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=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 27D27C76196 for ; Tue, 16 Jul 2019 18:47:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 072562173C for ; Tue, 16 Jul 2019 18:47:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="dmMkHQo9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388539AbfGPSrC (ORCPT ); Tue, 16 Jul 2019 14:47:02 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:42516 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388107AbfGPSqw (ORCPT ); Tue, 16 Jul 2019 14:46:52 -0400 Received: by mail-pg1-f196.google.com with SMTP id t132so9862523pgb.9 for ; Tue, 16 Jul 2019 11:46:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=PdG0Hdy4kUF1vNp70B1fm6NDyRSJQdtEoyDsUyLFi94=; b=dmMkHQo9IniciAwKAMxr0u85jWCSvyb5BF57+I4CD3SZq9AT5BU5o2HZO4fS84Qgrb x4dLWUS32mTEUlCn5agl3nUCtKJ2BiYYgquJpGEVAqF+/lZwg41ad0k1NH/k0y7e+3YR RXTcC5Vge/zfplv3AXO+eEIhtj5K1O5b0vSbM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=PdG0Hdy4kUF1vNp70B1fm6NDyRSJQdtEoyDsUyLFi94=; b=MTEWi+Muc69L/nwW9DSE+N1W0F9wTSgEt0k/45j6idzw8AqUjmXHNfyv0iwMTxWhnw Mwv4NyQBr5neBoYhQwBTa8JdLil7OJJhZHdGCvN4HEdm5E6pJqnxWkmY633bxQMjxgNM 5XRFjngtTZr2G6JZqqQBJ7LA/L4rgtvdp2ijkf1n+Iza/m4Z89FVSowRbOlWpHF7n6oA ncgFlzT/SsTzjyv1uxe3/6xgsAy1Jf1ISSdB94KKVvGX6R/MNQl1a7zF74gEdfTdnITy ohEBQrcxGRyL63VNd61RMxULB2NXq5bp2b+XEaZcay0OPvUUz7VKlUgn769TdA3XAM88 2kng== X-Gm-Message-State: APjAAAWvtR0NJj0Bw/H9PF9a+eqdUUhnbKmxy6AT37LW8g/wp1WPuNMI g22OMXj8VBiaPP7SOs+SUD4= X-Google-Smtp-Source: APXvYqwkKBelwwXf63Pw3fAr18WLABRKFaDv/myKEWHJ+6vqtjhnwmRdixzh6Ckd3GBE6woFO+E/Pw== X-Received: by 2002:a17:90a:b387:: with SMTP id e7mr39873248pjr.113.1563302811662; Tue, 16 Jul 2019 11:46:51 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id f19sm28628190pfk.180.2019.07.16.11.46.50 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 16 Jul 2019 11:46:50 -0700 (PDT) Date: Tue, 16 Jul 2019 14:46:49 -0400 From: Joel Fernandes To: "Paul E. McKenney" 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) Message-ID: <20190716184649.GA130463@google.com> References: <20190715143705.117908-1-joel@joelfernandes.org> <20190715143705.117908-3-joel@joelfernandes.org> <20190716183833.GD14271@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190716183833.GD14271@linux.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 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. But I don't mind dropping it and it may just accelerate the fixing up of all callers. > > +#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!