[PATCH 1/4] task_work: add task_work_pending() helper

[Jens Axboe <axboe@xxxxxxxxx>]

Various callsites currently check current->task_works != NULL to know
when to run work. Add a helper that we use internally for that. This is
in preparation for also not running if exit queue has been queued.

Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
 include/linux/task_work.h | 16 ++++++++++++++--
 kernel/task_work.c        |  2 +-
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/include/linux/task_work.h b/include/linux/task_work.h
index bd9a6a91c097..088538590e65 100644
--- a/include/linux/task_work.h
+++ b/include/linux/task_work.h
@@ -15,11 +15,23 @@ init_task_work(struct callback_head *twork, task_work_func_t func)
 
 int task_work_add(struct task_struct *task, struct callback_head *twork, bool);
 struct callback_head *task_work_cancel(struct task_struct *, task_work_func_t);
-void task_work_run(void);
+void __task_work_run(void);
+
+static inline bool task_work_pending(void)
+{
+	return current->task_works;
+}
+
+static inline void task_work_run(void)
+{
+	if (task_work_pending())
+		__task_work_run();
+}
 
 static inline void exit_task_work(struct task_struct *task)
 {
-	task_work_run();
+	/* must always run to install exit work */
+	__task_work_run();
 }
 
 #endif	/* _LINUX_TASK_WORK_H */
diff --git a/kernel/task_work.c b/kernel/task_work.c
index 825f28259a19..9620333423a3 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -87,7 +87,7 @@ task_work_cancel(struct task_struct *task, task_work_func_t func)
  * 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)
+void __task_work_run(void)
 {
 	struct task_struct *task = current;
 	struct callback_head *work, *head, *next;
-- 
2.26.0