From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH] pkt_sched: gen_kill_estimator() rcu fixes Date: Wed, 09 Jun 2010 14:09:23 +0200 Message-ID: <1276085363.2442.125.camel@edumazet-laptop> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Changli Gao , David Miller , netdev , Stephen Hemminger , Patrick McHardy To: Jarek Poplawski Return-path: Received: from mail-wy0-f174.google.com ([74.125.82.174]:48640 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753764Ab0FIMJb (ORCPT ); Wed, 9 Jun 2010 08:09:31 -0400 Received: by wyb40 with SMTP id 40so57441wyb.19 for ; Wed, 09 Jun 2010 05:09:29 -0700 (PDT) In-Reply-To: <20100609104100.GB7308@ff.dom.local> Sender: netdev-owner@vger.kernel.org List-ID: Le mercredi 09 juin 2010 =C3=A0 10:41 +0000, Jarek Poplawski a =C3=A9cr= it : > 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 Thanks for reviewing, you are right about typo and adding some comments= =2E 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=20 (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 --- 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 =20 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; }; =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 *h= ead) * * Removes the rate estimator specified by &bstats and &rate_est. * + * Note : Caller should respect an RCU grace period before freeing sta= ts_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 *na= me) } 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_fre= e_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 *hinfo= ) { unsigned int h =3D tcf_hash(p->tcfc_index, hinfo->hmask); @@ -38,7 +43,11 @@ void tcf_hash_destroy(struct tcf_common *p, struct t= cf_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_fre= e_rcu) */ } =20 module_init(police_init_module);