linux-kernel - [PATCH v2 1/3] sched/core: Export wake

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Message-Id: <1535316795-21560-2-git-send-email-longman@redhat.com>
Date:   Sun, 26 Aug 2018 16:53:13 -0400
From:   Waiman Long <longman@...hat.com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dave Chinner <david@...morbit.com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH v2 1/3] sched/core: Export wake_q functions to kernel modules

The use of wake_q_add() and wake_up_q() functions help to do task wakeup
without holding lock can help to reduce lock hold time. They should be
available to kernel modules as well.

A new task_in_wake_q() inline function is also added to check if the
given task is in a wake_q.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 include/linux/sched/wake_q.h | 5 +++++
 kernel/sched/core.c          | 2 ++
 2 files changed, 7 insertions(+)

diff --git a/include/linux/sched/wake_q.h b/include/linux/sched/wake_q.h
index 10b19a192b2d..902bf1228d32 100644
--- a/include/linux/sched/wake_q.h
+++ b/include/linux/sched/wake_q.h
@@ -47,6 +47,11 @@ static inline void wake_q_init(struct wake_q_head *head)
 	head->lastp = &head->first;
 }
 
+static inline bool task_in_wake_q(struct task_struct *task)
+{
+	return READ_ONCE(task->wake_q.next) != NULL;
+}
+
 extern void wake_q_add(struct wake_q_head *head,
 		       struct task_struct *task);
 extern void wake_up_q(struct wake_q_head *head);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 625bc9897f62..d90a2930b8ce 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -420,6 +420,7 @@ void wake_q_add(struct wake_q_head *head, struct task_struct *task)
 	*head->lastp = node;
 	head->lastp = &node->next;
 }
+EXPORT_SYMBOL_GPL(wake_q_add);
 
 void wake_up_q(struct wake_q_head *head)
 {
@@ -442,6 +443,7 @@ void wake_up_q(struct wake_q_head *head)
 		put_task_struct(task);
 	}
 }
+EXPORT_SYMBOL_GPL(wake_up_q);
 
 /*
  * resched_curr - mark rq's current task 'to be rescheduled now'.
-- 
2.18.0