Subject: + llist-fix-simplify-llist_add-and-llist_add_batch.patch added to -mm tree
To: oleg@xxxxxxxxxx,a.p.zijlstra@xxxxxxxxx,avagin@xxxxxxxxxx,dhowells@xxxxxxxxxx,ebiederm@xxxxxxxxxxxx,viro@xxxxxxxxxxxxxxxxxx,ying.huang@xxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 18 Jun 2013 14:00:43 -0700
The patch titled
Subject: llist: fix/simplify llist_add() and llist_add_batch()
has been added to the -mm tree. Its filename is
llist-fix-simplify-llist_add-and-llist_add_batch.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
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
linux-next.patch
fput-task_work_add-can-fail-if-the-caller-has-passed-exit_task_work-fix.patch
posix_cpu_timer-consolidate-expiry-time-type.patch
posix_cpu_timers-consolidate-timer-list-cleanups.patch
posix_cpu_timers-consolidate-expired-timers-check.patch
posix-timers-correctly-get-dying-task-time-sample-in-posix_cpu_timer_schedule.patch
posix_timers-fix-racy-timer-delta-caching-on-task-exit.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
fput-turn-list_head-delayed_fput_list-into-llist_head.patch
llist-fix-simplify-llist_add-and-llist_add_batch.patch
llist-llist_add-can-use-llist_add_batch.patch
vfree-dont-schedule-free_work-if-llist_add-returns-false.patch
kernel-sysc-do_sysinfo-use-get_monotonic_boottime.patch
autofs4-allow-autofs-to-work-outside-the-initial-pid-namespace.patch
autofs4-translate-pids-to-the-right-namespace-for-the-daemon.patch
ptrace-x86-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
ptrace-powerpc-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
ptrace-arm-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
ptrace-sh-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
ptrace-revert-prepare-to-fix-racy-accesses-on-task-breakpoints.patch
ptrace-x86-simplify-the-disable-logic-in-ptrace_write_dr7.patch
ptrace-x86-dont-delay-disable-till-second-pass-in-ptrace_write_dr7.patch
ptrace-x86-introduce-ptrace_register_breakpoint.patch
ptrace-x86-ptrace_write_dr7-should-create-bp-if-disabled.patch
ptrace-x86-cleanup-ptrace_set_debugreg.patch
ptrace-ptrace_detach-should-do-flush_ptrace_hw_breakpointchild.patch
ptrace-x86-flush_ptrace_hw_breakpoint-shoule-clear-the-virtual-debug-registers.patch
x86-kill-tif_debug.patch
ptrace-add-ability-to-get-set-signal-blocked-mask.patch
usermodehelper-kill-the-sub_info-path-check.patch
coredump-format_corename-can-leak-cn-corename.patch
coredump-introduce-cn_vprintf.patch
coredump-cn_vprintf-has-no-reason-to-call-vsnprintf-twice.patch
coredump-kill-cn_escape-introduce-cn_esc_printf.patch
coredump-kill-call_count-add-core_name_size.patch
coredump-%-at-the-end-shouldnt-bypass-core_uses_pid-logic.patch
coredump-%-at-the-end-shouldnt-bypass-core_uses_pid-logic-fix.patch
fs-execc-de_thread-use-change_pid-rather-than-detach_pid-attach_pid.patch
move-exit_task_namespaces-outside-of-exit_notify-fix.patch
exitc-unexport-__set_special_pids.patch
fs-proc-uptimec-uptime_proc_show-use-get_monotonic_boottime.patch
kernel-forkc-copy_process-unify-clone_thread-or-thread_group_leader-code.patch
kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists.patch
kernel-forkc-copy_process-consolidate-the-lockless-clone_thread-checks.patch
fs-execc-do_execve_common-use-current_user.patch
fs-execc-de_thread-mt-exec-should-update-real_start_time.patch
wait-introduce-wait_event_commonwq-condition-state-timeout.patch
wait-introduce-wait_event_commonwq-condition-state-timeout-checkpatch-fixes.patch
wait-introduce-prepare_to_wait_event.patch
wait-introduce-prepare_to_wait_event-checkpatch-fixes.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
