[tip: perf/urgent] task_work: Introduce task_work_cancel() again

[tip-bot2 for Frederic Weisbecker]

The following commit has been merged into the perf/urgent branch of tip:

Commit-ID:     74e45974c966fdecafb7149edb08a2f210e7ab60
Gitweb:        https://git.kernel.org/tip/74e45974c966fdecafb7149edb08a2f210e7ab60
Author:        Frederic Weisbecker <frederic@xxxxxxxxxx>
AuthorDate:    Fri, 21 Jun 2024 11:15:59 +02:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 25 Jun 2024 10:43:37 +02:00

task_work: Introduce task_work_cancel() again

Re-introduce task_work_cancel(), this time to cancel an actual callback
and not *any* callback pointing to a given function. This is going to be
needed for perf events event freeing.

Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240621091601.18227-3-frederic@xxxxxxxxxx
---
 include/linux/task_work.h |  1 +
 kernel/task_work.c        | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/include/linux/task_work.h b/include/linux/task_work.h
index 23ab01a..26b8a47 100644
--- a/include/linux/task_work.h
+++ b/include/linux/task_work.h
@@ -31,6 +31,7 @@ int task_work_add(struct task_struct *task, struct callback_head *twork,
 struct callback_head *task_work_cancel_match(struct task_struct *task,
 	bool (*match)(struct callback_head *, void *data), void *data);
 struct callback_head *task_work_cancel_func(struct task_struct *, task_work_func_t);
+bool task_work_cancel(struct task_struct *task, struct callback_head *cb);
 void task_work_run(void);
 
 static inline void exit_task_work(struct task_struct *task)
diff --git a/kernel/task_work.c b/kernel/task_work.c
index 54ac240..2134ac8 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -136,6 +136,30 @@ task_work_cancel_func(struct task_struct *task, task_work_func_t func)
 	return task_work_cancel_match(task, task_work_func_match, func);
 }
 
+static bool task_work_match(struct callback_head *cb, void *data)
+{
+	return cb == data;
+}
+
+/**
+ * task_work_cancel - cancel a pending work added by task_work_add()
+ * @task: the task which should execute the work
+ * @cb: the callback to remove if queued
+ *
+ * Remove a callback from a task's queue if queued.
+ *
+ * RETURNS:
+ * True if the callback was queued and got cancelled, false otherwise.
+ */
+bool task_work_cancel(struct task_struct *task, struct callback_head *cb)
+{
+	struct callback_head *ret;
+
+	ret = task_work_cancel_match(task, task_work_match, cb);
+
+	return ret == cb;
+}
+
 /**
  * task_work_run - execute the works added by task_work_add()
  *