linux-kernel - [RFC][PATCH 03/10] taskstats: Split fill

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Date:	Thu, 23 Sep 2010 16:01:07 +0200
From:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
To:	Shailabh Nagar <nagar1234@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	John stultz <johnstul@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Oleg Nesterov <oleg@...hat.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Cc:	linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC][PATCH 03/10] taskstats: Split fill_pid function

Subject: [PATCH] taskstats: Split fill_pid function

From: Michael Holzheu <holzheu@...ux.vnet.ibm.com>

Separate the finding of a task_struct by pid or tgid from filling the taskstats
data. This makes the code more readable.

Signed-off-by: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
---
 kernel/taskstats.c |   50 +++++++++++++++++++++-----------------------------
 1 file changed, 21 insertions(+), 29 deletions(-)

--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -175,22 +175,8 @@ static void send_cpu_listeners(struct sk
 	up_write(&listeners->sem);
 }
 
-static int fill_pid(pid_t pid, struct task_struct *tsk,
-		struct taskstats *stats)
+static void fill_stats(struct task_struct *tsk, struct taskstats *stats)
 {
-	int rc = 0;
-
-	if (!tsk) {
-		rcu_read_lock();
-		tsk = find_task_by_vpid(pid);
-		if (tsk)
-			get_task_struct(tsk);
-		rcu_read_unlock();
-		if (!tsk)
-			return -ESRCH;
-	} else
-		get_task_struct(tsk);
-
 	memset(stats, 0, sizeof(*stats));
 	/*
 	 * Each accounting subsystem adds calls to its functions to
@@ -209,17 +195,27 @@ static int fill_pid(pid_t pid, struct ta
 
 	/* fill in extended acct fields */
 	xacct_add_tsk(stats, tsk);
+}
 
-	/* Define err: label here if needed */
-	put_task_struct(tsk);
-	return rc;
+static int fill_stats_for_pid(pid_t pid, struct taskstats *stats)
+{
+	struct task_struct *tsk;
 
+	rcu_read_lock();
+	tsk = find_task_by_vpid(pid);
+	if (tsk)
+		get_task_struct(tsk);
+	rcu_read_unlock();
+	if (!tsk)
+		return -ESRCH;
+	fill_stats(tsk, stats);
+	put_task_struct(tsk);
+	return 0;
 }
 
-static int fill_tgid(pid_t tgid, struct task_struct *first,
-		struct taskstats *stats)
+static int fill_stats_for_tgid(pid_t tgid, struct taskstats *stats)
 {
-	struct task_struct *tsk;
+	struct task_struct *tsk, *first;
 	unsigned long flags;
 	int rc = -ESRCH;
 
@@ -228,8 +224,7 @@ static int fill_tgid(pid_t tgid, struct 
 	 * leaders who are already counted with the dead tasks
 	 */
 	rcu_read_lock();
-	if (!first)
-		first = find_task_by_vpid(tgid);
+	first = find_task_by_vpid(tgid);
 
 	if (!first || !lock_task_sighand(first, &flags))
 		goto out;
@@ -268,7 +263,6 @@ out:
 	return rc;
 }
 
-
 static void fill_tgid_exit(struct task_struct *tsk)
 {
 	unsigned long flags;
@@ -477,7 +471,7 @@ static int cmd_attr_pid(struct genl_info
 	if (!stats)
 		goto err;
 
-	rc = fill_pid(pid, NULL, stats);
+	rc = fill_stats_for_pid(pid, stats);
 	if (rc < 0)
 		goto err;
 	return send_reply(rep_skb, info);
@@ -507,7 +501,7 @@ static int cmd_attr_tgid(struct genl_inf
 	if (!stats)
 		goto err;
 
-	rc = fill_tgid(tgid, NULL, stats);
+	rc = fill_stats_for_tgid(tgid, stats);
 	if (rc < 0)
 		goto err;
 	return send_reply(rep_skb, info);
@@ -593,9 +587,7 @@ void taskstats_exit(struct task_struct *
 	if (!stats)
 		goto err;
 
-	rc = fill_pid(-1, tsk, stats);
-	if (rc < 0)
-		goto err;
+	fill_stats(tsk, stats);
 
 	/*
 	 * Doesn't matter if tsk is the leader or the last group member leaving


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