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Subject[PATCH 3/3] Revert "task_work: remove fifo ordering guarantee"
This reverts commit c82199061009d1561e31e17fca5e47a87cb7ff4c.

Now that fput() can't abuse ->task_works list, we can restore the FIFO
ordering. Yes, currently there are no in-kernel users which need this,
but I think task_work_add() will have more users and FIFO makes more
sense if (unlike fput/mntput) the callbacks change the task's state.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/task_work.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/kernel/task_work.c b/kernel/task_work.c
index 53fa971..8727032 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -18,8 +18,6 @@ static struct callback_head work_exited; /* all we need is ->next == NULL */
* This is like the signal handler which runs in kernel mode, but it doesn't
* try to wake up the @task.
*
- * Note: there is no ordering guarantee on works queued here.
- *
* RETURNS:
* 0 if succeeds or -ESRCH.
*/
@@ -110,6 +108,16 @@ void task_work_run(void)
raw_spin_unlock_wait(&task->pi_lock);
smp_mb();

+ /* Reverse the list to run the works in fifo order */
+ head = NULL;
+ do {
+ next = work->next;
+ work->next = head;
+ head = work;
+ work = next;
+ } while (work);
+
+ work = head;
do {
next = work->next;
work->func(work);
--
2.4.3


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