[PATCH 1/2] tracing: Fix retry exhaustion in simple ring buffer reader swap
Ivan Immanuel Shaji via B4 Relay <[email protected]>
| Newsgroups | org.kernel.vger.stable,org.kernel.feeds.b4-sent,org.kernel.vger.linux-kernel,org.kernel.vger.linux-trace-kernel |
|---|---|
| Message-ID | <[email protected]> |
From: Ivan Immanuel Shaji <[email protected]> simple_ring_buffer_swap_reader_page() starts with retry set to 8 and post-decrements it only after a failed link replacement. On the final attempt, a successful replacement leaves retry at zero, while a failed replacement leaves it at -1. The current !retry test reverses both outcomes. It returns an error after a successful final replacement, leaving the link update complete but the reader bookkeeping unfinished. After a failed final replacement, it falls through and updates the head and reader pointers as though the replacement succeeded, which can corrupt the ring. Treat only a negative counter as exhaustion and return the documented -EBUSY error. Fixes: 34e5b958bdad ("tracing: Introduce simple_ring_buffer") Cc: [email protected] Assisted-by: LLM sparse Signed-off-by: Ivan Immanuel Shaji <[email protected]> --- kernel/trace/simple_ring_buffer.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/trace/simple_ring_buffer.c b/kernel/trace/simple_ring_buffer.c index f4642f5adda3..49913bb0057a 100644 --- a/kernel/trace/simple_ring_buffer.c +++ b/kernel/trace/simple_ring_buffer.c @@ -160,8 +160,8 @@ int simple_ring_buffer_swap_reader_page(struct simple_rb_per_cpu *cpu_buffer) overrun = cpu_buffer->meta->overrun; } while (!simple_bpage_unset_head_link(last, reader, SIMPLE_RB_LINK_NORMAL) && retry--); - if (!retry) - return -EINVAL; + if (retry < 0) + return -EBUSY; cpu_buffer->head_page = simple_bpage_from_link(reader->link.next); cpu_buffer->head_page->link.prev = &reader->link; -- 2.53.0