RCU, workqueue: Implement rcu_work
There are cases where RCU callback needs to be bounced to a sleepable
context. This is currently done by the RCU callback queueing a work
item, which can be cumbersome to write and confusing to read.
This patch introduces rcu_work, a workqueue work variant which gets
executed after a RCU grace period, and converts the open coded
bouncing in fs/aio and kernel/cgroup.
v3: Dropped queue_rcu_work_on(). Documented rcu grace period behavior
after queue_rcu_work().
v2: Use rcu_barrier() instead of synchronize_rcu() to wait for
completion of previously queued rcu callback as per Paul.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index bc0cda1..d026f8f 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -13,6 +13,7 @@
#include <linux/threads.h>
#include <linux/atomic.h>
#include <linux/cpumask.h>
+#include <linux/rcupdate.h>
struct workqueue_struct;
@@ -120,6 +121,14 @@ struct delayed_work {
int cpu;
};
+struct rcu_work {
+ struct work_struct work;
+ struct rcu_head rcu;
+
+ /* target workqueue ->rcu uses to queue ->work */
+ struct workqueue_struct *wq;
+};
+
/**
* struct workqueue_attrs - A struct for workqueue attributes.
*
@@ -151,6 +160,11 @@ static inline struct delayed_work *to_delayed_work(struct work_struct *work)
return container_of(work, struct delayed_work, work);
}
+static inline struct rcu_work *to_rcu_work(struct work_struct *work)
+{
+ return container_of(work, struct rcu_work, work);
+}
+
struct execute_work {
struct work_struct work;
};
@@ -266,6 +280,12 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
#define INIT_DEFERRABLE_WORK_ONSTACK(_work, _func) \
__INIT_DELAYED_WORK_ONSTACK(_work, _func, TIMER_DEFERRABLE)
+#define INIT_RCU_WORK(_work, _func) \
+ INIT_WORK(&(_work)->work, (_func))
+
+#define INIT_RCU_WORK_ONSTACK(_work, _func) \
+ INIT_WORK_ONSTACK(&(_work)->work, (_func))
+
/**
* work_pending - Find out whether a work item is currently pending
* @work: The work item in question
@@ -447,6 +467,7 @@ extern bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
struct delayed_work *work, unsigned long delay);
extern bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
struct delayed_work *dwork, unsigned long delay);
+extern bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork);
extern void flush_workqueue(struct workqueue_struct *wq);
extern void drain_workqueue(struct workqueue_struct *wq);
@@ -463,6 +484,8 @@ extern bool flush_delayed_work(struct delayed_work *dwork);
extern bool cancel_delayed_work(struct delayed_work *dwork);
extern bool cancel_delayed_work_sync(struct delayed_work *dwork);
+extern bool flush_rcu_work(struct rcu_work *rwork);
+
extern void workqueue_set_max_active(struct workqueue_struct *wq,
int max_active);
extern struct work_struct *current_work(void);