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SubjectRe: [PATCHSET 00/17] perf tools: Introduce new 'ftrace' command (v4)
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Hi Jiri and Jeremy,

On Fri, 9 Aug 2013 12:23:06 +0200, Jiri Olsa wrote:
> On Tue, Jul 30, 2013 at 06:18:57PM +0900, Namhyung Kim wrote:
>> This patchset implements a front-end tool for kernel's ftrace. It
>> uses function_graph tracer by default and normal function tracer is
>> also supported. (Of course you need to enable those tracers in your
>> kernel first.)
>>
>> v4 changes:
>> * use pid instead of tid for -p option (David)
>> * not to poll() for reading ftrace pipes (Jiri)
>> * rename to create_perf_header() (Jiri)
>> * canonicalize directory name (Jiri)
>> * show more info when -D option was given (Jiri)
>> * update documentation (Jiri)
>> * and few more bug fixes
>>
>> I pushed it out to 'perf/ftrace-v4' branch on my tree at:
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
>
> got following for record:
>
> [root@dhcp-26-214 perf]# ./perf ftrace record kill
> usage: kill [ -s signal | -p ] [ -a ] pid ...
> kill -l [ signal ]
> recorder failed for some reason on cpu0
> recorder failed for some reason on cpu1

It seems like an empty trace pipe returns EAGAIN after child exited - I
expected an EOF. I don't know why I didn't meet this on my system (FYI
I'm running F17 and this patch tested on that kernel mostly). Maybe
recent kernel changed the behavior.

Anyway I added a check and printed error message on other cases. Could
you please test whether the patch below works?

>
>
> afterwards 'perf ftrace report' gets stuck with 2 processes:
>
> [jolsa@dhcp-26-214 perf]$ sudo pstack 1470
> #0 0x00007f23ab61e997 in munmap () from /lib64/libc.so.6
> #1 0x000000000047b5f7 in __perf_session__process_events ()
> #2 0x000000000043f230 in do_ftrace_report ()
> #3 0x0000000000440555 in cmd_ftrace ()
> #4 0x000000000041aad3 in run_builtin ()
> #5 0x000000000041a379 in main ()

Hmm.. this repeated munmap() calls are fixed also.


> [jolsa@dhcp-26-214 perf]$ sudo pstack 1471
> #0 0x00007f23ab61b623 in __select_nocancel () from /lib64/libc.so.6
> #1 0x000000000046a337 in pager_preexec ()
> #2 0x000000000045f5a3 in start_command ()
> #3 0x000000000046a4ab in setup_pager ()
> #4 0x0000000000440535 in cmd_ftrace ()
> #5 0x000000000041aad3 in run_builtin ()
> #6 0x000000000041a379 in main ()



------------8<-------------
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 9e78ec19caeb..10590b794cae 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -555,17 +555,25 @@ sleep:
while (true) {
int n = read(trace_fd, buf, sizeof(buf));

- if (n < 0)
- goto out_close;
- if (n == 0)
+ if (n < 0) {
+ if (errno == EINTR || errno == EAGAIN)
+ break;
+ perror("flush read");
+ goto out_close2;
+ } else if (n == 0)
break;
- if (write(output_fd, buf, n) != n)
- goto out_close;
+
+ if (write(output_fd, buf, n) != n) {
+ perror("flush write");
+ goto out_close2;
+ }

byte_written += n;
}
fra->state = RECORD_STATE__DONE;

+out_close2:
+ close(output_fd);
out_close:
close(trace_fd);
out:
@@ -579,6 +587,8 @@ out:
pthread_cond_signal(&recorder_ready_cond);
pthread_mutex_unlock(&recorder_mutex);
}
+
+ pr_debug2("done with %ld bytes\n", (long)byte_written);
return fra;
}

@@ -1139,12 +1149,12 @@ retry:
return record;
}

- munmap(fra->map, pevent_get_page_size(ftrace->pevent));
- fra->map = NULL;
-
if (fra->done)
return NULL;

+ munmap(fra->map, pevent_get_page_size(ftrace->pevent));
+ fra->map = NULL;
+
fra->offset += pevent_get_page_size(ftrace->pevent);
if (fra->offset >= fra->size) {
/* EOF */

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