Merge branch 'akpm' (patches from Andrew Morton)

Merge first patch-bomb from Andrew Morton:
 - Some pidns/fork/exec tweaks
 - OCFS2 updates
 - Most of MM - there remain quite a few memcg parts which depend on
   pending core cgroups changes.  Which might have been already merged -
   I'll check tomorrow...
 - Various misc stuff all over the place
 - A few block bits which I never got around to sending to Jens -
   relatively minor things.
 - MAINTAINERS maintenance
 - A small number of lib/ updates
 - checkpatch updates
 - epoll
 - firmware/dmi-scan
 - Some kprobes work for S390
 - drivers/rtc updates
 - hfsplus feature work
 - vmcore feature work
 - rbtree upgrades
 - AOE updates
 - pktcdvd cleanups
 - PPS
 - memstick
 - w1
 - New "inittmpfs" feature, which does the obvious
 - More IPC work from Davidlohr.

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (303 commits)
  lz4: fix compression/decompression signedness mismatch
  ipc: drop ipc_lock_check
  ipc, shm: drop shm_lock_check
  ipc: drop ipc_lock_by_ptr
  ipc, shm: guard against non-existant vma in shmdt(2)
  ipc: document general ipc locking scheme
  ipc,msg: drop msg_unlock
  ipc: rename ids->rw_mutex
  ipc,shm: shorten critical region for shmat
  ipc,shm: cleanup do_shmat pasta
  ipc,shm: shorten critical region for shmctl
  ipc,shm: make shmctl_nolock lockless
  ipc,shm: introduce shmctl_nolock
  ipc: drop ipcctl_pre_down
  ipc,shm: shorten critical region in shmctl_down
  ipc,shm: introduce lockless functions to obtain the ipc object
  initmpfs: use initramfs if rootfstype= or root= specified
  initmpfs: make rootfs use tmpfs when CONFIG_TMPFS enabled
  initmpfs: move rootfs code from fs/ramfs/ to init/
  initmpfs: move bdi setup from init_rootfs to init_ramfs
  ...

1 files changed, 38 insertions, 2 deletions

diff --git a/kernel/task_work.c b/kernel/task_work.c
index 65bd3c92d6f..8727032e3a6 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -4,6 +4,23 @@
 
 static struct callback_head work_exited; /* all we need is ->next == NULL */
 
+/**
+ * task_work_add - ask the @task to execute @work->func()
+ * @task: the task which should run the callback
+ * @work: the callback to run
+ * @notify: send the notification if true
+ *
+ * Queue @work for task_work_run() below and notify the @task if @notify.
+ * Fails if the @task is exiting/exited and thus it can't process this @work.
+ * Otherwise @work->func() will be called when the @task returns from kernel
+ * mode or exits.
+ *
+ * This is like the signal handler which runs in kernel mode, but it doesn't
+ * try to wake up the @task.
+ *
+ * RETURNS:
+ * 0 if succeeds or -ESRCH.
+ */
 int
 task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
 {
@@ -21,11 +38,22 @@ task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
 	return 0;
 }
 
+/**
+ * task_work_cancel - cancel a pending work added by task_work_add()
+ * @task: the task which should execute the work
+ * @func: identifies the work to remove
+ *
+ * Find the last queued pending work with ->func == @func and remove
+ * it from queue.
+ *
+ * RETURNS:
+ * The found work or NULL if not found.
+ */
 struct callback_head *
 task_work_cancel(struct task_struct *task, task_work_func_t func)
 {
 	struct callback_head **pprev = &task->task_works;
-	struct callback_head *work = NULL;
+	struct callback_head *work;
 	unsigned long flags;
 	/*
 	 * If cmpxchg() fails we continue without updating pprev.
@@ -35,7 +63,7 @@ task_work_cancel(struct task_struct *task, task_work_func_t func)
 	 */
 	raw_spin_lock_irqsave(&task->pi_lock, flags);
 	while ((work = ACCESS_ONCE(*pprev))) {
-		read_barrier_depends();
+		smp_read_barrier_depends();
 		if (work->func != func)
 			pprev = &work->next;
 		else if (cmpxchg(pprev, work, work->next) == work)
@@ -46,6 +74,14 @@ task_work_cancel(struct task_struct *task, task_work_func_t func)
 	return work;
 }
 
+/**
+ * task_work_run - execute the works added by task_work_add()
+ *
+ * Flush the pending works. Should be used by the core kernel code.
+ * Called before the task returns to the user-mode or stops, or when
+ * it exits. In the latter case task_work_add() can no longer add the
+ * new work after task_work_run() returns.
+ */
 void task_work_run(void)
 {
 	struct task_struct *task = current;