On Tue, 12 Mar 2024 11:56:41 -0400
Steven Rostedt <rost...@goodmis.org> wrote:
> From: "Steven Rostedt (Google)" <rost...@goodmis.org>
>
> The rb_watermark_hit() checks if the amount of data in the ring buffer is
> above the percentage level passed in by the "full" variable. If it is, it
> returns true.
>
> But it also sets the "shortest_full" field of the cpu_buffer that informs
> writers that it needs to call the irq_work if the amount of data on the
> ring buffer is above the requested amount.
>
> The rb_watermark_hit() always sets the shortest_full even if the amount in
> the ring buffer is what it wants. As it is not going to wait, because it
> has what it wants, there's no reason to set shortest_full.
>
Yeah, it should avoid setting if !ret. Looks good to me.
Reviewed-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
Thank you,
> Cc: sta...@vger.kernel.org
> Fixes: 42fb0a1e84ff5 ("tracing/ring-buffer: Have polling block on watermark")
> Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org>
> ---
> kernel/trace/ring_buffer.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 9b887d44b8d9..350607cce869 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -834,9 +834,10 @@ static bool rb_watermark_hit(struct trace_buffer
> *buffer, int cpu, int full)
> pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
> ret = !pagebusy && full_hit(buffer, cpu, full);
>
> - if (!cpu_buffer->shortest_full ||
> - cpu_buffer->shortest_full > full)
> - cpu_buffer->shortest_full = full;
> + if (!ret && (!cpu_buffer->shortest_full ||
> + cpu_buffer->shortest_full > full)) {
> + cpu_buffer->shortest_full = full;
> + }
> raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
> }
> return ret;
> --
> 2.43.0
>
--
Masami Hiramatsu (Google) <mhira...@kernel.org>
