linux-kernel - Re: [PATCH] tracing: Have trace_marker break up by lines by size of trace

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Message-Id: <20231213091933.e3c78e210683b75b9dcbf59f@kernel.org>
Date:   Wed, 13 Dec 2023 09:19:33 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH] tracing: Have trace_marker break up by lines by size of
 trace_seq

On Tue, 12 Dec 2023 19:04:22 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
> 
> If a trace_marker write is bigger than what trace_seq can hold, then it
> will print "LINE TOO BIG" message and not what was written.
> 
> Instead, if check if the write is bigger than the trace_seq and break it

Instead, check if ... ?

> up by that size.
> 
> Ideally, we could make the trace_seq dynamic that could hold this. But
> that's for another time.

I think this is OK, but if possible it is better to be merged with the
"LINE TOO BIG" patch (by updating the version).

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thank you,

> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> ---
>  kernel/trace/trace.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 893e749713d3..2a21bc840fe7 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -7298,6 +7298,11 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
>  	if (cnt < FAULTED_SIZE)
>  		size += FAULTED_SIZE - cnt;
>  
> +	if (size > TRACE_SEQ_BUFFER_SIZE) {
> +		cnt -= size - TRACE_SEQ_BUFFER_SIZE;
> +		goto again;
> +	}
> +
>  	buffer = tr->array_buffer.buffer;
>  	event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
>  					    tracing_gen_ctx());
> -- 
> 2.42.0
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>