool failed = false;

		if (ts)
		*ts = 0;
		@@ -4038,10 +4039,14 @@ rb_iter_peek(struct ring_buffer_iter iter, u64 ts)
		* to a data event, we should never loop more than three times.
		* Once for going to next page, once on time extend, and
		* finally once to get the event.
		* (We never hit the following condition more than thrice).
		* We should never hit the following condition more than thrice,
		* unless the buffer is very small, and there's a writer
		* that is causing the reader to fail getting an event.
		*/
		if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3))
		if (++nr_loops > 3) {
		RB_WARN_ON(cpu_buffer, !failed);
		return NULL;
		}

		if (rb_per_cpu_empty(cpu_buffer))
		return NULL;
		@@ -4052,8 +4057,10 @@ rb_iter_peek(struct ring_buffer_iter iter, u64 ts)
		}

		event = rb_iter_head_event(iter);
		if (!event)
		if (!event) {
		failed = true;
		goto again;
		}

		switch (event->type_len) {
		case RINGBUF_TYPE_PADDING: