linux-kernel - [PATCH-tip v5 20/21] sched, TP-futex: Make wake_up

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Date:   Fri,  3 Feb 2017 13:03:53 -0500
From:   Waiman Long <longman@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jonathan Corbet <corbet@....net>
Cc:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Mike Galbraith <umgwanakikbuti@...il.com>,
        Scott J Norton <scott.norton@....com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH-tip v5 20/21] sched, TP-futex: Make wake_up_q() return wakeup count

Unlike wake_up_process(), wake_up_q() doesn't tell us how many
tasks have been woken up. This information can sometimes be useful
for tracking purpose. So wake_up_q() is now modified to return that
information.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 include/linux/sched/wake_q.h | 2 +-
 kernel/futex.c               | 8 +++-----
 kernel/sched/core.c          | 6 ++++--
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/linux/sched/wake_q.h b/include/linux/sched/wake_q.h
index 9a32f17..2b2bc9d 100644
--- a/include/linux/sched/wake_q.h
+++ b/include/linux/sched/wake_q.h
@@ -49,6 +49,6 @@ static inline void wake_q_init(struct wake_q_head *head)
 
 extern void wake_q_add(struct wake_q_head *head,
 		       struct task_struct *task);
-extern void wake_up_q(struct wake_q_head *head);
+extern int wake_up_q(struct wake_q_head *head);
 
 #endif /* _LINUX_SCHED_WAKE_Q_H */
diff --git a/kernel/futex.c b/kernel/futex.c
index 16c63b8..6bf5304 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -4257,11 +4257,9 @@ static int futex_unlock(u32 __user *uaddr, unsigned int flags,
 out_put_key:
 	put_futex_key(&key);
 	if (owner) {
-		/*
-		 * No error would have happened if owner defined.
-		 */
-		wake_up_q(&wake_q);
-		return ret ? ret : 1;
+		int cnt = wake_up_q(&wake_q);
+
+		return ret ? ret : cnt;
 	}
 
 	return ret;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 679093d..668a094 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -452,9 +452,10 @@ void wake_q_add(struct wake_q_head *head, struct task_struct *task)
 	head->lastp = &node->next;
 }
 
-void wake_up_q(struct wake_q_head *head)
+int wake_up_q(struct wake_q_head *head)
 {
 	struct wake_q_node *node = head->first;
+	int wakecnt = 0;
 
 	while (node != WAKE_Q_TAIL) {
 		struct task_struct *task;
@@ -469,9 +470,10 @@ void wake_up_q(struct wake_q_head *head)
 		 * wake_up_process() implies a wmb() to pair with the queueing
 		 * in wake_q_add() so as not to miss wakeups.
 		 */
-		wake_up_process(task);
+		wakecnt += wake_up_process(task);
 		put_task_struct(task);
 	}
+	return wakecnt;
 }
 
 /*
-- 
1.8.3.1