linux-kernel - [PATCH 3.13 15/65] pkt_sched: fq: do not hold qdisc lock while allocating memory

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Message-Id: <20140411160959.783178615@linuxfoundation.org>
Date:	Fri, 11 Apr 2014 09:10:47 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.13 15/65] pkt_sched: fq: do not hold qdisc lock while allocating memory

3.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.com>

[ Upstream commit 2d8d40afd187bced0a3d056366fb58d66fe845e3 ]

Resizing fq hash table allocates memory while holding qdisc spinlock,
with BH disabled.

This is definitely not good, as allocation might sleep.

We can drop the lock and get it when needed, we hold RTNL so no other
changes can happen at the same time.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Fixes: afe4fd062416 ("pkt_sched: fq: Fair Queue packet scheduler")
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sched/sch_fq.c |   28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -578,9 +578,11 @@ static void fq_rehash(struct fq_sched_da
 	q->stat_gc_flows += fcnt;
 }
 
-static int fq_resize(struct fq_sched_data *q, u32 log)
+static int fq_resize(struct Qdisc *sch, u32 log)
 {
+	struct fq_sched_data *q = qdisc_priv(sch);
 	struct rb_root *array;
+	void *old_fq_root;
 	u32 idx;
 
 	if (q->fq_root && log == q->fq_trees_log)
@@ -593,13 +595,19 @@ static int fq_resize(struct fq_sched_dat
 	for (idx = 0; idx < (1U << log); idx++)
 		array[idx] = RB_ROOT;
 
-	if (q->fq_root) {
-		fq_rehash(q, q->fq_root, q->fq_trees_log, array, log);
-		kfree(q->fq_root);
-	}
+	sch_tree_lock(sch);
+
+	old_fq_root = q->fq_root;
+	if (old_fq_root)
+		fq_rehash(q, old_fq_root, q->fq_trees_log, array, log);
+
 	q->fq_root = array;
 	q->fq_trees_log = log;
 
+	sch_tree_unlock(sch);
+
+	kfree(old_fq_root);
+
 	return 0;
 }
 
@@ -675,9 +683,11 @@ static int fq_change(struct Qdisc *sch,
 		q->flow_refill_delay = usecs_to_jiffies(usecs_delay);
 	}
 
-	if (!err)
-		err = fq_resize(q, fq_log);
-
+	if (!err) {
+		sch_tree_unlock(sch);
+		err = fq_resize(sch, fq_log);
+		sch_tree_lock(sch);
+	}
 	while (sch->q.qlen > sch->limit) {
 		struct sk_buff *skb = fq_dequeue(sch);
 
@@ -723,7 +733,7 @@ static int fq_init(struct Qdisc *sch, st
 	if (opt)
 		err = fq_change(sch, opt);
 	else
-		err = fq_resize(q, q->fq_trees_log);
+		err = fq_resize(sch, q->fq_trees_log);
 
 	return err;
 }


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