linux-kernel - [PATCH] perf_event: mount debugfs automatically

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Message-ID: <4B383DE3.3070702@cn.fujitsu.com>
Date:	Mon, 28 Dec 2009 13:10:59 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Paul Mackerras <paulus@...ba.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] perf_event: mount debugfs automatically

Mount debugfs automatically if it's not mounted, umount it
when programme exit

Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
---
 tools/perf/perf.c         |   10 +++++++++-
 tools/perf/util/debugfs.c |   16 +++++++---------
 tools/perf/util/debugfs.h |    2 +-
 3 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 873e55f..ee84fc1 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -388,7 +388,7 @@ static int run_argv(int *argcp, const char ***argv)
 /* mini /proc/mounts parser: searching for "^blah /mount/point debugfs" */
 static void get_debugfs_mntpt(void)
 {
-	const char *path = debugfs_find_mountpoint();
+	const char *path = debugfs_mount(NULL);
 
 	if (path)
 		strncpy(debugfs_mntpt, path, sizeof(debugfs_mntpt));
@@ -396,6 +396,11 @@ static void get_debugfs_mntpt(void)
 		debugfs_mntpt[0] = '\0';
 }
 
+static void umount_debugfs(void)
+{
+	debugfs_umount();
+}
+
 int main(int argc, const char **argv)
 {
 	const char *cmd;
@@ -405,6 +410,9 @@ int main(int argc, const char **argv)
 		cmd = "perf-help";
 	/* get debugfs mount point from /proc/mounts */
 	get_debugfs_mntpt();
+
+	atexit(umount_debugfs);
+
 	/*
 	 * "perf-xxxx" is the same as "perf xxxx", but we obviously:
 	 *
diff --git a/tools/perf/util/debugfs.c b/tools/perf/util/debugfs.c
index 06b73ee..1f805fd 100644
--- a/tools/perf/util/debugfs.c
+++ b/tools/perf/util/debugfs.c
@@ -106,16 +106,14 @@ int debugfs_valid_entry(const char *path)
 	return 0;
 }
 
-/* mount the debugfs somewhere */
+/* mount the debugfs somewhere if it's not mounted */
 
-int debugfs_mount(const char *mountpoint)
+char *debugfs_mount(const char *mountpoint)
 {
-	char mountcmd[128];
-
 	/* see if it's already mounted */
 	if (debugfs_find_mountpoint()) {
 		debugfs_premounted = 1;
-		return 0;
+		return debugfs_mountpoint;
 	}
 
 	/* if not mounted and no argument */
@@ -127,13 +125,13 @@ int debugfs_mount(const char *mountpoint)
 			mountpoint = "/sys/kernel/debug";
 	}
 
+	if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
+		return NULL;
+
 	/* save the mountpoint */
 	strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
 
-	/* mount it */
-	snprintf(mountcmd, sizeof(mountcmd),
-		 "/bin/mount -t debugfs debugfs %s", mountpoint);
-	return system(mountcmd);
+	return debugfs_mountpoint;
 }
 
 /* umount the debugfs */
diff --git a/tools/perf/util/debugfs.h b/tools/perf/util/debugfs.h
index 3cd14f9..83a0287 100644
--- a/tools/perf/util/debugfs.h
+++ b/tools/perf/util/debugfs.h
@@ -15,7 +15,7 @@
 extern const char *debugfs_find_mountpoint(void);
 extern int debugfs_valid_mountpoint(const char *debugfs);
 extern int debugfs_valid_entry(const char *path);
-extern int debugfs_mount(const char *mountpoint);
+extern char *debugfs_mount(const char *mountpoint);
 extern int debugfs_umount(void);
 extern int debugfs_write(const char *entry, const char *value);
 extern int debugfs_read(const char *entry, char *buffer, size_t size);
-- 
1.6.1.2


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