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

Davidlohr Bueso
2020-03-20T08:56:42Z

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