[PATCH] perf: detect when perf.data file not closed out properly

[PATCH] perf: detect when perf.data file not closed out properly

[David Ahern]

perf-record updates the header in the perf.data file at termination.
Without this update perf-report (and other processing builtins) cannot
properly read events from the file -- the algorithm in
__perf_session__process_events depends on the data_size which is read
from the file header and that function loops if data_size is 0.

Catch this condition when the file is opened and warn the user.

Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
---
 tools/perf/util/header.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 326068a..aa42c8c 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -2802,6 +2802,18 @@ int perf_session__read_header(struct perf_session *session, int fd)
 	if (perf_file_header__read(&f_header, header, fd) < 0)
 		return -EINVAL;
 
+	/*
+	 * sanity check that perf.data was written cleanly: data size
+	 * is initialized to 0 and updated only if the on_exit function
+	 * is run. If data size is still 0 then the file cannot be
+	 * processed.
+	 */
+	if (f_header.data.size == 0) {
+		pr_err("data size is 0. "
+		       "Was the record command properly terminated?\n");
+		return -1;
+	}
+
 	nr_attrs = f_header.attrs.size / f_header.attr_size;
 	lseek(fd, f_header.attrs.offset, SEEK_SET);
 
-- 
1.7.10.1

Re: [PATCH] perf: detect when perf.data file not closed out properly

[Ingo Molnar]

* David Ahern <dsahern@gmail.com> wrote:

> +		pr_err("data size is 0. "
> +		       "Was the record command properly terminated?\n");

Btw., a small stylistic request: please put user-visible strings into a 
single line - even if it technically turns into an overlong line.

		pr_err("data size is 0. Was the record command properly terminated?\n");

This 1) makes it easier for people to git grep the error text they are 
seeing during usage 2) makes it easier for _developers_ to see the 
messages they are outputing to users.

For example from the single-line output it's immediately visible that it 
should be capitalized thusly:

		pr_err("Data size is 0. Was the record command properly terminated?\n");

:-)

Thanks,

	Ingo

Re: [PATCH] perf: detect when perf.data file not closed out properly

[David Ahern]

On 5/9/13 3:32 AM, Ingo Molnar wrote:
>
> * David Ahern <dsahern@gmail.com> wrote:
>
>> +		pr_err("data size is 0. "
>> +		       "Was the record command properly terminated?\n");
>
> Btw., a small stylistic request: please put user-visible strings into a
> single line - even if it technically turns into an overlong line.
>
> 		pr_err("data size is 0. Was the record command properly terminated?\n");
>
> This 1) makes it easier for people to git grep the error text they are
> seeing during usage 2) makes it easier for _developers_ to see the
> messages they are outputing to users.

Totally agree just battling the line length.

>
> For example from the single-line output it's immediately visible that it
> should be capitalized thusly:
>
> 		pr_err("Data size is 0. Was the record command properly terminated?\n");
>

Ok. Will re-send later today.

David