On Mon, 2007-07-09 at 15:52 +0200, Patrick McHardy wrote:
> Ranko Zivojnovic wrote:
> > Patrick, I've taken liberty to try and implement this myself. Attached
> > is the whole new gen_estimator-fix-locking-and-timer-related-bugs.patch
> > that is RCU lists based. Please be kind to review.
>
> Thanks for taking care of this, I'm a bit behind.
Glad to be able to help.
> See below for comments ..
>
> > --- a/net/core/gen_estimator.c 2007-06-25 02:21:48.000000000 +0300
> > +++ b/net/core/gen_estimator.c 2007-07-09 14:27:12.053336875 +0300
> > @@ -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 +89,27 @@
> > u32 last_packets;
> > u32 avpps;
> > u32 avbps;
> > + struct rcu_head e_rcu;
>
>
> You could also use synchronize_rcu(), estimator destruction is
> not particulary performance critical.
I've tried synchronize_rcu(), but it went kaboom with the below, thus
call_rcu() must stay:
---cut---
BUG: sleeping function called from invalid context at kernel/sched.c:3928
in_atomic():1, irqs_disabled():0
3 locks held by tc/2933:
#0: (rtnl_mutex){--..}, at: [<c0296e0a>] rtnetlink_rcv+0x18/0x42
#1: (&dev->queue_lock){-+..}, at: [<c029c337>] qdisc_lock_tree+0xe/0x1c
#2: (&dev->ingress_lock){-...}, at: [<c029dfb8>] tc_get_qdisc+0x192/0x1e9
[<c02eec9e>] wait_for_completion+0x1a/0xb7
[<c01e3cd4>] __spin_lock_init+0x29/0x4b
[<c012e410>] synchronize_rcu+0x2a/0x2f
[<c012e0bc>] wakeme_after_rcu+0x0/0x8
[<c028da00>] gen_kill_estimator+0x70/0x9b
[<f8b7c5a6>] htb_destroy_class+0x27/0x12f [sch_htb]
[<f8b7d037>] htb_destroy+0x34/0x70 [sch_htb]
[<c029c554>] qdisc_destroy+0x44/0x69
.
.
.
---cut---
> > static struct gen_estimator_head elist[EST_MAX_INTERVAL+1];
> >
> > /* Estimator array lock */
> > -static DEFINE_RWLOCK(est_lock);
> > +static DEFINE_SPINLOCK(est_lock);
>
>
> The lock isn't needed anymore since we can rely on the rtnl
> for creation/destruction.
The 'est_lock' now completely removed.
> > /**
> > @@ -152,6 +153,7 @@
> > {
> > struct gen_estimator *est;
> > struct gnet_estimator *parm = RTA_DATA(opt);
> > + int idx;
> >
> > if (RTA_PAYLOAD(opt) < sizeof(*parm))
> > return -EINVAL;
> > @@ -163,7 +165,8 @@
> > if (est == NULL)
> > return -ENOBUFS;
> >
> > - est->interval = parm->interval + 2;
> > + INIT_LIST_HEAD(&est->list);
>
>
> Initializing the members' list_head isn't necessary.
>
Removed.
All the changes above now included in the attached patch. I've clean
compiled it with 2.6.22 and now testing this version.
R.
--- a/net/core/gen_estimator.c 2007-06-25 02:21:48.000000000 +0300
+++ b/net/core/gen_estimator.c 2007-07-09 19:08:06.801544963 +0300
@@ -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 @@
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;
@@ -127,9 +125,9 @@
e->rate_est->pps = (e->avpps+0x1FF)>>10;
spin_unlock(e->stats_lock);
}
-
- mod_timer(&elist[idx].timer, jiffies + ((HZ<<idx)/4));
- read_unlock(&est_lock);
+ if (!list_empty(&elist[idx].list))
+ mod_timer(&elist[idx].timer, jiffies + ((HZ<<idx)/4));
+ rcu_read_unlock();
}
/**
@@ -152,6 +150,7 @@
{
struct gen_estimator *est;
struct gnet_estimator *parm = RTA_DATA(opt);
+ int idx;
if (RTA_PAYLOAD(opt) < sizeof(*parm))
return -EINVAL;
@@ -163,7 +162,7 @@
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;
@@ -173,20 +172,24 @@
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[est->interval].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
@@ -199,26 +202,21 @@
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);
}
}
