From c7aab1a7c52b82d9afd7e03c398eb03dc2aa0507 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 1 Apr 2021 19:53:29 -0600
Subject: [PATCH] task_work: add helper for more targeted task_work canceling
The only exported helper we have right now is task_work_cancel(), which
cancels any task_work from a given task where func matches the queued
work item. This is a bit too coarse for some use cases. Add a
task_work_cancel_match() that allows to more specifically target
individual work items outside of purely the callback function used.
task_work_cancel() can be trivially implemented on top of that, hence do
so.
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
include/linux/task_work.h | 2 ++
kernel/task_work.c | 35 ++++++++++++++++++++++++++++-------
2 files changed, 30 insertions(+), 7 deletions(-)
diff --git a/include/linux/task_work.h b/include/linux/task_work.h
index 0d848a1e9e62f..5b8a93f288bb4 100644
--- a/include/linux/task_work.h
+++ b/include/linux/task_work.h
@@ -22,6 +22,8 @@ enum task_work_notify_mode {
int task_work_add(struct task_struct *task, struct callback_head *twork,
enum task_work_notify_mode mode);
+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(struct task_struct *, task_work_func_t);
void task_work_run(void);
diff --git a/kernel/task_work.c b/kernel/task_work.c
index 9cde961875c0a..e9316198c64bf 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -59,18 +59,17 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
}
/**
- * task_work_cancel - cancel a pending work added by task_work_add()
+ * task_work_cancel_match - 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.
+ * @match: match function to call
*
* RETURNS:
* The found work or NULL if not found.
*/
struct callback_head *
-task_work_cancel(struct task_struct *task, task_work_func_t func)
+task_work_cancel_match(struct task_struct *task,
+ bool (*match)(struct callback_head *, void *data),
+ void *data)
{
struct callback_head **pprev = &task->task_works;
struct callback_head *work;
@@ -86,7 +85,7 @@ task_work_cancel(struct task_struct *task, task_work_func_t func)
*/
raw_spin_lock_irqsave(&task->pi_lock, flags);
while ((work = READ_ONCE(*pprev))) {
- if (work->func != func)
+ if (!match(work, data))
pprev = &work->next;
else if (cmpxchg(pprev, work, work->next) == work)
break;
@@ -96,6 +95,28 @@ task_work_cancel(struct task_struct *task, task_work_func_t func)
return work;
}
+static bool task_work_func_match(struct callback_head *cb, void *data)
+{
+ return cb->func == data;
+}
+
+/**
+ * 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)
+{
+ return task_work_cancel_match(task, task_work_func_match, func);
+}
+
/**
* task_work_run - execute the works added by task_work_add()
*
--
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