Merge branch 'akpm' (patches from Andrew)

Merge yet more updates from Andrew Morton:

 - the rest of ocfs2

 - various hotfixes, mainly MM

 - quite a bit of misc stuff - drivers, fork, exec, signals, etc.

 - printk updates

 - firmware

 - checkpatch

 - nilfs2

 - more kexec stuff than usual

 - rapidio updates

 - w1 things

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (111 commits)
  ipc: delete "nr_ipc_ns"
  kcov: allow more fine-grained coverage instrumentation
  init/Kconfig: add clarification for out-of-tree modules
  config: add android config fragments
  init/Kconfig: ban CONFIG_LOCALVERSION_AUTO with allmodconfig
  relay: add global mode support for buffer-only channels
  init: allow blacklisting of module_init functions
  w1:omap_hdq: fix regression
  w1: add helper macro module_w1_family
  w1: remove need for ida and use PLATFORM_DEVID_AUTO
  rapidio/switches: add driver for IDT gen3 switches
  powerpc/fsl_rio: apply changes for RIO spec rev 3
  rapidio: modify for rev.3 specification changes
  rapidio: change inbound window size type to u64
  rapidio/idt_gen2: fix locking warning
  rapidio: fix error handling in mbox request/release functions
  rapidio/tsi721_dma: advance queue processing from transfer submit call
  rapidio/tsi721: add messaging mbox selector parameter
  rapidio/tsi721: add PCIe MRRS override parameter
  rapidio/tsi721_dma: add channel mask and queue size parameters
  ...

1 files changed, 6 insertions, 4 deletions

diff --git a/kernel/task_work.c b/kernel/task_work.c
index 6ab4842b00e8..d513051fcca2 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -29,7 +29,7 @@ task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
         struct callback_head *head;
 
         do {
-                head = ACCESS_ONCE(task->task_works);
+                head = READ_ONCE(task->task_works);
                 if (unlikely(head == &work_exited))
                         return -ESRCH;
                 work->next = head;
@@ -57,6 +57,9 @@ task_work_cancel(struct task_struct *task, task_work_func_t func)
         struct callback_head **pprev = &task->task_works;
         struct callback_head *work;
         unsigned long flags;
+
+        if (likely(!task->task_works))
+                return NULL;
         /*
          * If cmpxchg() fails we continue without updating pprev.
          * Either we raced with task_work_add() which added the
@@ -64,8 +67,7 @@ task_work_cancel(struct task_struct *task, task_work_func_t func)
          * we raced with task_work_run(), *pprev == NULL/exited.
          */
         raw_spin_lock_irqsave(&task->pi_lock, flags);
-        while ((work = ACCESS_ONCE(*pprev))) {
-                smp_read_barrier_depends();
+        while ((work = lockless_dereference(*pprev))) {
                 if (work->func != func)
                         pprev = &work->next;
                 else if (cmpxchg(pprev, work, work->next) == work)
@@ -95,7 +97,7 @@ void task_work_run(void)
                  * work_exited unless the list is empty.
                  */
                 do {
-                        work = ACCESS_ONCE(task->task_works);
+                        work = READ_ONCE(task->task_works);
                         head = !work && (task->flags & PF_EXITING) ?
                                 &work_exited : NULL;
                 } while (cmpxchg(&task->task_works, work, head) != work);