linux-kernel - Re: [PATCH 5/9] perf util: Handle failure case in trace

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Date:	Tue, 19 Mar 2013 10:47:53 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 5/9] perf util: Handle failure case in trace_report()

On Tue, 2013-03-19 at 17:53 +0900, Namhyung Kim wrote:

> @@ -3100,7 +3105,7 @@ int perf_event__process_tracing_data(union perf_event *event,
>  		}
>  	}
>  
> -	if (size_read + padding != size) {
> +	if (size_read + padding != size || session->pevent == NULL) {
>  		pr_err("%s: tracing data size mismatch", __func__);

This is a strange error to give when pevent is NULL. Could have been a
malloc failure.


>  		return -1;
>  	}
> diff --git a/tools/perf/util/trace-event-read.c b/tools/perf/util/trace-event-read.c
> index 7cb24635adf2..129362b97ca5 100644
> --- a/tools/perf/util/trace-event-read.c
> +++ b/tools/perf/util/trace-event-read.c
> @@ -293,7 +293,10 @@ ssize_t trace_report(int fd, struct pevent **ppevent, bool __repipe)
>  	int show_version = 0;
>  	int show_funcs = 0;
>  	int show_printk = 0;
> -	ssize_t size;
> +	ssize_t size = -1;
> +	struct pevent *pevent;
> +
> +	*ppevent = NULL;
>  
>  	calc_data_size = 1;
>  	repipe = __repipe;
> @@ -317,34 +320,38 @@ ssize_t trace_report(int fd, struct pevent **ppevent, bool __repipe)
>  	file_bigendian = buf[0];
>  	host_bigendian = bigendian();
>  
> -	*ppevent = read_trace_init(file_bigendian, host_bigendian);
> -	if (*ppevent == NULL)
> -		die("read_trace_init failed");
> +	pevent = read_trace_init(file_bigendian, host_bigendian);
> +	if (pevent == NULL) {

Shouldn't we still set *ppevent to NULL? Or will the user now need to
make sure that its pevent is NULL and always check for error?

-- Steve


> +		pr_err("read_trace_init failed");
> +		goto out;
> +	}
>  
>  	read_or_die(buf, 1);
>  	long_size = buf[0];
>  
> -	page_size = read4(*ppevent);
> -
> -	read_header_files(*ppevent);
> +	page_size = read4(pevent);
>  
> -	read_ftrace_files(*ppevent);
> -	read_event_files(*ppevent);
> -	read_proc_kallsyms(*ppevent);
> -	read_ftrace_printk(*ppevent);
> +	read_header_files(pevent);
> +	read_ftrace_files(pevent);
> +	read_event_files(pevent);
> +	read_proc_kallsyms(pevent);
> +	read_ftrace_printk(pevent);
>  
>  	size = calc_data_size - 1;
>  	calc_data_size = 0;
>  	repipe = false;
>  
>  	if (show_funcs) {
> -		pevent_print_funcs(*ppevent);
> -		return size;
> -	}
> -	if (show_printk) {
> -		pevent_print_printk(*ppevent);
> -		return size;
> +		pevent_print_funcs(pevent);
> +	} else if (show_printk) {
> +		pevent_print_printk(pevent);
>  	}
>  
> +	*ppevent = pevent;
> +	pevent = NULL;
> +
> +out:
> +	if (pevent)
> +		pevent_free(pevent);
>  	return size;
>  }


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