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Message-Id: <20201021003948.28817-2-leo.yan@linaro.org>
Date: Wed, 21 Oct 2020 08:39:48 +0800
From: Leo Yan <leo.yan@...aro.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Hitoshi Mitake <mitake@....info.waseda.ac.jp>,
Frederic Weisbecker <fweisbec@...il.com>,
linux-kernel@...r.kernel.org
Cc: Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v2 2/2] perf lock: Don't free "lock_seq_stat" if read_count isn't zero
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@...aro.org>
---
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
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