From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 067D6C7618F for ; Tue, 16 Jul 2019 18:53:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA5FB20665 for ; Tue, 16 Jul 2019 18:53:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728495AbfGPSxR (ORCPT ); Tue, 16 Jul 2019 14:53:17 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:51966 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728575AbfGPSxQ (ORCPT ); Tue, 16 Jul 2019 14:53:16 -0400 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x6GIqQFv135491 for ; Tue, 16 Jul 2019 14:53:16 -0400 Received: from e16.ny.us.ibm.com (e16.ny.us.ibm.com [129.33.205.206]) by mx0b-001b2d01.pphosted.com with ESMTP id 2tsha4f9xy-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 16 Jul 2019 14:53:15 -0400 Received: from localhost by e16.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 16 Jul 2019 19:53:05 +0100 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp22036.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x6GIr4HN37159330 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 16 Jul 2019 18:53:04 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4A27FB2067; Tue, 16 Jul 2019 18:53:04 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E778DB2064; Tue, 16 Jul 2019 18:53:03 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.80.225.134]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Tue, 16 Jul 2019 18:53:03 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 011B016C8E9B; Tue, 16 Jul 2019 11:53:03 -0700 (PDT) Date: Tue, 16 Jul 2019 11:53:03 -0700 From: "Paul E. McKenney" To: Joel Fernandes Cc: linux-kernel@vger.kernel.org, Alexey Kuznetsov , Bjorn Helgaas , Borislav Petkov , c0d1n61at3@gmail.com, "David S. Miller" , edumazet@google.com, Greg Kroah-Hartman , Hideaki YOSHIFUJI , "H. Peter Anvin" , Ingo Molnar , Jonathan Corbet , Josh Triplett , keescook@chromium.org, kernel-hardening@lists.openwall.com, kernel-team@android.com, Lai Jiangshan , Len Brown , linux-acpi@vger.kernel.org, linux-doc@vger.kernel.org, linux-pci@vger.kernel.org, linux-pm@vger.kernel.org, Mathieu Desnoyers , neilb@suse.com, netdev@vger.kernel.org, Oleg Nesterov , Pavel Machek , peterz@infradead.org, "Rafael J. Wysocki" , Rasmus Villemoes , rcu@vger.kernel.org, Steven Rostedt , Tejun Heo , Thomas Gleixner , will@kernel.org, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" Subject: Re: [PATCH 2/9] rcu: Add support for consolidated-RCU reader checking (v3) Reply-To: paulmck@linux.ibm.com References: <20190715143705.117908-1-joel@joelfernandes.org> <20190715143705.117908-3-joel@joelfernandes.org> <20190716183833.GD14271@linux.ibm.com> <20190716184649.GA130463@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190716184649.GA130463@google.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19071618-0072-0000-0000-00000449B137 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011440; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000286; SDB=6.01233111; UDB=6.00649721; IPR=6.01014423; MB=3.00027748; MTD=3.00000008; XFM=3.00000015; UTC=2019-07-16 18:53:14 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19071618-0073-0000-0000-00004CB9FCC3 Message-Id: <20190716185303.GM14271@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-07-16_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1907160231 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Tue, Jul 16, 2019 at 02:46:49PM -0400, Joel Fernandes wrote: > On Tue, Jul 16, 2019 at 11:38:33AM -0700, Paul E. McKenney wrote: > > On Mon, Jul 15, 2019 at 10:36:58AM -0400, Joel Fernandes (Google) wrote: > > > This patch adds support for checking RCU reader sections in list > > > traversal macros. Optionally, if the list macro is called under SRCU or > > > other lock/mutex protection, then appropriate lockdep expressions can be > > > passed to make the checks pass. > > > > > > Existing list_for_each_entry_rcu() invocations don't need to pass the > > > optional fourth argument (cond) unless they are under some non-RCU > > > protection and needs to make lockdep check pass. > > > > > > Signed-off-by: Joel Fernandes (Google) > > > > Now that I am on the correct version, again please fold in the checks > > for the extra argument. The ability to have an optional argument looks > > quite helpful, especially when compared to growing the RCU API! > > I did fold this and replied with a pull request URL based on /dev branch. But > we can hold off on the pull requests until we decide on the below comments: > > > A few more things below. > > > --- > > > include/linux/rculist.h | 28 ++++++++++++++++++++----- > > > include/linux/rcupdate.h | 7 +++++++ > > > kernel/rcu/Kconfig.debug | 11 ++++++++++ > > > kernel/rcu/update.c | 44 ++++++++++++++++++++++++---------------- > > > 4 files changed, 67 insertions(+), 23 deletions(-) > > > > > > diff --git a/include/linux/rculist.h b/include/linux/rculist.h > > > index e91ec9ddcd30..1048160625bb 100644 > > > --- a/include/linux/rculist.h > > > +++ b/include/linux/rculist.h > > > @@ -40,6 +40,20 @@ static inline void INIT_LIST_HEAD_RCU(struct list_head *list) > > > */ > > > #define list_next_rcu(list) (*((struct list_head __rcu **)(&(list)->next))) > > > > > > +/* > > > + * Check during list traversal that we are within an RCU reader > > > + */ > > > + > > > +#ifdef CONFIG_PROVE_RCU_LIST > > > > This new Kconfig option is OK temporarily, but unless there is reason to > > fear malfunction that a few weeks of rcutorture, 0day, and -next won't > > find, it would be better to just use CONFIG_PROVE_RCU. The overall goal > > is to reduce the number of RCU knobs rather than grow them, must though > > history might lead one to believe otherwise. :-/ > > If you want, we can try to drop this option and just use PROVE_RCU however I > must say there may be several warnings that need to be fixed in a short > period of time (even a few weeks may be too short) considering the 1000+ > uses of RCU lists. Do many people other than me build with CONFIG_PROVE_RCU? If so, then that would be a good reason for a temporary CONFIG_PROVE_RCU_LIST, as in going away in a release or two once the warnings get fixed. > But I don't mind dropping it and it may just accelerate the fixing up of all > callers. I will let you decide based on the above question. But if you have CONFIG_PROVE_RCU_LIST, as noted below, it needs to depend on RCU_EXPERT. Thanx, Paul > > > +#define __list_check_rcu(dummy, cond, ...) \ > > > + ({ \ > > > + RCU_LOCKDEP_WARN(!cond && !rcu_read_lock_any_held(), \ > > > + "RCU-list traversed in non-reader section!"); \ > > > + }) > > > +#else > > > +#define __list_check_rcu(dummy, cond, ...) ({}) > > > +#endif > > > + > > > /* > > > * Insert a new entry between two known consecutive entries. > > > * > > > @@ -343,14 +357,16 @@ static inline void list_splice_tail_init_rcu(struct list_head *list, > > > * @pos: the type * to use as a loop cursor. > > > * @head: the head for your list. > > > * @member: the name of the list_head within the struct. > > > + * @cond: optional lockdep expression if called from non-RCU protection. > > > * > > > * This list-traversal primitive may safely run concurrently with > > > * the _rcu list-mutation primitives such as list_add_rcu() > > > * as long as the traversal is guarded by rcu_read_lock(). > > > */ > > > -#define list_for_each_entry_rcu(pos, head, member) \ > > > - for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \ > > > - &pos->member != (head); \ > > > +#define list_for_each_entry_rcu(pos, head, member, cond...) \ > > > + for (__list_check_rcu(dummy, ## cond, 0), \ > > > + pos = list_entry_rcu((head)->next, typeof(*pos), member); \ > > > + &pos->member != (head); \ > > > pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) > > > > > > /** > > > @@ -616,13 +632,15 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n, > > > * @pos: the type * to use as a loop cursor. > > > * @head: the head for your list. > > > * @member: the name of the hlist_node within the struct. > > > + * @cond: optional lockdep expression if called from non-RCU protection. > > > * > > > * This list-traversal primitive may safely run concurrently with > > > * the _rcu list-mutation primitives such as hlist_add_head_rcu() > > > * as long as the traversal is guarded by rcu_read_lock(). > > > */ > > > -#define hlist_for_each_entry_rcu(pos, head, member) \ > > > - for (pos = hlist_entry_safe (rcu_dereference_raw(hlist_first_rcu(head)),\ > > > +#define hlist_for_each_entry_rcu(pos, head, member, cond...) \ > > > + for (__list_check_rcu(dummy, ## cond, 0), \ > > > + pos = hlist_entry_safe (rcu_dereference_raw(hlist_first_rcu(head)),\ > > > typeof(*(pos)), member); \ > > > pos; \ > > > pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\ > > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > > > index 8f7167478c1d..f3c29efdf19a 100644 > > > --- a/include/linux/rcupdate.h > > > +++ b/include/linux/rcupdate.h > > > @@ -221,6 +221,7 @@ int debug_lockdep_rcu_enabled(void); > > > int rcu_read_lock_held(void); > > > int rcu_read_lock_bh_held(void); > > > int rcu_read_lock_sched_held(void); > > > +int rcu_read_lock_any_held(void); > > > > > > #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ > > > > > > @@ -241,6 +242,12 @@ static inline int rcu_read_lock_sched_held(void) > > > { > > > return !preemptible(); > > > } > > > + > > > +static inline int rcu_read_lock_any_held(void) > > > +{ > > > + return !preemptible(); > > > +} > > > + > > > #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ > > > > > > #ifdef CONFIG_PROVE_RCU > > > diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug > > > index 5ec3ea4028e2..7fbd21dbfcd0 100644 > > > --- a/kernel/rcu/Kconfig.debug > > > +++ b/kernel/rcu/Kconfig.debug > > > @@ -8,6 +8,17 @@ menu "RCU Debugging" > > > config PROVE_RCU > > > def_bool PROVE_LOCKING > > > > > > +config PROVE_RCU_LIST > > > + bool "RCU list lockdep debugging" > > > + depends on PROVE_RCU > > > > This must also depend on RCU_EXPERT. > > Sure. > > > > + default n > > > + help > > > + Enable RCU lockdep checking for list usages. By default it is > > > + turned off since there are several list RCU users that still > > > + need to be converted to pass a lockdep expression. To prevent > > > + false-positive splats, we keep it default disabled but once all > > > + users are converted, we can remove this config option. > > > + > > > config TORTURE_TEST > > > tristate > > > default n > > > diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c > > > index 9dd5aeef6e70..b7a4e3b5fa98 100644 > > > --- a/kernel/rcu/update.c > > > +++ b/kernel/rcu/update.c > > > @@ -91,14 +91,18 @@ module_param(rcu_normal_after_boot, int, 0); > > > * Similarly, we avoid claiming an SRCU read lock held if the current > > > * CPU is offline. > > > */ > > > +#define rcu_read_lock_held_common() \ > > > + if (!debug_lockdep_rcu_enabled()) \ > > > + return 1; \ > > > + if (!rcu_is_watching()) \ > > > + return 0; \ > > > + if (!rcu_lockdep_current_cpu_online()) \ > > > + return 0; > > > > Nice abstraction of common code! > > Thanks! >