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Date: Wed, 11 Jul 2007 16:41:37 +0300
From: Ranko Zivojnovic <ranko@...dernet.net>
To: netdev@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Patrick McHardy <kaber@...sh.net>,
Jarek Poplawski <jarkao2@...pl>
Subject: [NET]: gen_estimator deadlock fix
Fixes ABBA deadlock noted by Patrick McHardy <kaber@...sh.net>:
> There is at least one ABBA deadlock, est_timer() does:
> read_lock(&est_lock)
> spin_lock(e->stats_lock) (which is dev->queue_lock)
>
> and qdisc_destroy calls htb_destroy under dev->queue_lock, which
> calls htb_destroy_class, then gen_kill_estimator and this
> write_locks est_lock.
est_lock completely removed and the RCU list implemented instead.
Both gen_kill_estimator and gen_new_estimator are already called under
rtnl_mutex.
Signed-off-by: Ranko Zivojnovic <ranko@...dernet.net>
---
net/core/gen_estimator.c | 73 ++++++++++++++++++++++++----------------------
1 files changed, 38 insertions(+), 35 deletions(-)
diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c
index cc84d8d..444b2bd 100644
--- a/net/core/gen_estimator.c
+++ b/net/core/gen_estimator.c
@@ -79,7 +79,7 @@
struct gen_estimator
{
- struct gen_estimator *next;
+ struct list_head list;
struct gnet_stats_basic *bstats;
struct gnet_stats_rate_est *rate_est;
spinlock_t *stats_lock;
@@ -89,26 +89,24 @@ struct gen_estimator
u32 last_packets;
u32 avpps;
u32 avbps;
+ struct rcu_head e_rcu;
};
struct gen_estimator_head
{
struct timer_list timer;
- struct gen_estimator *list;
+ struct list_head list;
};
static struct gen_estimator_head elist[EST_MAX_INTERVAL+1];
-/* Estimator array lock */
-static DEFINE_RWLOCK(est_lock);
-
static void est_timer(unsigned long arg)
{
int idx = (int)arg;
struct gen_estimator *e;
- read_lock(&est_lock);
- for (e = elist[idx].list; e; e = e->next) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(e, &elist[idx].list, list) {
u64 nbytes;
u32 npackets;
u32 rate;
@@ -128,9 +126,9 @@ static void est_timer(unsigned long arg)
spin_unlock(e->stats_lock);
}
- if (elist[idx].list != NULL)
+ if (!list_empty(&elist[idx].list))
mod_timer(&elist[idx].timer, jiffies + ((HZ<<idx)/4));
- read_unlock(&est_lock);
+ rcu_read_unlock();
}
/**
@@ -147,12 +145,15 @@ static void est_timer(unsigned long arg)
* &rate_est with the statistics lock grabed during this period.
*
* Returns 0 on success or a negative error code.
+ *
+ * NOTE: Called under rtnl_mutex
*/
int gen_new_estimator(struct gnet_stats_basic *bstats,
struct gnet_stats_rate_est *rate_est, spinlock_t *stats_lock, struct rtattr *opt)
{
struct gen_estimator *est;
struct gnet_estimator *parm = RTA_DATA(opt);
+ int idx;
if (RTA_PAYLOAD(opt) < sizeof(*parm))
return -EINVAL;
@@ -164,7 +165,7 @@ int gen_new_estimator(struct gnet_stats_basic *bstats,
if (est == NULL)
return -ENOBUFS;
- est->interval = parm->interval + 2;
+ est->interval = idx = parm->interval + 2;
est->bstats = bstats;
est->rate_est = rate_est;
est->stats_lock = stats_lock;
@@ -174,20 +175,25 @@ int gen_new_estimator(struct gnet_stats_basic *bstats,
est->last_packets = bstats->packets;
est->avpps = rate_est->pps<<10;
- est->next = elist[est->interval].list;
- if (est->next == NULL) {
- init_timer(&elist[est->interval].timer);
- elist[est->interval].timer.data = est->interval;
- elist[est->interval].timer.expires = jiffies + ((HZ<<est->interval)/4);
- elist[est->interval].timer.function = est_timer;
- add_timer(&elist[est->interval].timer);
+ if (!elist[idx].timer.function) {
+ INIT_LIST_HEAD(&elist[idx].list);
+ setup_timer(&elist[idx].timer, est_timer, est->interval);
}
- write_lock_bh(&est_lock);
- elist[est->interval].list = est;
- write_unlock_bh(&est_lock);
+
+ if (list_empty(&elist[idx].list))
+ mod_timer(&elist[idx].timer, jiffies + ((HZ<<idx)/4));
+
+ list_add_rcu(&est->list, &elist[idx].list);
return 0;
}
+static void __gen_kill_estimator(struct rcu_head *head)
+{
+ struct gen_estimator *e = container_of(head,
+ struct gen_estimator, e_rcu);
+ kfree(e);
+}
+
/**
* gen_kill_estimator - remove a rate estimator
* @bstats: basic statistics
@@ -195,31 +201,28 @@ int gen_new_estimator(struct gnet_stats_basic *bstats,
*
* Removes the rate estimator specified by &bstats and &rate_est
* and deletes the timer.
+ *
+ * NOTE: Called under rtnl_mutex
*/
void gen_kill_estimator(struct gnet_stats_basic *bstats,
struct gnet_stats_rate_est *rate_est)
{
int idx;
- struct gen_estimator *est, **pest;
+ struct gen_estimator *e, *n;
for (idx=0; idx <= EST_MAX_INTERVAL; idx++) {
- int killed = 0;
- pest = &elist[idx].list;
- while ((est=*pest) != NULL) {
- if (est->rate_est != rate_est || est->bstats != bstats) {
- pest = &est->next;
- continue;
- }
- write_lock_bh(&est_lock);
- *pest = est->next;
- write_unlock_bh(&est_lock);
+ /* Skip non initialized indexes */
+ if (!elist[idx].timer.function)
+ continue;
+
+ list_for_each_entry_safe(e, n, &elist[idx].list, list) {
+ if (e->rate_est != rate_est || e->bstats != bstats)
+ continue;
- kfree(est);
- killed++;
+ list_del_rcu(&e->list);
+ call_rcu(&e->e_rcu, __gen_kill_estimator);
}
- if (killed && elist[idx].list == NULL)
- del_timer(&elist[idx].timer);
}
}
-
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