[PATCH v3 1/2] perf lock: Correct field name "flags"

[PATCH v3 1/2] perf lock: Correct field name "flags"

[Leo Yan]

The tracepoint "lock:lock_acquire" contains field "flags" but not
"flag".  Current code wrongly retrieves value from field "flag" and it
always gets zero for the value, thus "perf lock" doesn't report the
correct result.

This patch replaces the field name "flag" with "flags", so can read out
the correct flags for locking.

Fixes: e4cef1f65061 ("perf lock: Fix state machine to recognize lock sequence")
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
---
 tools/perf/builtin-lock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index f0a1dbacb46c..5cecc1ad78e1 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -406,7 +406,7 @@ static int report_lock_acquire_event(struct evsel *evsel,
 	struct lock_seq_stat *seq;
 	const char *name = evsel__strval(evsel, sample, "name");
 	u64 tmp	 = evsel__intval(evsel, sample, "lockdep_addr");
-	int flag = evsel__intval(evsel, sample, "flag");
+	int flag = evsel__intval(evsel, sample, "flags");
 
 	memcpy(&addr, &tmp, sizeof(void *));
 
-- 
2.17.1

[PATCH v3 2/2] perf lock: Don't free "lock_seq_stat" if read_count isn't zero

[Leo Yan]

When execute command "perf lock report", it hits failure and outputs log
as follows:

  perf: builtin-lock.c:623: report_lock_release_event: Assertion `!(seq->read_count < 0)' failed.
  Aborted

This is an imbalance issue.  The locking sequence structure
"lock_seq_stat" contains the reader counter and it is used to check if
the locking sequence is balance or not between acquiring and releasing.

If the tool wrongly frees "lock_seq_stat" when "read_count" isn't zero,
the "read_count" will be reset to zero when allocate a new structure at
the next time; thus it causes the wrong counting for reader and finally
results in imbalance issue.

To fix this issue, if detects "read_count" is not zero (means still
have read user in the locking sequence), goto the "end" tag to skip
freeing structure "lock_seq_stat".

Fixes: e4cef1f65061 ("perf lock: Fix state machine to recognize lock sequence")
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
---

v3: Corrected "Fixes" tag to reflect the first patch causing the issue
    (Jiri)

 tools/perf/builtin-lock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index 5cecc1ad78e1..a2f1e53f37a7 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -621,7 +621,7 @@ static int report_lock_release_event(struct evsel *evsel,
 	case SEQ_STATE_READ_ACQUIRED:
 		seq->read_count--;
 		BUG_ON(seq->read_count < 0);
-		if (!seq->read_count) {
+		if (seq->read_count) {
 			ls->nr_release++;
 			goto end;
 		}
-- 
2.17.1

Re: [PATCH v3 1/2] perf lock: Correct field name "flags"

[Arnaldo Carvalho de Melo]

Em Wed, Nov 04, 2020 at 05:42:28PM +0800, Leo Yan escreveu:
> The tracepoint "lock:lock_acquire" contains field "flags" but not
> "flag".  Current code wrongly retrieves value from field "flag" and it
> always gets zero for the value, thus "perf lock" doesn't report the
> correct result.
> 
> This patch replaces the field name "flag" with "flags", so can read out
> the correct flags for locking.


Thanks, applied both patches.

- Arnaldo

 
> Fixes: e4cef1f65061 ("perf lock: Fix state machine to recognize lock sequence")
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> Acked-by: Jiri Olsa <jolsa@redhat.com>
> ---
>  tools/perf/builtin-lock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
> index f0a1dbacb46c..5cecc1ad78e1 100644
> --- a/tools/perf/builtin-lock.c
> +++ b/tools/perf/builtin-lock.c
> @@ -406,7 +406,7 @@ static int report_lock_acquire_event(struct evsel *evsel,
>  	struct lock_seq_stat *seq;
>  	const char *name = evsel__strval(evsel, sample, "name");
>  	u64 tmp	 = evsel__intval(evsel, sample, "lockdep_addr");
> -	int flag = evsel__intval(evsel, sample, "flag");
> +	int flag = evsel__intval(evsel, sample, "flags");
>  
>  	memcpy(&addr, &tmp, sizeof(void *));
>  
> -- 
> 2.17.1
> 

-- 

- Arnaldo