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Message-ID: <20230822045937.3fc0da54@rorschach.local.home>
Date: Tue, 22 Aug 2023 04:59:37 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing: Fix to avoid wakeup loop in splice read of
per-cpu buffer
On Mon, 21 Aug 2023 23:19:18 +0900
"Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:
> if (!spd.nr_pages) {
> long wait_index;
> + size_t nr_pages;
> + size_t full;
size_t is usually considered "long" (machine word length).
>
> if (ret)
> goto out;
> @@ -8472,7 +8474,15 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
>
> wait_index = READ_ONCE(iter->wait_index);
>
> - ret = wait_on_pipe(iter, iter->tr->buffer_percent);
> + /* For splice, we have to ensure at least 1 page is filled */
> + nr_pages = ring_buffer_nr_pages(iter->array_buffer->buffer, iter->cpu_file);
> + if (nr_pages * iter->tr->buffer_percent < 100) {
> + full = nr_pages + 99;
> + do_div(full, nr_pages);
No need for do_div() as full is not 64 bit on 32 bit machines.
That's why the kernel test robot is complaining.
-- Steve
> + } else
> + full = iter->tr->buffer_percent;
> +
> + ret = wait_on_pipe(iter, full);
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