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Message-ID: <1276085363.2442.125.camel@edumazet-laptop>
Date: Wed, 09 Jun 2010 14:09:23 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: Jarek Poplawski <jarkao2@...il.com>
Cc: Changli Gao <xiaosuo@...il.com>,
David Miller <davem@...emloft.net>,
netdev <netdev@...r.kernel.org>,
Stephen Hemminger <shemminger@...tta.com>,
Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH] pkt_sched: gen_kill_estimator() rcu fixes
Le mercredi 09 juin 2010 à 10:41 +0000, Jarek Poplawski a écrit :
> Spelling suggestion: xt_rateest_free_rcu?
>
> Since it's only 3 places I'd consider adding little comments,
> who needs this call_rcu (like in qdisc_destroy).
>
> Anyway this patch looks OK to me.
>
Thanks for reviewing, you are right about typo and adding some comments.
What about following ?
[PATCH v2] pkt_sched: gen_kill_estimator() rcu fixes
gen_kill_estimator() API is incomplete or not well documented, since
caller should make sure an RCU grace period is respected before
freeing stats_lock.
This was partially addressed in commit 5d944c640b4
(gen_estimator: deadlock fix), but same problem exist for all
gen_kill_estimator() users, if lock they use is not already RCU
protected.
A code review shows xt_RATEEST.c, act_api.c, act_police.c have this
problem. Other are ok because they use qdisc lock, already RCU
protected.
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
include/net/act_api.h | 2 ++
include/net/netfilter/xt_rateest.h | 1 +
net/core/gen_estimator.c | 1 +
net/netfilter/xt_RATEEST.c | 12 +++++++++++-
net/sched/act_api.c | 11 ++++++++++-
net/sched/act_police.c | 12 +++++++++++-
6 files changed, 36 insertions(+), 3 deletions(-)
diff --git a/include/net/act_api.h b/include/net/act_api.h
index c05fd71..bab385f 100644
--- a/include/net/act_api.h
+++ b/include/net/act_api.h
@@ -20,6 +20,7 @@ struct tcf_common {
struct gnet_stats_queue tcfc_qstats;
struct gnet_stats_rate_est tcfc_rate_est;
spinlock_t tcfc_lock;
+ struct rcu_head tcfc_rcu;
};
#define tcf_next common.tcfc_next
#define tcf_index common.tcfc_index
@@ -32,6 +33,7 @@ struct tcf_common {
#define tcf_qstats common.tcfc_qstats
#define tcf_rate_est common.tcfc_rate_est
#define tcf_lock common.tcfc_lock
+#define tcf_rcu common.tcfc_rcu
struct tcf_police {
struct tcf_common common;
diff --git a/include/net/netfilter/xt_rateest.h b/include/net/netfilter/xt_rateest.h
index ddbf37e..5e14277 100644
--- a/include/net/netfilter/xt_rateest.h
+++ b/include/net/netfilter/xt_rateest.h
@@ -9,6 +9,7 @@ struct xt_rateest {
struct gnet_estimator params;
struct gnet_stats_rate_est rstats;
struct gnet_stats_basic_packed bstats;
+ struct rcu_head rcu;
};
extern struct xt_rateest *xt_rateest_lookup(const char *name);
diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c
index 785e527..9fbe7f7 100644
--- a/net/core/gen_estimator.c
+++ b/net/core/gen_estimator.c
@@ -263,6 +263,7 @@ static void __gen_kill_estimator(struct rcu_head *head)
*
* Removes the rate estimator specified by &bstats and &rate_est.
*
+ * Note : Caller should respect an RCU grace period before freeing stats_lock
*/
void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
struct gnet_stats_rate_est *rate_est)
diff --git a/net/netfilter/xt_RATEEST.c b/net/netfilter/xt_RATEEST.c
index 69c01e1..de079ab 100644
--- a/net/netfilter/xt_RATEEST.c
+++ b/net/netfilter/xt_RATEEST.c
@@ -60,13 +60,22 @@ struct xt_rateest *xt_rateest_lookup(const char *name)
}
EXPORT_SYMBOL_GPL(xt_rateest_lookup);
+static void xt_rateest_free_rcu(struct rcu_head *head)
+{
+ kfree(container_of(head, struct xt_rateest, rcu));
+}
+
void xt_rateest_put(struct xt_rateest *est)
{
mutex_lock(&xt_rateest_mutex);
if (--est->refcnt == 0) {
hlist_del(&est->list);
gen_kill_estimator(&est->bstats, &est->rstats);
- kfree(est);
+ /*
+ * gen_estimator est_timer() might access est->lock or bstats,
+ * wait a RCU grace period before freeing 'est'
+ */
+ call_rcu(&est->rcu, xt_rateest_free_rcu);
}
mutex_unlock(&xt_rateest_mutex);
}
@@ -179,6 +188,7 @@ static int __init xt_rateest_tg_init(void)
static void __exit xt_rateest_tg_fini(void)
{
xt_unregister_target(&xt_rateest_tg_reg);
+ rcu_barrier(); /* Wait for completion of call_rcu()'s (xt_rateest_free_rcu) */
}
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 972378f..23b25f8 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -26,6 +26,11 @@
#include <net/act_api.h>
#include <net/netlink.h>
+static void tcf_common_free_rcu(struct rcu_head *head)
+{
+ kfree(container_of(head, struct tcf_common, tcfc_rcu));
+}
+
void tcf_hash_destroy(struct tcf_common *p, struct tcf_hashinfo *hinfo)
{
unsigned int h = tcf_hash(p->tcfc_index, hinfo->hmask);
@@ -38,7 +43,11 @@ void tcf_hash_destroy(struct tcf_common *p, struct tcf_hashinfo *hinfo)
write_unlock_bh(hinfo->lock);
gen_kill_estimator(&p->tcfc_bstats,
&p->tcfc_rate_est);
- kfree(p);
+ /*
+ * gen_estimator est_timer() might access p->tcfc_lock
+ * or bstats, wait a RCU grace period before freeing p
+ */
+ call_rcu(&p->tcfc_rcu, tcf_common_free_rcu);
return;
}
}
diff --git a/net/sched/act_police.c b/net/sched/act_police.c
index 654f73d..537a487 100644
--- a/net/sched/act_police.c
+++ b/net/sched/act_police.c
@@ -97,6 +97,11 @@ nla_put_failure:
goto done;
}
+static void tcf_police_free_rcu(struct rcu_head *head)
+{
+ kfree(container_of(head, struct tcf_police, tcf_rcu));
+}
+
static void tcf_police_destroy(struct tcf_police *p)
{
unsigned int h = tcf_hash(p->tcf_index, POL_TAB_MASK);
@@ -113,7 +118,11 @@ static void tcf_police_destroy(struct tcf_police *p)
qdisc_put_rtab(p->tcfp_R_tab);
if (p->tcfp_P_tab)
qdisc_put_rtab(p->tcfp_P_tab);
- kfree(p);
+ /*
+ * gen_estimator est_timer() might access p->tcf_lock
+ * or bstats, wait a RCU grace period before freeing p
+ */
+ call_rcu(&p->tcf_rcu, tcf_police_free_rcu);
return;
}
}
@@ -397,6 +406,7 @@ static void __exit
police_cleanup_module(void)
{
tcf_unregister_action(&act_police_ops);
+ rcu_barrier(); /* Wait for completion of call_rcu()'s (tcf_police_free_rcu) */
}
module_init(police_init_module);
--
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