From: Ivan Immanuel Shaji <[email protected]>
The remote swap_reader_page callback can return -EBUSY when the writer
moves the head before the remote catches it, particularly during an event
storm on a small buffer. __rb_get_reader_page_from_remote() currently
warns about that failure but continues with the unchanged reader ID and
rearranges the local page list as though the swap succeeded.
Handle the callback failure as a recoverable error. Report it with
pr_warn_ratelimited() and return NULL. Callers already handle a NULL reader
page as a failed attempt. This avoids splicing the same page as both the
previous and new reader without flooding the log under contention.
Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes")
Cc: [email protected]
Assisted-by: LLM sparse
Signed-off-by: Ivan Immanuel Shaji <[email protected]>
---
kernel/trace/ring_buffer.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 3c3ed639923d..b0963ac6fd16 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -5805,8 +5805,11 @@ __rb_get_reader_page_from_remote(struct
ring_buffer_per_cpu *cpu_buffer)
prev_reader = cpu_buffer->subbuf_ids[cpu_buffer->meta_page->reader.id];
- WARN_ON_ONCE(cpu_buffer->remote->swap_reader_page(cpu_buffer->cpu,
-
cpu_buffer->remote->priv));
+ if (cpu_buffer->remote->swap_reader_page(cpu_buffer->cpu,
+ cpu_buffer->remote->priv)) {
+ pr_warn_ratelimited("Remote reader page swap failed\n");
+ return NULL;
+ }
/* nr_pages doesn't include the reader page */
if (WARN_ON_ONCE(cpu_buffer->meta_page->reader.id >
cpu_buffer->nr_pages))
return NULL;
--
2.53.0
