From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755621AbbLEAOx (ORCPT ); Fri, 4 Dec 2015 19:14:53 -0500 Received: from e37.co.us.ibm.com ([32.97.110.158]:44781 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755427AbbLEAOv (ORCPT ); Fri, 4 Dec 2015 19:14:51 -0500 X-IBM-Helo: d03dlp02.boulder.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 1/4] list: Use WRITE_ONCE() when adding to lists and hlists Date: Fri, 4 Dec 2015 16:15:28 -0800 Message-Id: <1449274531-27043-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 2.5.2 In-Reply-To: <20151205001505.GA26649@linux.vnet.ibm.com> References: <20151205001505.GA26649@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15120500-0025-0000-0000-00001F4E9EC9 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Code that does lockless emptiness testing of non-RCU lists is relying on the list-addition code to write the list head's ->next pointer atomically. This commit therefore adds WRITE_ONCE() to list-addition pointer stores that could affect the head's ->next pointer. Reported-by: Dmitry Vyukov Signed-off-by: Paul E. McKenney --- include/linux/list.h | 8 ++++---- lib/list_debug.c | 2 +- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/include/linux/list.h b/include/linux/list.h index 993395a2e55c..d7e31fe398b3 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -42,7 +42,7 @@ static inline void __list_add(struct list_head *new, next->prev = new; new->next = next; new->prev = prev; - prev->next = new; + WRITE_ONCE(prev->next, new); } #else extern void __list_add(struct list_head *new, @@ -642,7 +642,7 @@ static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h) n->next = first; if (first) first->pprev = &n->next; - h->first = n; + WRITE_ONCE(h->first, n); n->pprev = &h->first; } @@ -653,14 +653,14 @@ static inline void hlist_add_before(struct hlist_node *n, n->pprev = next->pprev; n->next = next; next->pprev = &n->next; - *(n->pprev) = n; + WRITE_ONCE(*(n->pprev), n); } static inline void hlist_add_behind(struct hlist_node *n, struct hlist_node *prev) { n->next = prev->next; - prev->next = n; + WRITE_ONCE(prev->next, n); n->pprev = &prev->next; if (n->next) diff --git a/lib/list_debug.c b/lib/list_debug.c index c24c2f7e296f..3859bf63561c 100644 --- a/lib/list_debug.c +++ b/lib/list_debug.c @@ -37,7 +37,7 @@ void __list_add(struct list_head *new, next->prev = new; new->next = next; new->prev = prev; - prev->next = new; + WRITE_ONCE(prev->next, new); } EXPORT_SYMBOL(__list_add); -- 2.5.2