linux-kernel - [PATCH 17/15] rcuwait: Inform rcuwait_wake

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Date:   Fri, 20 Mar 2020 01:55:25 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     tglx@...utronix.de
Cc:     arnd@...db.de, balbi@...nel.org, bhelgaas@...gle.com,
        bigeasy@...utronix.de, dave@...olabs.net, davem@...emloft.net,
        gregkh@...uxfoundation.org, joel@...lfernandes.org,
        kurt.schwemmer@...rosemi.com, kvalo@...eaurora.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-wireless@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, logang@...tatee.com,
        mingo@...nel.org, mpe@...erman.id.au, netdev@...r.kernel.org,
        oleg@...hat.com, paulmck@...nel.org, peterz@...radead.org,
        rdunlap@...radead.org, rostedt@...dmis.org,
        torvalds@...ux-foundation.org, will@...nel.org,
        Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH 17/15] rcuwait: Inform rcuwait_wake_up() users if a wakeup was attempted

Let the caller know if wake_up_process() was actually called or not;
some users can use this information for ad-hoc. Of course returning
true does not guarantee that wake_up_process() actually woke anything
up.

Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
---
 include/linux/rcuwait.h |  2 +-
 kernel/exit.c           | 10 ++++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/linux/rcuwait.h b/include/linux/rcuwait.h
index 6e8798458091..3f83b9a12ad3 100644
--- a/include/linux/rcuwait.h
+++ b/include/linux/rcuwait.h
@@ -24,7 +24,7 @@ static inline void rcuwait_init(struct rcuwait *w)
 	w->task = NULL;
 }
 
-extern void rcuwait_wake_up(struct rcuwait *w);
+extern bool rcuwait_wake_up(struct rcuwait *w);
 
 /*
  * The caller is responsible for locking around rcuwait_wait_event(),
diff --git a/kernel/exit.c b/kernel/exit.c
index 6cc6cc485d07..b0bb0a8ec4b1 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -234,9 +234,10 @@ void release_task(struct task_struct *p)
 		goto repeat;
 }
 
-void rcuwait_wake_up(struct rcuwait *w)
+bool rcuwait_wake_up(struct rcuwait *w)
 {
 	struct task_struct *task;
+	bool ret = false;
 
 	rcu_read_lock();
 
@@ -254,10 +255,15 @@ void rcuwait_wake_up(struct rcuwait *w)
 	smp_mb(); /* (B) */
 
 	task = rcu_dereference(w->task);
-	if (task)
+	if (task) {
 		wake_up_process(task);
+	        ret = true;
+	}
 	rcu_read_unlock();
+
+	return ret;
 }
+EXPORT_SYMBOL_GPL(rcuwait_wake_up);
 
 /*
  * Determine if a process group is "orphaned", according to the POSIX
-- 
2.16.4