* [PATCH] ring-buffer: Fix reader page read offset for remote buffers
@ 2026-07-29 13:36 Vincent Donnefort
2026-07-29 13:43 ` Keir Fraser
0 siblings, 1 reply; 2+ messages in thread
From: Vincent Donnefort @ 2026-07-29 13:36 UTC (permalink / raw)
To: rostedt, mhiramat, linux-trace-kernel
Cc: mathieu.desnoyers, kernel-team, linux-kernel, keirf,
Vincent Donnefort
A page swapped in by __rb_get_reader_page_from_remote() retains its
stale read offset, causing subsequent reads to skip events or read
past valid data. Fix it.
Fixes: fbd1743ecba1 ("ring-buffer: Add non-consuming read for ring-buffer remotes")
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 804ccae694d2..78d3875a47a5 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -5783,6 +5783,7 @@ __rb_get_reader_page_from_remote(struct ring_buffer_per_cpu *cpu_buffer)
cpu_buffer->head_page = new_head;
cpu_buffer->reader_page = new_reader;
+ cpu_buffer->reader_page->read = 0;
cpu_buffer->pages = &new_head->list;
cpu_buffer->read_stamp = new_reader->page->time_stamp;
cpu_buffer->lost_events = cpu_buffer->meta_page->reader.lost_events;
base-commit: f5098b6bae761e346ebcd9da7f95622c04733cff
--
2.55.0.487.gaf234c4eb3-goog
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] ring-buffer: Fix reader page read offset for remote buffers
2026-07-29 13:36 [PATCH] ring-buffer: Fix reader page read offset for remote buffers Vincent Donnefort
@ 2026-07-29 13:43 ` Keir Fraser
0 siblings, 0 replies; 2+ messages in thread
From: Keir Fraser @ 2026-07-29 13:43 UTC (permalink / raw)
To: Vincent Donnefort
Cc: rostedt, mhiramat, linux-trace-kernel, mathieu.desnoyers,
kernel-team, linux-kernel
On Wed, Jul 29, 2026 at 02:36:09PM +0100, Vincent Donnefort wrote:
> A page swapped in by __rb_get_reader_page_from_remote() retains its
> stale read offset, causing subsequent reads to skip events or read
> past valid data. Fix it.
>
> Fixes: fbd1743ecba1 ("ring-buffer: Add non-consuming read for ring-buffer remotes")
> Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Reviewed-by: Keir Fraser <keirf@google.com>
Tested-by: Keir Fraser <keirf@google.com>
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 804ccae694d2..78d3875a47a5 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -5783,6 +5783,7 @@ __rb_get_reader_page_from_remote(struct ring_buffer_per_cpu *cpu_buffer)
>
> cpu_buffer->head_page = new_head;
> cpu_buffer->reader_page = new_reader;
> + cpu_buffer->reader_page->read = 0;
> cpu_buffer->pages = &new_head->list;
> cpu_buffer->read_stamp = new_reader->page->time_stamp;
> cpu_buffer->lost_events = cpu_buffer->meta_page->reader.lost_events;
>
> base-commit: f5098b6bae761e346ebcd9da7f95622c04733cff
> --
> 2.55.0.487.gaf234c4eb3-goog
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2026-07-29 13:36 [PATCH] ring-buffer: Fix reader page read offset for remote buffers Vincent Donnefort
2026-07-29 13:43 ` Keir Fraser
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