From: Steven Rostedt (Google) rostedt@goodmis.org
commit 3b19d614b61b93a131f463817e08219c9ce1fee3 upstream.
The logic to know when the shortest waiters on the ring buffer should be woken up or not has uses a less than instead of a greater than compare, which causes the shortest_full to actually be the longest.
Link: https://lkml.kernel.org/r/20220927231823.718039222@goodmis.org
Cc: stable@vger.kernel.org Cc: Ingo Molnar mingo@kernel.org Cc: Andrew Morton akpm@linux-foundation.org Fixes: 2c2b0a78b3739 ("ring-buffer: Add percentage of ring buffer full to wake up reader") Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/ring_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -888,7 +888,7 @@ int ring_buffer_wait(struct trace_buffer nr_pages = cpu_buffer->nr_pages; dirty = ring_buffer_nr_dirty_pages(buffer, cpu); if (!cpu_buffer->shortest_full || - cpu_buffer->shortest_full < full) + cpu_buffer->shortest_full > full) cpu_buffer->shortest_full = full; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); if (!pagebusy &&