linux-kernel - Re: [PATCH 06/10] perf report: Setup browser if stdout is a pipe

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Date:	Tue, 6 Dec 2011 11:29:10 -0200
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Tom Zanussi <tzanussi@...il.com>
Cc:	Robert Richter <robert.richter@....com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/10] perf report: Setup browser if stdout is a pipe

Em Tue, Dec 06, 2011 at 11:32:36AM +0100, Robert Richter escreveu:
> The decision to setup the browser should be made if stdout is pipe,
> not stdin.

I can't remember what made that logic be like that...  Here it is:

commit 46656ac7fb3252f8a3db29b18638e0e8067849ba
Author: Tom Zanussi <tzanussi@...il.com>
Date:   Thu Apr 1 23:59:17 2010 -0500

    perf report: Introduce special handling for pipe input
    
    Adds special treatment for stdin - if the user specifies '-i -'
    to perf report, the intent is that the event stream be written
    to stdin rather than from a disk file.
    
    The actual handling of the '-' filename is done by the session;
    this just adds a signal handler to stop reporting, and turns off
    interference by the pager.
    
    Signed-off-by: Tom Zanussi <tzanussi@...il.com>
    Acked-by: Thomas Gleixner <tglx@...utronix.de>
    Cc: fweisbec@...il.com
    Cc: rostedt@...dmis.org
    Cc: k-keiichi@...jp.nec.com
    Cc: acme@...stprotocols.net
    LKML-Reference: <1270184365-8281-4-git-send-email-tzanussi@...il.com>
    Signed-off-by: Ingo Molnar <mingo@...e.hu>


I can't understand the comment either, as I think it should've read "the
intent is that the event stream be _read from stdin_ rather than from a
disk file."

And I don't know what would be the pager interference there.

Tom, could you elaborate on this?

Thanks,

- Arnaldo
    
 
> Signed-off-by: Robert Richter <robert.richter@....com>
> ---
>  tools/perf/builtin-report.c |    9 ++++++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
> index 4d7c834..88ca2d4 100644
> --- a/tools/perf/builtin-report.c
> +++ b/tools/perf/builtin-report.c
> @@ -504,6 +504,8 @@ static const struct option options[] = {
>  
>  int cmd_report(int argc, const char **argv, const char *prefix __used)
>  {
> +	struct stat st;
> +
>  	argc = parse_options(argc, argv, options, report_usage, 0);
>  
>  	if (use_stdio)
> @@ -514,10 +516,11 @@ int cmd_report(int argc, const char **argv, const char *prefix __used)
>  	if (inverted_callchain)
>  		callchain_param.order = ORDER_CALLER;
>  
> -	if (strcmp(input_name, "-") != 0)
> -		setup_browser(true);
> -	else
> +	if (!fstat(STDOUT_FILENO, &st) && S_ISFIFO(st.st_mode))
>  		use_browser = 0;
> +	else
> +		setup_browser(true);
> +
>  	/*
>  	 * Only in the newt browser we are doing integrated annotation,
>  	 * so don't allocate extra space that won't be used in the stdio
> -- 
> 1.7.7
> 
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