Patch "tracing: Stop current tracer when resizing buffer" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    tracing: Stop current tracer when resizing buffer

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tracing-stop-current-tracer-when-resizing-buffer.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 655a00cb0dbef586b2def7ce6eea039b8cb99163
Author: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Date:   Tue Dec 5 16:52:10 2023 -0500

    tracing: Stop current tracer when resizing buffer
    
    [ Upstream commit d78ab792705c7be1b91243b2544d1a79406a2ad7 ]
    
    When the ring buffer is being resized, it can cause side effects to the
    running tracer. For instance, there's a race with irqsoff tracer that
    swaps individual per cpu buffers between the main buffer and the snapshot
    buffer. The resize operation modifies the main buffer and then the
    snapshot buffer. If a swap happens in between those two operations it will
    break the tracer.
    
    Simply stop the running tracer before resizing the buffers and enable it
    again when finished.
    
    Link: https://lkml.kernel.org/r/20231205220010.748996423@xxxxxxxxxxx
    
    Cc: stable@xxxxxxxxxxxxxxx
    Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
    Cc: Mark Rutland <mark.rutland@xxxxxxx>
    Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
    Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
    Fixes: 3928a8a2d9808 ("ftrace: make work with new ring buffer")
    Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 049daa6a9ad42..657ecb8f03545 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6243,9 +6243,12 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
 	if (!tr->array_buffer.buffer)
 		return 0;
 
+	/* Do not allow tracing while resizng ring buffer */
+	tracing_stop_tr(tr);
+
 	ret = ring_buffer_resize(tr->array_buffer.buffer, size, cpu);
 	if (ret < 0)
-		return ret;
+		goto out_start;
 
 #ifdef CONFIG_TRACER_MAX_TRACE
 	if (!tr->current_trace->use_max_tr)
@@ -6273,7 +6276,7 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
 			WARN_ON(1);
 			tracing_disabled = 1;
 		}
-		return ret;
+		goto out_start;
 	}
 
 	update_buffer_entries(&tr->max_buffer, cpu);
@@ -6282,7 +6285,8 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
 #endif /* CONFIG_TRACER_MAX_TRACE */
 
 	update_buffer_entries(&tr->array_buffer, cpu);
-
+ out_start:
+	tracing_start_tr(tr);
 	return ret;
 }