linux-kernel - Re: [PATCH 1/1] tracing/boot: Add ftrace.instance.*.alloc

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Message-ID: <20201012111140.5e8e2e0c@gandalf.local.home>
Date:   Mon, 12 Oct 2020 11:11:40 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Tom Zanussi <zanussi@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] tracing/boot: Add ftrace.instance.*.alloc_snapshot
 option

On Sun, 11 Oct 2020 00:28:09 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> Add ftrace.instance.*.alloc_snapshot option.
> 
> This option has been described in Documentation/trace/boottime-trace.rst
> but not implemented yet.
> 
> ftrace.[instance.INSTANCE.]alloc_snapshot
>    Allocate snapshot buffer.
> 
> The difference from kernel.alloc_snapshot is that the kernel.alloc_snapshot
> will allocate the buffer only for the main instance, but this can allocate
> buffer for any new instances.

I queued this up. Thanks Masami!

-- Steve

> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  kernel/trace/trace_boot.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
> index 754e3cf2df3a..c22a152ef0b4 100644
> --- a/kernel/trace/trace_boot.c
> +++ b/kernel/trace/trace_boot.c
> @@ -284,6 +284,12 @@ trace_boot_enable_tracer(struct trace_array *tr, struct xbc_node *node)
>  		if (tracing_set_tracer(tr, p) < 0)
>  			pr_err("Failed to set given tracer: %s\n", p);
>  	}
> +
> +	/* Since tracer can free snapshot buffer, allocate snapshot here.*/
> +	if (xbc_node_find_value(node, "alloc_snapshot", NULL)) {
> +		if (tracing_alloc_snapshot_instance(tr) < 0)
> +			pr_err("Failed to allocate snapshot buffer\n");
> +	}
>  }
>  
>  static void __init