Subject: [merged] llist-fix-simplify-llist_add-and-llist_add_batch.patch removed from -mm tree
To: oleg@xxxxxxxxxx,a.p.zijlstra@xxxxxxxxx,avagin@xxxxxxxxxx,dhowells@xxxxxxxxxx,ebiederm@xxxxxxxxxxxx,viro@xxxxxxxxxxxxxxxxxx,ying.huang@xxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
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 <oleg@xxxxxxxxxx>
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 <oleg@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrey Vagin <avagin@xxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxxx 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
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