The patch titled
doc: atomic_add_unless() doesn't imply mb() on failure
has been removed from the -mm tree. Its filename was
doc-atomic_add_unless-doesnt-imply-mb-on-failure.patch
This patch was dropped because we don't seem to be able to agree on it
------------------------------------------------------
Subject: doc: atomic_add_unless() doesn't imply mb() on failure
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Most implementations of atomic_add_unless() can fail (return 0) after the
first atomic_read() (before cmpxchg). In that case we have a compiler
barrier only.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
Documentation/atomic_ops.txt | 3 ++-
Documentation/memory-barriers.txt | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
diff -puN Documentation/atomic_ops.txt~doc-atomic_add_unless-doesnt-imply-mb-on-failure Documentation/atomic_ops.txt
--- a/Documentation/atomic_ops.txt~doc-atomic_add_unless-doesnt-imply-mb-on-failure
+++ a/Documentation/atomic_ops.txt
@@ -137,7 +137,8 @@ If the atomic value v is not equal to u,
returns non zero. If v is equal to u then it returns zero. This is done as
an atomic operation.
-atomic_add_unless requires explicit memory barriers around the operation.
+atomic_add_unless requires explicit memory barriers around the operation
+unless it fails (returns 0).
atomic_inc_not_zero, equivalent to atomic_add_unless(v, 1, 0)
diff -puN Documentation/memory-barriers.txt~doc-atomic_add_unless-doesnt-imply-mb-on-failure Documentation/memory-barriers.txt
--- a/Documentation/memory-barriers.txt~doc-atomic_add_unless-doesnt-imply-mb-on-failure
+++ a/Documentation/memory-barriers.txt
@@ -1492,7 +1492,7 @@ about the state (old or new) implies an
atomic_dec_and_test();
atomic_sub_and_test();
atomic_add_negative();
- atomic_add_unless();
+ atomic_add_unless(); /* when succeeds (returns 1) */
test_and_set_bit();
test_and_clear_bit();
test_and_change_bit();
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
git-dvb.patch
fix-refrigerator-vs-thaw_process-race.patch
doc-atomic_add_unless-doesnt-imply-mb-on-failure.patch
clone-flag-clone_parent_tidptr-leaves-invalid-results-in-memory.patch
allow-access-to-proc-pid-fd-after-setuid.patch
freezer-task-exit_state-should-be-treated-as-bolean.patch
softlockup-trivial-s-99-max_rt_prio.patch
fix-race-between-proc_get_inode-and-remove_proc_entry.patch
getrusage-fill-ru_inblock-and-ru_oublock-fields-if-possible.patch
futex-restartable-futex_wait.patch
futex-restartable-futex_wait-fix.patch
add-support-for-deferrable-timers-respun.patch
add-support-for-deferrable-timers-respun-tidy.patch
add-support-for-deferrable-timers-respun-fix.patch
add-a-new-deferrable-delayed-work-init.patch
reimplement-flush_workqueue.patch
implement-flush_work.patch
implement-flush_work-sanity.patch
implement-flush_work_keventd.patch
flush_workqueue-use-preempt_disable-to-hold-off-cpu-hotplug.patch
flush_cpu_workqueue-dont-flush-an-empty-worklist.patch
aio-use-flush_work.patch
kblockd-use-flush_work.patch
relayfs-use-flush_keventd_work.patch
tg3-use-flush_keventd_work.patch
e1000-use-flush_keventd_work.patch
libata-use-flush_work.patch
phy-use-flush_work.patch
call-cpu_chain-with-cpu_down_failed-if-cpu_down_prepare-failed.patch
slab-use-cpu_lock_.patch
workqueue-fix-freezeable-workqueues-implementation.patch
workqueue-fix-flush_workqueue-vs-cpu_dead-race.patch
workqueue-dont-clear-cwq-thread-until-it-exits.patch
workqueue-dont-migrate-pending-works-from-the-dead-cpu.patch
workqueue-kill-run_scheduled_work.patch
workqueue-dont-save-interrupts-in-run_workqueue.patch
workqueue-make-cancel_rearming_delayed_workqueue-work-on-idle-dwork.patch
workqueue-introduce-cpu_singlethread_map.patch
workqueue-introduce-workqueue_struct-singlethread.patch
workqueue-make-init_workqueues-__init.patch
make-queue_delayed_work-friendly-to-flush_fork.patch
unify-queue_delayed_work-and-queue_delayed_work_on.patch
workqueue-introduce-wq_per_cpu-helper.patch
make-cancel_rearming_delayed_work-work-on-any-workqueue-not-just-keventd_wq.patch
ipvs-flush-defense_work-before-module-unload.patch
workqueue-kill-noautorel-works.patch
worker_thread-dont-play-with-signals.patch
worker_thread-fix-racy-try_to_freeze-usage.patch
zap_other_threads-remove-unneeded-exit_signal-change.patch
slab-shutdown-cache_reaper-when-cpu-goes-down.patch
unify-flush_work-flush_work_keventd-and-rename-it-to-cancel_work_sync.patch
____call_usermodehelper-dont-flush_signals.patch
freezer-read-pf_borrowed_mm-in-a-nonracy-way.patch
freezer-close-theoretical-race-between-refrigerator-and-thaw_tasks.patch
freezer-remove-pf_nofreeze-from-rcutorture-thread.patch
freezer-remove-pf_nofreeze-from-bluetooth-threads.patch
freezer-add-try_to_freeze-calls-to-all-kernel-threads.patch
freezer-fix-vfork-problem.patch
freezer-take-kernel_execve-into-consideration.patch
kthread-dont-depend-on-work-queues-take-2.patch
kthread-dont-depend-on-work-queues-take-2-fix.patch
change-reparent_to_init-to-reparent_to_kthreadd.patch
nlmclnt_recovery-dont-use-clone_sighand.patch
usbatm_heavy_init-dont-use-clone_sighand.patch
wait_for_helper-remove-unneeded-do_sigaction.patch
worker_thread-dont-play-with-sigchld-and-numa-policy.patch
change-kernel-threads-to-ignore-signals-instead-of-blocking-them.patch
fix-kthread_create-vs-freezer-theoretical-race.patch
fix-kthread_create-vs-freezer-theoretical-race-dont-be-obnoxious.patch
fix-pf_nofreeze-and-freezeable-race-2.patch
freezer-document-task_lock-in-thaw_process.patch
move-frozen_process-to-kernel-power-processc.patch
remvoe-kthread_bind-call-from-_cpu_down.patch
dont-init-pgrp-and-__session-in-init_signals.patch
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