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Commit cc1f3573 authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google) Committed by Greg Kroah-Hartman
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ring-buffer: Have the shortest_full queue be the shortest not longest 

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: 2c2b0a78 ("ring-buffer: Add percentage of ring buffer full to wake up reader")
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 22707f03

kernel/trace/ring_buffer.c

+1 −1
Original line number Diff line number Diff line
@@ -662,7 +662,7 @@ int ring_buffer_wait(struct ring_buffer *buffer, int cpu, int full) 
			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 &&