linux-kernel - [PATCH] perf tools: Fix lockup using 32-bit compat vdso

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Date:	Tue,  7 Jul 2015 14:13:38 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	David Ahern <dsahern@...il.com>
Subject: [PATCH] perf tools: Fix lockup using 32-bit compat vdso

__machine__findnew_compat() is called only from
__machine__findnew_vdso_compat() which is called
only from machine__findnew_vdso() which already
holds machine->dsos.lock, so remove locking from
__machine__findnew_compat().

This manifests itself tracing 32-bit programs
with a 64-bit perf.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
---
 tools/perf/util/vdso.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/vdso.c b/tools/perf/util/vdso.c
index 4b89118f158d..44d440da15dc 100644
--- a/tools/perf/util/vdso.c
+++ b/tools/perf/util/vdso.c
@@ -236,18 +236,16 @@ static struct dso *__machine__findnew_compat(struct machine *machine,
 	const char *file_name;
 	struct dso *dso;
 
-	pthread_rwlock_wrlock(&machine->dsos.lock);
 	dso = __dsos__find(&machine->dsos, vdso_file->dso_name, true);
 	if (dso)
-		goto out_unlock;
+		goto out;
 
 	file_name = vdso__get_compat_file(vdso_file);
 	if (!file_name)
-		goto out_unlock;
+		goto out;
 
 	dso = __machine__addnew_vdso(machine, vdso_file->dso_name, file_name);
-out_unlock:
-	pthread_rwlock_unlock(&machine->dsos.lock);
+out:
 	return dso;
 }
 
-- 
1.9.1

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