From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: Re: [PATCH] pkt_sched: gen_kill_estimator() rcu fixes Date: Wed, 9 Jun 2010 12:50:35 +0000 Message-ID: <20100609125035.GD7308@ff.dom.local> References: <1275921171.2545.102.camel@edumazet-laptop> <1275924638.2545.121.camel@edumazet-laptop> <1275926151.2545.126.camel@edumazet-laptop> <1275929761.2545.159.camel@edumazet-laptop> <1276076415.2442.92.camel@edumazet-laptop> <1276077416.2442.97.camel@edumazet-laptop> <20100609104100.GB7308@ff.dom.local> <1276085363.2442.125.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Changli Gao , David Miller , netdev , Stephen Hemminger , Patrick McHardy To: Eric Dumazet Return-path: Received: from mail-fx0-f46.google.com ([209.85.161.46]:33706 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757391Ab0FIMuj (ORCPT ); Wed, 9 Jun 2010 08:50:39 -0400 Received: by fxm8 with SMTP id 8so3550377fxm.19 for ; Wed, 09 Jun 2010 05:50:38 -0700 (PDT) Content-Disposition: inline In-Reply-To: <1276085363.2442.125.camel@edumazet-laptop> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Jun 09, 2010 at 02:09:23PM +0200, Eric Dumazet wrote: > Le mercredi 09 juin 2010 ?? 10:41 +0000, Jarek Poplawski a =E9crit : >=20 > > Spelling suggestion: xt_rateest_free_rcu? > >=20 > > Since it's only 3 places I'd consider adding little comments, > > who needs this call_rcu (like in qdisc_destroy). > >=20 > > Anyway this patch looks OK to me. > >=20 >=20 > Thanks for reviewing, you are right about typo and adding some commen= ts. >=20 > What about following ? Very nice! (But let's remember these comments aren't very precise wrt. bstats at the moment ;-) Thanks, Jarek P. >=20 > [PATCH v2] pkt_sched: gen_kill_estimator() rcu fixes >=20 > 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. >=20 > This was partially addressed in commit 5d944c640b4=20 > (gen_estimator: deadlock fix), but same problem exist for all > gen_kill_estimator() users, if lock they use is not already RCU > protected. >=20 > 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. >=20 > Signed-off-by: Eric Dumazet > --- > 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(-) >=20 > 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 > =20 > struct tcf_police { > struct tcf_common common; > diff --git a/include/net/netfilter/xt_rateest.h b/include/net/netfilt= er/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; > }; > =20 > 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 s= tats_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); > =20 > +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 =3D=3D 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_f= ree_rcu) */ > } > =20 > =20 > 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 > #include > =20 > +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 *hin= fo) > { > unsigned int h =3D 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; > } > =20 > +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 =3D 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_f= ree_rcu) */ > } > =20 > module_init(police_init_module); >=20 >=20