Some callers may need to make signaling decisions based on the state
of the targeted task, and that can only safely be done post adding
the task_work to the task. Split task_work_add() into:
__task_work_add() - adds the work item
__task_work_notify() - sends the notification
No functional changes in this patch.
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v5.7+
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
include/linux/task_work.h | 19 ++++++++++++++++
kernel/task_work.c | 48 +++++++++++++++++++++------------------
2 files changed, 45 insertions(+), 22 deletions(-)
diff --git a/include/linux/task_work.h b/include/linux/task_work.h
index 0fb93aafa478..7abbd8df5e13 100644
--- a/include/linux/task_work.h
+++ b/include/linux/task_work.h
@@ -5,6 +5,8 @@
#include <linux/list.h>
#include <linux/sched.h>
+extern struct callback_head work_exited;
+
typedef void (*task_work_func_t)(struct callback_head *);
static inline void
@@ -13,6 +15,21 @@ init_task_work(struct callback_head *twork, task_work_func_t func)
twork->func = func;
}
+static inline int __task_work_add(struct task_struct *task,
+ struct callback_head *work)
+{
+ struct callback_head *head;
+
+ do {
+ head = READ_ONCE(task->task_works);
+ if (unlikely(head == &work_exited))
+ return -ESRCH;
+ work->next = head;
+ } while (cmpxchg(&task->task_works, head, work) != head);
+
+ return 0;
+}
+
#define TWA_RESUME 1
#define TWA_SIGNAL 2
int task_work_add(struct task_struct *task, struct callback_head *twork, int);
@@ -20,6 +37,8 @@ int task_work_add(struct task_struct *task, struct callback_head *twork, int);
struct callback_head *task_work_cancel(struct task_struct *, task_work_func_t);
void task_work_run(void);
+void __task_work_notify(struct task_struct *task, int notify);
+
static inline void exit_task_work(struct task_struct *task)
{
task_work_run();
diff --git a/kernel/task_work.c b/kernel/task_work.c
index 5c0848ca1287..9bde81481984 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -3,7 +3,27 @@
#include <linux/task_work.h>
#include <linux/tracehook.h>
-static struct callback_head work_exited; /* all we need is ->next == NULL */
+struct callback_head work_exited = {
+ .next = NULL /* all we need is ->next == NULL */
+};
+
+void __task_work_notify(struct task_struct *task, int notify)
+{
+ unsigned long flags;
+
+ switch (notify) {
+ case TWA_RESUME:
+ set_notify_resume(task);
+ break;
+ case TWA_SIGNAL:
+ if (lock_task_sighand(task, &flags)) {
+ task->jobctl |= JOBCTL_TASK_WORK;
+ signal_wake_up(task, 0);
+ unlock_task_sighand(task, &flags);
+ }
+ break;
+ }
+}
/**
* task_work_add - ask the @task to execute @work->func()
@@ -27,29 +47,13 @@ static struct callback_head work_exited; /* all we need is ->next == NULL */
int
task_work_add(struct task_struct *task, struct callback_head *work, int notify)
{
- struct callback_head *head;
- unsigned long flags;
+ int ret;
- do {
- head = READ_ONCE(task->task_works);
- if (unlikely(head == &work_exited))
- return -ESRCH;
- work->next = head;
- } while (cmpxchg(&task->task_works, head, work) != head);
-
- switch (notify) {
- case TWA_RESUME:
- set_notify_resume(task);
- break;
- case TWA_SIGNAL:
- if (lock_task_sighand(task, &flags)) {
- task->jobctl |= JOBCTL_TASK_WORK;
- signal_wake_up(task, 0);
- unlock_task_sighand(task, &flags);
- }
- break;
- }
+ ret = __task_work_add(task, work);
+ if (unlikely(ret))
+ return ret;
+ __task_work_notify(task, notify);
return 0;
}
--
2.28.0
