From patchwork Mon Jul 15 14:36:57 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 1132061 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=joelfernandes.org Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="QjihkdzO"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45nRCM3hWtz9sVp for ; Tue, 16 Jul 2019 00:45:19 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390924AbfGOOpS (ORCPT ); Mon, 15 Jul 2019 10:45:18 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:46638 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404384AbfGOOhS (ORCPT ); Mon, 15 Jul 2019 10:37:18 -0400 Received: by mail-pg1-f196.google.com with SMTP id i8so7793397pgm.13 for ; Mon, 15 Jul 2019 07:37:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=peLCyvMnb6GAqXrVywa8AT70STEJ77uX6TkkVXJzQ/M=; b=QjihkdzO56EyWdL1UBrowr4J0diPIpjeawlNo5eUXRlutEI+PMdDLg/2ovhGCm9dB1 am3dJfpAJ98Tx9IokTbTDJI/QLnhNHnLoi+VI/95oP5fp/RwwQCZGPG9aCEKUlUpO/1N atHPVJ+wXVzYcfg26NNOs6IX7iznL6Gp2AAwA= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=peLCyvMnb6GAqXrVywa8AT70STEJ77uX6TkkVXJzQ/M=; b=GYmNlePgt5jqdyOW/USI2u9ZRWYA053ObBB8InUD21c5WPXG3FKuSPxnhyDFE5Ku2Y Bmucz7jEBcGEWy+kjr+o+NJlP/w9gm+iunIDMhN7fsbyOlpJl56CKSBRWDBMUcldvlGU d4Xhv0m8keOFmPDKM+VzK82Flm7bHOM4LgxHOX8quW9QEPqoLRjVatew+79Czl2E12JU +91O3+FhbciSF8yhYbt1cBy1dT5KxfbflFraAPvDbe5wq78nn55ysqoTQMApFm0pktg5 2iavP8cpeXGLOMmoD//FSC8BkZZMdfWQNOEHO6ru6Y/7VBoQIX/RiDisAem0YRUTzeL9 BYcQ== X-Gm-Message-State: APjAAAVX8oOEDLeMGMjT5kR4VxWyYfJvAbz7rAKgBb9GfCyXzjSJQ7+e wSQOEpc9hH2YFVZ5gmsppCg= X-Google-Smtp-Source: APXvYqzmK9tD8rYXtIru39NtpVyI6dVamC0JOl/Vm3L4KkimM24dL0CBqeO9C1zAEuPYG8wK9FgMFA== X-Received: by 2002:a65:6281:: with SMTP id f1mr25763664pgv.400.1563201437978; Mon, 15 Jul 2019 07:37:17 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id s66sm18381852pfs.8.2019.07.15.07.37.14 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 15 Jul 2019 07:37:17 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , 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 , "Paul E. McKenney" , Pavel Machek , peterz@infradead.org, "Rafael J. Wysocki" , Rasmus Villemoes , rcu@vger.kernel.org, Steven Rostedt , Tejun Heo , Thomas Gleixner , will@kernel.org, x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Subject: [PATCH 1/9] rcu/update: Remove useless check for debug_locks (v1) Date: Mon, 15 Jul 2019 10:36:57 -0400 Message-Id: <20190715143705.117908-2-joel@joelfernandes.org> X-Mailer: git-send-email 2.22.0.510.g264f2c817a-goog In-Reply-To: <20190715143705.117908-1-joel@joelfernandes.org> References: <20190715143705.117908-1-joel@joelfernandes.org> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org In rcu_read_lock_sched_held(), debug_locks can never be true at the point we check it because we already check debug_locks in debug_lockdep_rcu_enabled() in the beginning. Remove the check. Signed-off-by: Joel Fernandes (Google) --- kernel/rcu/update.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index 61df2bf08563..9dd5aeef6e70 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -93,17 +93,13 @@ module_param(rcu_normal_after_boot, int, 0); */ int rcu_read_lock_sched_held(void) { - int lockdep_opinion = 0; - if (!debug_lockdep_rcu_enabled()) return 1; if (!rcu_is_watching()) return 0; if (!rcu_lockdep_current_cpu_online()) return 0; - if (debug_locks) - lockdep_opinion = lock_is_held(&rcu_sched_lock_map); - return lockdep_opinion || !preemptible(); + return lock_is_held(&rcu_sched_lock_map) || !preemptible(); } EXPORT_SYMBOL(rcu_read_lock_sched_held); #endif From patchwork Mon Jul 15 14:36:58 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 1132064 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=joelfernandes.org Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="IozIr9z+"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45nRFH0BcQzB3vc for ; Tue, 16 Jul 2019 00:46:59 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405136AbfGOOq5 (ORCPT ); Mon, 15 Jul 2019 10:46:57 -0400 Received: from mail-pl1-f196.google.com ([209.85.214.196]:45708 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404482AbfGOOhX (ORCPT ); Mon, 15 Jul 2019 10:37:23 -0400 Received: by mail-pl1-f196.google.com with SMTP id y8so8382539plr.12 for ; Mon, 15 Jul 2019 07:37:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=CJEwPPrtJyDTV3piEkDE+ONyRMH9m2RDRbmoV5ZEGS8=; b=IozIr9z+GIb5mPdKiPaf5UHiYIz+Oat0gqj58xKeNgOqIcav4VXtm41dS18QhgHWuP 08bOfzHsvFlkA1+slmz0mYgCQced6RM3EOenJJaGW8k4oiXykx/eoqvUaynExjS780ga gIRPex9R8tFcEqFj6fn/uCxhibShb2XLfLQao= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=CJEwPPrtJyDTV3piEkDE+ONyRMH9m2RDRbmoV5ZEGS8=; b=SGABz6YIHhXob0WDoUUSWXamYc59GLr0ZOKB9aQGDCZ9ewq01/8oqINZAZvUdBOyeg RziqdDAzbChZ48I3MNfo+i0m0b6v1URSsw5IdZPo5oUZVOiM8qcQjNeLOkSY4iImYeQb J/7GNxhuQqalRolTNT3wZko1BDxbJKattLJS6sRDfN+YzoONkLcBvPR3+093zr6wCR6J 1PXoFH1tX+aCEZv+Adc1KhiSvj7hO+xe4A0y7yQ1Z1NPPvSpKzCGDstihmbFW/2+KFz8 qF+7Zx8oS9V4WeK3v6iJ5I9YlfgEj40DWBZvwH4Zfg748hmQOn3EatGlURjuP1B6weZN M2Pg== X-Gm-Message-State: APjAAAVtLVo5iPjaeqrq5ogiG2LvMsnecgizTPAyDkh9tktP+rjEyg1Y GjKOrcGRq2PEQ0p3kcwqP8M= X-Google-Smtp-Source: APXvYqzrTtDshfHRTIApwfR2uw8rmwlBdmV5rfV/lQ/WFFtfVs/RxHxaLHWVf+yG1vS25zf50JO+qA== X-Received: by 2002:a17:902:290b:: with SMTP id g11mr28300017plb.26.1563201442188; Mon, 15 Jul 2019 07:37:22 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id s66sm18381852pfs.8.2019.07.15.07.37.18 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 15 Jul 2019 07:37:21 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , 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 , "Paul E. McKenney" , Pavel Machek , peterz@infradead.org, "Rafael J. Wysocki" , Rasmus Villemoes , rcu@vger.kernel.org, Steven Rostedt , Tejun Heo , Thomas Gleixner , will@kernel.org, x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Subject: [PATCH 2/9] rcu: Add support for consolidated-RCU reader checking (v3) Date: Mon, 15 Jul 2019 10:36:58 -0400 Message-Id: <20190715143705.117908-3-joel@joelfernandes.org> X-Mailer: git-send-email 2.22.0.510.g264f2c817a-goog In-Reply-To: <20190715143705.117908-1-joel@joelfernandes.org> References: <20190715143705.117908-1-joel@joelfernandes.org> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org 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) --- 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 +#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 + 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; + int rcu_read_lock_sched_held(void) { - if (!debug_lockdep_rcu_enabled()) - return 1; - if (!rcu_is_watching()) - return 0; - if (!rcu_lockdep_current_cpu_online()) - return 0; + rcu_read_lock_held_common(); + return lock_is_held(&rcu_sched_lock_map) || !preemptible(); } EXPORT_SYMBOL(rcu_read_lock_sched_held); @@ -257,12 +261,8 @@ NOKPROBE_SYMBOL(debug_lockdep_rcu_enabled); */ int rcu_read_lock_held(void) { - if (!debug_lockdep_rcu_enabled()) - return 1; - if (!rcu_is_watching()) - return 0; - if (!rcu_lockdep_current_cpu_online()) - return 0; + rcu_read_lock_held_common(); + return lock_is_held(&rcu_lock_map); } EXPORT_SYMBOL_GPL(rcu_read_lock_held); @@ -284,16 +284,24 @@ EXPORT_SYMBOL_GPL(rcu_read_lock_held); */ int rcu_read_lock_bh_held(void) { - if (!debug_lockdep_rcu_enabled()) - return 1; - if (!rcu_is_watching()) - return 0; - if (!rcu_lockdep_current_cpu_online()) - return 0; + rcu_read_lock_held_common(); + return in_softirq() || irqs_disabled(); } EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); +int rcu_read_lock_any_held(void) +{ + rcu_read_lock_held_common(); + + if (lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_sched_lock_map)) + return 1; + return !preemptible(); +} +EXPORT_SYMBOL_GPL(rcu_read_lock_any_held); + #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ /** From patchwork Mon Jul 15 14:36:59 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 1132046 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=joelfernandes.org Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="AUubZl4E"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45nR2K0Hjkz9sVC for ; Tue, 16 Jul 2019 00:37:29 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404572AbfGOOh1 (ORCPT ); Mon, 15 Jul 2019 10:37:27 -0400 Received: from mail-pl1-f195.google.com ([209.85.214.195]:39251 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404549AbfGOOh1 (ORCPT ); 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Mon, 15 Jul 2019 07:37:26 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id s66sm18381852pfs.8.2019.07.15.07.37.22 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 15 Jul 2019 07:37:25 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , Oleg Nesterov , 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, "Paul E. McKenney" , Pavel Machek , peterz@infradead.org, "Rafael J. Wysocki" , Rasmus Villemoes , rcu@vger.kernel.org, Steven Rostedt , Tejun Heo , Thomas Gleixner , will@kernel.org, x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Subject: [PATCH 3/9] rcu/sync: Remove custom check for reader-section (v2) Date: Mon, 15 Jul 2019 10:36:59 -0400 Message-Id: <20190715143705.117908-4-joel@joelfernandes.org> X-Mailer: git-send-email 2.22.0.510.g264f2c817a-goog In-Reply-To: <20190715143705.117908-1-joel@joelfernandes.org> References: <20190715143705.117908-1-joel@joelfernandes.org> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org The rcu/sync code was doing its own check whether we are in a reader section. With RCU consolidating flavors and the generic helper added in this series, this is no longer need. We can just use the generic helper and it results in a nice cleanup. Cc: Oleg Nesterov Acked-by: Oleg Nesterov Signed-off-by: Joel Fernandes (Google) --- include/linux/rcu_sync.h | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/include/linux/rcu_sync.h b/include/linux/rcu_sync.h index 9b83865d24f9..0027d4c8087c 100644 --- a/include/linux/rcu_sync.h +++ b/include/linux/rcu_sync.h @@ -31,9 +31,7 @@ struct rcu_sync { */ static inline bool rcu_sync_is_idle(struct rcu_sync *rsp) { - RCU_LOCKDEP_WARN(!rcu_read_lock_held() && - !rcu_read_lock_bh_held() && - !rcu_read_lock_sched_held(), + RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(), "suspicious rcu_sync_is_idle() usage"); return !READ_ONCE(rsp->gp_state); /* GP_IDLE */ } From patchwork Mon Jul 15 14:37:00 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 1132057 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=joelfernandes.org Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="WUpb9JKs"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45nRBS025Hz9sVP for ; Tue, 16 Jul 2019 00:44:31 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404453AbfGOOoa (ORCPT ); Mon, 15 Jul 2019 10:44:30 -0400 Received: from mail-pl1-f196.google.com ([209.85.214.196]:44350 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404702AbfGOOhb (ORCPT ); Mon, 15 Jul 2019 10:37:31 -0400 Received: by mail-pl1-f196.google.com with SMTP id t14so8370659plr.11 for ; Mon, 15 Jul 2019 07:37:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=/gvD5L3W4khYlR/j02/LMhetLZkkRNPQ8EPkwaYb/Yo=; b=WUpb9JKsXzIHcxew1wAVQiWwZ+kaf0Ww3b9i/phqeK6eGSyIkMrGlEABg1JgP/N6a7 XI3TNv1vdpFEoUyT+MAAdsh6eiTQV1SZjNnbyXSh4bYq6H3Gz7K8UhzDuVF/rfbp1RTm xNeitgRKD2kv4LjyEJgK6S9GJGZvS2JWmOhuM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=/gvD5L3W4khYlR/j02/LMhetLZkkRNPQ8EPkwaYb/Yo=; b=bXZXwecxJqujWGCKFfiuVlYMNSlXQRq8eFoQG14F3Pa5eBcgHlFduWSKh/ktDUemwk RUmL1jlUxqKYZKGF5rxVsSMGJubPGVAXJbf6/X2wTdUG6773wTlwl4g76TfpCg1gp8jM jDs0DdnvUKjm/E5xl3mafRLRC8QiSuSDOWS02BUlw28HQcCQDWd6wndEN5ghBF3+/wWG zJ7tXQfw6vsdJZrklg6GSahk/9jdkLGzsVZ319rTbLQk3OyOTKO1lbxwfweOeyewIx+O ars+4UudDk4sxsSVp5JGpFJTMJkR+qViDErBEwq3eN7m6uZPAIcNR/SuHS0SxgPn56eI wrng== X-Gm-Message-State: APjAAAXxwyOkvLwJOOT6e+9/iVj8dsU7AeSnlvUGC5GE94+olGxAprlD W1OVQtFEkY9Aj1QgFtRKnHU= X-Google-Smtp-Source: APXvYqySJr0Y1QIzNUIj9NJwd+Rw22u3LGJjXHmBidac39lx3Xu00PxoUZgolCbZ3bk0iovIh+UXIw== X-Received: by 2002:a17:902:1003:: with SMTP id b3mr29244590pla.172.1563201450419; Mon, 15 Jul 2019 07:37:30 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id s66sm18381852pfs.8.2019.07.15.07.37.26 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 15 Jul 2019 07:37:29 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , 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 , "Paul E. McKenney" , Pavel Machek , peterz@infradead.org, "Rafael J. Wysocki" , Rasmus Villemoes , rcu@vger.kernel.org, Steven Rostedt , Tejun Heo , Thomas Gleixner , will@kernel.org, x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Subject: [PATCH 4/9] ipv4: add lockdep condition to fix for_each_entry (v1) Date: Mon, 15 Jul 2019 10:37:00 -0400 Message-Id: <20190715143705.117908-5-joel@joelfernandes.org> X-Mailer: git-send-email 2.22.0.510.g264f2c817a-goog In-Reply-To: <20190715143705.117908-1-joel@joelfernandes.org> References: <20190715143705.117908-1-joel@joelfernandes.org> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org Using the previous support added, use it for adding lockdep conditions to list usage here. Signed-off-by: Joel Fernandes (Google) Acked-by: David S. Miller --- net/ipv4/fib_frontend.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c index 317339cd7f03..26b0fb24e2c2 100644 --- a/net/ipv4/fib_frontend.c +++ b/net/ipv4/fib_frontend.c @@ -124,7 +124,8 @@ struct fib_table *fib_get_table(struct net *net, u32 id) h = id & (FIB_TABLE_HASHSZ - 1); head = &net->ipv4.fib_table_hash[h]; - hlist_for_each_entry_rcu(tb, head, tb_hlist) { + hlist_for_each_entry_rcu(tb, head, tb_hlist, + lockdep_rtnl_is_held()) { if (tb->tb_id == id) return tb; } From patchwork Mon Jul 15 14:37:01 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 1132047 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=joelfernandes.org Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="GC6kguZw"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45nR2X10fPzB3tZ for ; Tue, 16 Jul 2019 00:37:40 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404733AbfGOOhg (ORCPT ); Mon, 15 Jul 2019 10:37:36 -0400 Received: from mail-pl1-f195.google.com ([209.85.214.195]:35054 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404725AbfGOOhf (ORCPT ); Mon, 15 Jul 2019 10:37:35 -0400 Received: by mail-pl1-f195.google.com with SMTP id w24so8402737plp.2 for ; Mon, 15 Jul 2019 07:37:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=d04DTAkj28sWGBD0hTaxcXYNvJEjAGRiNh/YBevkbdQ=; b=GC6kguZwzG85dZF5iWDrsveKaK2Fc4LgmUwLVCWkEfV1JlGAke0LxakzpuHBiFRaFB sYDHXQtZ71NbUDuVJ8YWKIw1R3eOc2C2ORLfAM04ltJddQI7SF38zyg1iFNWeipYVwov WMKiys6ZkCmWDq7512TerhvIp/7tNwu+a4rUE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=d04DTAkj28sWGBD0hTaxcXYNvJEjAGRiNh/YBevkbdQ=; b=U0+x7uQ1Bnx8MG9Ifw6/6o7Ye3ScOULPbIZPDzqgt+9z2VVFqb9bHrV8YnIG6zOgJ5 nh4Hjt2YLHTb+iZGnPco3gZs+t+dA4Rgkvj7poNwvSCRXUk6F5RuivsWBdn3t652r/8R muGKyyEdD3hIGMtSO7qfAd5IxNKRETIG5KURCJl1fNh2wVZX+YnegJCik/fVhShTx53W pcrwK/Sgr0Gg/OrTG6T+ZL0B0dc/TTr1m1GLDDba0cPB3mgHcuSICTXvYi5/Q5kIoZeu BeTw4BIx0boxZKYKDuVzsyNcdQxuvOC1/Uz7jOXtXZ4wihHRW902EM0rj0ltIDAFp2S1 /a7A== X-Gm-Message-State: APjAAAXPOhdNGNfKX5cLELNzSvZyA+8BVbsN6ERch1Gd/nW6Ykc/WpJo 6eUKIVoVOPfHaBUSw0oaGzQ= X-Google-Smtp-Source: APXvYqwtv2gdmgGFtRTdsHXi0t6+nEY2tSbkW03BagiSXi1mseRekjbX7fP3TCtLfUm4acXXT6gmhg== X-Received: by 2002:a17:902:aa88:: with SMTP id d8mr27314486plr.274.1563201454429; Mon, 15 Jul 2019 07:37:34 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id s66sm18381852pfs.8.2019.07.15.07.37.30 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 15 Jul 2019 07:37:33 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , Greg Kroah-Hartman , Alexey Kuznetsov , Bjorn Helgaas , Borislav Petkov , c0d1n61at3@gmail.com, "David S. Miller" , edumazet@google.com, 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 , "Paul E. McKenney" , Pavel Machek , peterz@infradead.org, "Rafael J. Wysocki" , Rasmus Villemoes , rcu@vger.kernel.org, Steven Rostedt , Tejun Heo , Thomas Gleixner , will@kernel.org, x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Subject: [PATCH 5/9] driver/core: Convert to use built-in RCU list checking (v1) Date: Mon, 15 Jul 2019 10:37:01 -0400 Message-Id: <20190715143705.117908-6-joel@joelfernandes.org> X-Mailer: git-send-email 2.22.0.510.g264f2c817a-goog In-Reply-To: <20190715143705.117908-1-joel@joelfernandes.org> References: <20190715143705.117908-1-joel@joelfernandes.org> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org list_for_each_entry_rcu has built-in RCU and lock checking. Make use of it in driver core. Acked-by: Greg Kroah-Hartman Signed-off-by: Joel Fernandes (Google) --- drivers/base/base.h | 1 + drivers/base/core.c | 10 ++++++++++ drivers/base/power/runtime.c | 15 ++++++++++----- 3 files changed, 21 insertions(+), 5 deletions(-) diff --git a/drivers/base/base.h b/drivers/base/base.h index b405436ee28e..0d32544b6f91 100644 --- a/drivers/base/base.h +++ b/drivers/base/base.h @@ -165,6 +165,7 @@ static inline int devtmpfs_init(void) { return 0; } /* Device links support */ extern int device_links_read_lock(void); extern void device_links_read_unlock(int idx); +extern int device_links_read_lock_held(void); extern int device_links_check_suppliers(struct device *dev); extern void device_links_driver_bound(struct device *dev); extern void device_links_driver_cleanup(struct device *dev); diff --git a/drivers/base/core.c b/drivers/base/core.c index da84a73f2ba6..85e82f38717f 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -68,6 +68,11 @@ void device_links_read_unlock(int idx) { srcu_read_unlock(&device_links_srcu, idx); } + +int device_links_read_lock_held(void) +{ + return srcu_read_lock_held(&device_links_srcu); +} #else /* !CONFIG_SRCU */ static DECLARE_RWSEM(device_links_lock); @@ -91,6 +96,11 @@ void device_links_read_unlock(int not_used) { up_read(&device_links_lock); } + +int device_links_read_lock_held(void) +{ + return lock_is_held(&device_links_lock); +} #endif /* !CONFIG_SRCU */ /** diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 952a1e7057c7..7a10e8379a70 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -287,7 +287,8 @@ static int rpm_get_suppliers(struct device *dev) { struct device_link *link; - list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) { + list_for_each_entry_rcu(link, &dev->links.suppliers, c_node, + device_links_read_lock_held()) { int retval; if (!(link->flags & DL_FLAG_PM_RUNTIME) || @@ -309,7 +310,8 @@ static void rpm_put_suppliers(struct device *dev) { struct device_link *link; - list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) { + list_for_each_entry_rcu(link, &dev->links.suppliers, c_node, + device_links_read_lock_held()) { if (READ_ONCE(link->status) == DL_STATE_SUPPLIER_UNBIND) continue; @@ -1640,7 +1642,8 @@ void pm_runtime_clean_up_links(struct device *dev) idx = device_links_read_lock(); - list_for_each_entry_rcu(link, &dev->links.consumers, s_node) { + list_for_each_entry_rcu(link, &dev->links.consumers, s_node, + device_links_read_lock_held()) { if (link->flags & DL_FLAG_STATELESS) continue; @@ -1662,7 +1665,8 @@ void pm_runtime_get_suppliers(struct device *dev) idx = device_links_read_lock(); - list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) + list_for_each_entry_rcu(link, &dev->links.suppliers, c_node, + device_links_read_lock_held()) if (link->flags & DL_FLAG_PM_RUNTIME) { link->supplier_preactivated = true; refcount_inc(&link->rpm_active); @@ -1683,7 +1687,8 @@ void pm_runtime_put_suppliers(struct device *dev) idx = device_links_read_lock(); - list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) + list_for_each_entry_rcu(link, &dev->links.suppliers, c_node, + device_links_read_lock_held()) if (link->supplier_preactivated) { link->supplier_preactivated = false; if (refcount_dec_not_one(&link->rpm_active)) From patchwork Mon Jul 15 14:37:02 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 1132055 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=joelfernandes.org Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="sb4sRCBH"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45nRB62HGsz9sP7 for ; Tue, 16 Jul 2019 00:44:14 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404107AbfGOOoN (ORCPT ); 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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 , "Paul E. McKenney" , Pavel Machek , peterz@infradead.org, "Rafael J. Wysocki" , Rasmus Villemoes , rcu@vger.kernel.org, Steven Rostedt , Tejun Heo , Thomas Gleixner , will@kernel.org, x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Subject: [PATCH 6/9] workqueue: Convert for_each_wq to use built-in list check (v2) Date: Mon, 15 Jul 2019 10:37:02 -0400 Message-Id: <20190715143705.117908-7-joel@joelfernandes.org> X-Mailer: git-send-email 2.22.0.510.g264f2c817a-goog In-Reply-To: <20190715143705.117908-1-joel@joelfernandes.org> References: <20190715143705.117908-1-joel@joelfernandes.org> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org list_for_each_entry_rcu now has support to check for RCU reader sections as well as lock. Just use the support in it, instead of explictly checking in the caller. Signed-off-by: Joel Fernandes (Google) --- kernel/workqueue.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 601d61150b65..e882477ebf6e 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -364,11 +364,6 @@ static void workqueue_sysfs_unregister(struct workqueue_struct *wq); !lockdep_is_held(&wq_pool_mutex), \ "RCU or wq_pool_mutex should be held") -#define assert_rcu_or_wq_mutex(wq) \ - RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \ - !lockdep_is_held(&wq->mutex), \ - "RCU or wq->mutex should be held") - #define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \ RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \ !lockdep_is_held(&wq->mutex) && \ @@ -425,9 +420,8 @@ static void workqueue_sysfs_unregister(struct workqueue_struct *wq); * ignored. */ #define for_each_pwq(pwq, wq) \ - list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \ - if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \ - else + list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node, \ + lock_is_held(&(wq->mutex).dep_map)) #ifdef CONFIG_DEBUG_OBJECTS_WORK From patchwork Mon Jul 15 14:37:03 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 1132053 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=joelfernandes.org Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="uThll7Bo"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45nRB13r7Rz9sP7 for ; Tue, 16 Jul 2019 00:44:09 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404121AbfGOOoC (ORCPT ); Mon, 15 Jul 2019 10:44:02 -0400 Received: from mail-pg1-f195.google.com ([209.85.215.195]:41529 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391989AbfGOOhn (ORCPT ); Mon, 15 Jul 2019 10:37:43 -0400 Received: by mail-pg1-f195.google.com with SMTP id q4so7808080pgj.8 for ; Mon, 15 Jul 2019 07:37:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=eTBxLnGTenFE9+XP/mevxUw30LYF4J7nnGDQ6rB2fzk=; b=uThll7BoraMqSjAErrpT4Me7GMeqrtPRWLdwCAfnN2EINbKNVrnQwWny0Uq7RfMVSW D1UfsncjiP6lcIIPxTI3DM7jVe9GIEWeYgH4cPRgvi0Vi2Lfx+Xm8cjna4+yOwHO2T9j n/4HM9YDYLCy6N041wqa0BohuR1TMRyc8xwns= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=eTBxLnGTenFE9+XP/mevxUw30LYF4J7nnGDQ6rB2fzk=; b=fXQWRCdypNaiq/6fTGg0KLhEHeRi0OmkM4sSBDZ6A4spZr9DAuGPpPk0YDVVFrFFHv Xz9ZyBqcaU3GTRm+ulaIXmpPb+yY0O5Gatfcl0ZL3A6EQJdt+6c1DQKrFDhgOMAndHGg Fq3xvPO65iDy2x4QjFfm5El+8fACf+5rS0TQ/fIOqaAf8tbtzmJvag108w+cc1WIh1FQ CNg23tIZV51l+pmDTgKoBjZHU57xkOUj5j8w4kxAFCvmixGunKNy9JQeTAcQicNpTUs6 GaN9i5QtJxttYYP0nFLWNbkUg2laO/b2+MMenO/6HZ+BA2kvVnNIcfw2y1yELxH7eumC DlEQ== X-Gm-Message-State: APjAAAWpG5TMNeSpHKRROiitowJG7keW1fFOAvNk/WJMrq25O9bao+7j c7N+Wj68QmJIwnC1RV+7BMg= X-Google-Smtp-Source: APXvYqyQVnMZHW30j+dzF3HoVSq03SIuwJyiMH4A5bHh8OI/EHwBlloUHwhc6xRgf31xUUYhBfS1bQ== X-Received: by 2002:a63:f312:: with SMTP id l18mr27687193pgh.440.1563201462557; Mon, 15 Jul 2019 07:37:42 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id s66sm18381852pfs.8.2019.07.15.07.37.38 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 15 Jul 2019 07:37:41 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , 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 , "Paul E. McKenney" , Pavel Machek , peterz@infradead.org, "Rafael J. Wysocki" , Rasmus Villemoes , rcu@vger.kernel.org, Steven Rostedt , Tejun Heo , Thomas Gleixner , will@kernel.org, x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Subject: [PATCH 7/9] x86/pci: Pass lockdep condition to pcm_mmcfg_list iterator (v1) Date: Mon, 15 Jul 2019 10:37:03 -0400 Message-Id: <20190715143705.117908-8-joel@joelfernandes.org> X-Mailer: git-send-email 2.22.0.510.g264f2c817a-goog In-Reply-To: <20190715143705.117908-1-joel@joelfernandes.org> References: <20190715143705.117908-1-joel@joelfernandes.org> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org The pcm_mmcfg_list is traversed with list_for_each_entry_rcu without a reader-lock held, because the pci_mmcfg_lock is already held. Make this known to the list macro so that it fixes new lockdep warnings that trigger due to lockdep checks added to list_for_each_entry_rcu(). Signed-off-by: Joel Fernandes (Google) Acked-by: Bjorn Helgaas Acked-by: Bjorn Helgaas Signed-off-by: Joel Fernandes (Google) --- arch/x86/pci/mmconfig-shared.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/pci/mmconfig-shared.c b/arch/x86/pci/mmconfig-shared.c index 7389db538c30..6fa42e9c4e6f 100644 --- a/arch/x86/pci/mmconfig-shared.c +++ b/arch/x86/pci/mmconfig-shared.c @@ -29,6 +29,7 @@ static bool pci_mmcfg_running_state; static bool pci_mmcfg_arch_init_failed; static DEFINE_MUTEX(pci_mmcfg_lock); +#define pci_mmcfg_lock_held() lock_is_held(&(pci_mmcfg_lock).dep_map) LIST_HEAD(pci_mmcfg_list); @@ -54,7 +55,7 @@ static void list_add_sorted(struct pci_mmcfg_region *new) struct pci_mmcfg_region *cfg; /* keep list sorted by segment and starting bus number */ - list_for_each_entry_rcu(cfg, &pci_mmcfg_list, list) { + list_for_each_entry_rcu(cfg, &pci_mmcfg_list, list, pci_mmcfg_lock_held()) { if (cfg->segment > new->segment || (cfg->segment == new->segment && cfg->start_bus >= new->start_bus)) { @@ -118,7 +119,7 @@ struct pci_mmcfg_region *pci_mmconfig_lookup(int segment, int bus) { struct pci_mmcfg_region *cfg; - list_for_each_entry_rcu(cfg, &pci_mmcfg_list, list) + list_for_each_entry_rcu(cfg, &pci_mmcfg_list, list, pci_mmcfg_lock_held()) if (cfg->segment == segment && cfg->start_bus <= bus && bus <= cfg->end_bus) return cfg; From patchwork Mon Jul 15 14:37:04 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 1132051 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=joelfernandes.org Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="XStDr0pO"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45nR9l2vq4z9sVb for ; Tue, 16 Jul 2019 00:43:55 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404178AbfGOOnx (ORCPT ); Mon, 15 Jul 2019 10:43:53 -0400 Received: from mail-pl1-f196.google.com ([209.85.214.196]:41960 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392033AbfGOOhr (ORCPT ); Mon, 15 Jul 2019 10:37:47 -0400 Received: by mail-pl1-f196.google.com with SMTP id m9so8357953pls.8 for ; Mon, 15 Jul 2019 07:37:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=5zPd11qsqBV6enPH1pgmEhMrw3DVmEsKL+rgelJGu5E=; b=XStDr0pOpAvfMPGvyaCiXhax5OpTI8omiicJPCmLonS9L7hbMWB8WbkqauDTlsAue1 /IzXyBhFpxdPHPkwfVRCjLPZYScMK7RsrUnJmmgQGxgyicRfMpFtWxfw1YpluI/oDB0w mhjDfrjf8F43ROWC4kjFdePNxqWjxG9UE7yCo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=5zPd11qsqBV6enPH1pgmEhMrw3DVmEsKL+rgelJGu5E=; b=WY6pjI5333HtlhHhNfAlFa+RVLGqea8Fh+7YjBNbGRXptH3I/keLhzTar/gmQm0vzi a1bboWAHsIXHDw1gOo0CQPBJqojVBGf7f6412expjoid89URfAe59itQASNdvKHtdQq7 07EnmPGc9wD7Lo/tucGD7cFtdJ1QVRW3LHFzQcP5mDAQGrJ6ekgb1X882RARNhDDXUvS oG1kNmNimMKy4iz0WrxdpBjC3oKbIcyudt9KV3+k0HhIRYpWt4rLaqJv0RVPrwJ6ywIV Lew7Md3QIwTeLHwCy036ePunbBHlrIoqIYgHBnO0SWeQeK6fp9xHjCntHktktVJx51iT xvsQ== X-Gm-Message-State: APjAAAUKauCTDzfUdMbZGVNlQMuB+ooNnDESxJy3nWcOEw8MjEsuviAE WUYNxkUb3DUZug2/GuZYqtQ= X-Google-Smtp-Source: APXvYqzkIpFv5vPuz81gmhFr3B+gCTSP4FKDqSNzw1vK/5n3JtNPasCMdlzt1VHFYex1IyUvrWl66Q== X-Received: by 2002:a17:902:2889:: with SMTP id f9mr27373830plb.230.1563201466638; Mon, 15 Jul 2019 07:37:46 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id s66sm18381852pfs.8.2019.07.15.07.37.42 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 15 Jul 2019 07:37:45 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , 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 , "Paul E. McKenney" , Pavel Machek , peterz@infradead.org, "Rafael J. Wysocki" , Rasmus Villemoes , rcu@vger.kernel.org, Steven Rostedt , Tejun Heo , Thomas Gleixner , will@kernel.org, x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Subject: [PATCH 8/9] acpi: Use built-in RCU list checking for acpi_ioremaps list (v1) Date: Mon, 15 Jul 2019 10:37:04 -0400 Message-Id: <20190715143705.117908-9-joel@joelfernandes.org> X-Mailer: git-send-email 2.22.0.510.g264f2c817a-goog In-Reply-To: <20190715143705.117908-1-joel@joelfernandes.org> References: <20190715143705.117908-1-joel@joelfernandes.org> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org list_for_each_entry_rcu has built-in RCU and lock checking. Make use of it for acpi_ioremaps list traversal. Signed-off-by: Joel Fernandes (Google) Acked-by: Rafael J. Wysocki --- drivers/acpi/osl.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index 9c0edf2fc0dd..2f9d0d20b836 100644 --- a/drivers/acpi/osl.c +++ b/drivers/acpi/osl.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include #include @@ -80,6 +81,7 @@ struct acpi_ioremap { static LIST_HEAD(acpi_ioremaps); static DEFINE_MUTEX(acpi_ioremap_lock); +#define acpi_ioremap_lock_held() lock_is_held(&acpi_ioremap_lock.dep_map) static void __init acpi_request_region (struct acpi_generic_address *gas, unsigned int length, char *desc) @@ -206,7 +208,7 @@ acpi_map_lookup(acpi_physical_address phys, acpi_size size) { struct acpi_ioremap *map; - list_for_each_entry_rcu(map, &acpi_ioremaps, list) + list_for_each_entry_rcu(map, &acpi_ioremaps, list, acpi_ioremap_lock_held()) if (map->phys <= phys && phys + size <= map->phys + map->size) return map; @@ -249,7 +251,7 @@ acpi_map_lookup_virt(void __iomem *virt, acpi_size size) { struct acpi_ioremap *map; - list_for_each_entry_rcu(map, &acpi_ioremaps, list) + list_for_each_entry_rcu(map, &acpi_ioremaps, list, acpi_ioremap_lock_held()) if (map->virt <= virt && virt + size <= map->virt + map->size) return map; From patchwork Mon Jul 15 14:37:05 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 1132050 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=joelfernandes.org Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="Irsk1l+c"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45nR2q6ssFz9sVD for ; Tue, 16 Jul 2019 00:37:55 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404132AbfGOOhw (ORCPT ); Mon, 15 Jul 2019 10:37:52 -0400 Received: from mail-pl1-f193.google.com ([209.85.214.193]:38491 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392141AbfGOOhw (ORCPT ); Mon, 15 Jul 2019 10:37:52 -0400 Received: by mail-pl1-f193.google.com with SMTP id az7so8392040plb.5 for ; Mon, 15 Jul 2019 07:37:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=3/Yc3rMkHMZtDKtPxvXMbpuJtYxFK974gkQSASG7nfg=; b=Irsk1l+cCvhHrnLDCclN8wIYVEkPEbD9MdUbMAfJ0kSrDpX7chroJyo2YF46UzcBkM XJuVwKS6BKM9ZHR0du6EvejWG8y2q+OPRVvdrOulKML9bNBty7xmC4DwYF/BBFtQPuLu EwiuS9bOEcElBlknIAsc95qH+foz6NeembQns= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=3/Yc3rMkHMZtDKtPxvXMbpuJtYxFK974gkQSASG7nfg=; b=kg0fyLt4RKKcjBhHYb4EY24xFl/ROTalH1kQlWQYPJwqhXn+Z6Ysw+xuXdVu0xK1DK MMKHlR4CL+ZA+Hkw3VpHzjlntwDMfHJcQtmskW/PebMKwwFeILAI7JuY/OHot1NO6JIw w2cCYOtnjORGEJPtbh1i2gT+Lnxbb0tkjqqQcAk9D7BHe8e+bTG6RZ2jbROssUVyaJKk X4Iqiq9KjHifXKgg9xF+iA+Q7Hyl9suZA3fRMOY3WxNqSlKOzyWmTJX7xDmm5zDTwSl/ U1XCJPFfQ24ivR+iMPALQglZ1j7+e+b+31piSZ9VGgwOJx2VTB8tQLnN8UY1sMINBWCj 2AlA== X-Gm-Message-State: APjAAAVA7WTTngxef/Fnq70Y7WxR3xadXk5w9p+gepGYtX6I9Bj8AsOJ 3+e9r6vCnOLgKJ153vOYt68= X-Google-Smtp-Source: APXvYqwiS/rB81iw9YBrF0TFJUziDe1TQrXSMZ4COSYLaJJSbdiihNhGfcJrAEF9RQGi29HbbCoEvQ== X-Received: by 2002:a17:902:27e6:: with SMTP id i35mr28686773plg.190.1563201470637; Mon, 15 Jul 2019 07:37:50 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id s66sm18381852pfs.8.2019.07.15.07.37.46 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 15 Jul 2019 07:37:49 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , 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 , "Paul E. McKenney" , Pavel Machek , peterz@infradead.org, "Rafael J. Wysocki" , Rasmus Villemoes , rcu@vger.kernel.org, Steven Rostedt , Tejun Heo , Thomas Gleixner , will@kernel.org, x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Subject: [PATCH 9/9] doc: Update documentation about list_for_each_entry_rcu (v1) Date: Mon, 15 Jul 2019 10:37:05 -0400 Message-Id: <20190715143705.117908-10-joel@joelfernandes.org> X-Mailer: git-send-email 2.22.0.510.g264f2c817a-goog In-Reply-To: <20190715143705.117908-1-joel@joelfernandes.org> References: <20190715143705.117908-1-joel@joelfernandes.org> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org This patch updates the documentation with information about usage of lockdep with list_for_each_entry_rcu(). Signed-off-by: Joel Fernandes (Google) --- Documentation/RCU/lockdep.txt | 15 +++++++++++---- Documentation/RCU/whatisRCU.txt | 9 ++++++++- 2 files changed, 19 insertions(+), 5 deletions(-) diff --git a/Documentation/RCU/lockdep.txt b/Documentation/RCU/lockdep.txt index da51d3068850..3d967df3a801 100644 --- a/Documentation/RCU/lockdep.txt +++ b/Documentation/RCU/lockdep.txt @@ -96,7 +96,14 @@ other flavors of rcu_dereference(). On the other hand, it is illegal to use rcu_dereference_protected() if either the RCU-protected pointer or the RCU-protected data that it points to can change concurrently. -There are currently only "universal" versions of the rcu_assign_pointer() -and RCU list-/tree-traversal primitives, which do not (yet) check for -being in an RCU read-side critical section. In the future, separate -versions of these primitives might be created. +Similar to rcu_dereference_protected, The RCU list and hlist traversal +primitives also check for whether there are called from within a reader +section. However, an optional lockdep expression can be passed to them as +the last argument in case they are called under other non-RCU protection. + +For example, the workqueue for_each_pwq() macro is implemented as follows. +It is safe to call for_each_pwq() outside a reader section but under protection +of wq->mutex: +#define for_each_pwq(pwq, wq) + list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node, + lock_is_held(&(wq->mutex).dep_map)) diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt index 7e1a8721637a..00fe77ede1e2 100644 --- a/Documentation/RCU/whatisRCU.txt +++ b/Documentation/RCU/whatisRCU.txt @@ -290,7 +290,7 @@ rcu_dereference() at any time, including immediately after the rcu_dereference(). And, again like rcu_assign_pointer(), rcu_dereference() is typically used indirectly, via the _rcu list-manipulation - primitives, such as list_for_each_entry_rcu(). + primitives, such as list_for_each_entry_rcu() [2]. [1] The variant rcu_dereference_protected() can be used outside of an RCU read-side critical section as long as the usage is @@ -305,6 +305,13 @@ rcu_dereference() a lockdep splat is emitted. See RCU/Design/Requirements/Requirements.html and the API's code comments for more details and example usage. + [2] In case the list_for_each_entry_rcu() primitive is intended + to be used outside of an RCU reader section such as when + protected by a lock, then an additional lockdep expression can be + passed as the last argument to it so that RCU lockdep checking code + knows that the dereference of the list pointers are safe. If the + indicated protection is not provided, a lockdep splat is emitted. + The following diagram shows how each API communicates among the reader, updater, and reclaimer.