From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: [merged] llist-fix-simplify-llist_add-and-llist_add_batch.patch removed from -mm tree Date: Mon, 15 Jul 2013 13:49:37 -0700 Message-ID: <51e46061.HPSVKt98ATVxMDtg%akpm@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from mail.linuxfoundation.org ([140.211.169.12]:49301 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753484Ab3GOUti (ORCPT ); Mon, 15 Jul 2013 16:49:38 -0400 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: mm-commits@vger.kernel.org, ying.huang@intel.com, viro@zeniv.linux.org.uk, ebiederm@xmission.com, dhowells@redhat.com, avagin@openvz.org, a.p.zijlstra@chello.nl, oleg@redhat.com Subject: [merged] llist-fix-simplify-llist_add-and-llist_add_batch.patch removed from -mm tree To: oleg@redhat.com,a.p.zijlstra@chello.nl,avagin@openvz.org,dhowells@redhat.com,ebiederm@xmission.com,viro@zeniv.linux.org.uk,ying.huang@intel.com,mm-commits@vger.kernel.org From: akpm@linux-foundation.org Date: Mon, 15 Jul 2013 13:49:37 -0700 The patch titled Subject: llist: fix/simplify llist_add() and llist_add_batch() has been removed from the -mm tree. Its filename was llist-fix-simplify-llist_add-and-llist_add_batch.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Oleg Nesterov Subject: llist: fix/simplify llist_add() and llist_add_batch() 1. This is mostly theoretical, but llist_add*() need ACCESS_ONCE(). Otherwise it is not guaranteed that the first cmpxchg() uses the same value for old_entry and new_last->next. 2. These helpers cache the result of cmpxchg() and read the initial value of head->first before the main loop. I do not think this makes sense. In the likely case cmpxchg() succeeds, otherwise it doesn't hurt to reload head->first. I think it would be better to simplify the code and simply read ->first before cmpxchg(). Signed-off-by: Oleg Nesterov Cc: Al Viro Cc: Andrey Vagin Cc: "Eric W. Biederman" Cc: David Howells Cc: Huang Ying Cc: Peter Zijlstra Signed-off-by: Andrew Morton --- include/linux/llist.h | 15 +++++---------- lib/llist.c | 15 +++++---------- 2 files changed, 10 insertions(+), 20 deletions(-) diff -puN include/linux/llist.h~llist-fix-simplify-llist_add-and-llist_add_batch include/linux/llist.h --- a/include/linux/llist.h~llist-fix-simplify-llist_add-and-llist_add_batch +++ a/include/linux/llist.h @@ -151,18 +151,13 @@ static inline struct llist_node *llist_n */ static inline bool llist_add(struct llist_node *new, struct llist_head *head) { - struct llist_node *entry, *old_entry; + struct llist_node *first; - entry = head->first; - for (;;) { - old_entry = entry; - new->next = entry; - entry = cmpxchg(&head->first, old_entry, new); - if (entry == old_entry) - break; - } + do { + new->next = first = ACCESS_ONCE(head->first); + } while (cmpxchg(&head->first, first, new) != first); - return old_entry == NULL; + return !first; } /** diff -puN lib/llist.c~llist-fix-simplify-llist_add-and-llist_add_batch lib/llist.c --- a/lib/llist.c~llist-fix-simplify-llist_add-and-llist_add_batch +++ a/lib/llist.c @@ -39,18 +39,13 @@ bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last, struct llist_head *head) { - struct llist_node *entry, *old_entry; + struct llist_node *first; - entry = head->first; - for (;;) { - old_entry = entry; - new_last->next = entry; - entry = cmpxchg(&head->first, old_entry, new_first); - if (entry == old_entry) - break; - } + do { + new_last->next = first = ACCESS_ONCE(head->first); + } while (cmpxchg(&head->first, first, new_first) != first); - return old_entry == NULL; + return !first; } EXPORT_SYMBOL_GPL(llist_add_batch); _ Patches currently in -mm which might be from oleg@redhat.com are mm-mempolicy-fix-mbind_range-vma_adjust-interaction.patch include-linux-schedh-dont-use-task-pid-tgid-in-same_thread_group-has_group_leader_pid.patch lockdep-introduce-lock_acquire_exclusive-shared-helper-macros.patch lglock-update-lockdep-annotations-to-report-recursive-local-locks.patch mm-mempolicy-turn-vma_set_policy-into-vma_dup_policy.patch kernel-wide-fix-missing-validations-on-__get-__put-__copy_to-__copy_from_user.patch autofs4-allow-autofs-to-work-outside-the-initial-pid-namespace.patch autofs4-translate-pids-to-the-right-namespace-for-the-daemon.patch signals-eventpoll-set-saved_sigmask-at-the-start.patch move-exit_task_namespaces-outside-of-exit_notify-fix.patch