[PATCH 17/15] rcuwait: Inform rcuwait_wake_up() users if a wakeup was attempted

From: Davidlohr Bueso <dave@stgolabs.net>
To: tglx@linutronix.de
Cc: arnd@arndb.de, balbi@kernel.org, bhelgaas@google.com,
	bigeasy@linutronix.de, dave@stgolabs.net, davem@davemloft.net,
	gregkh@linuxfoundation.org, joel@joelfernandes.org,
	kurt.schwemmer@microsemi.com, kvalo@codeaurora.org,
	linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-usb@vger.kernel.org, linux-wireless@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org, logang@deltatee.com,
	mingo@kernel.org, mpe@ellerman.id.au, netdev@vger.kernel.org,
	oleg@redhat.com, paulmck@kernel.org, peterz@infradead.org,
	rdunlap@infradead.org, rostedt@goodmis.org,
	torvalds@linux-foundation.org, will@kernel.org,
	Davidlohr Bueso <dbueso@suse.de>
Subject: [PATCH 17/15] rcuwait: Inform rcuwait_wake_up() users if a wakeup was attempted
Date: Fri, 20 Mar 2020 01:55:25 -0700	[thread overview]
Message-ID: <20200320085527.23861-2-dave@stgolabs.net> (raw)
In-Reply-To: <20200320085527.23861-1-dave@stgolabs.net>

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@suse.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

