The 'trywake' name was renamed to simply 'wake',
update the comment.
Signed-off-by: Davidlohr Bueso <[email protected]>
---
kernel/exit.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/exit.c b/kernel/exit.c
index 0b81b26a872a..6cc6cc485d07 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -243,7 +243,7 @@ void rcuwait_wake_up(struct rcuwait *w)
/*
* Order condition vs @task, such that everything prior to the load
* of @task is visible. This is the condition as to why the user called
- * rcuwait_trywake() in the first place. Pairs with set_current_state()
+ * rcuwait_wake() in the first place. Pairs with set_current_state()
* barrier (A) in rcuwait_wait_event().
*
* WAIT WAKE
--
2.16.4
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 <[email protected]>
---
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
With both the increased use of swait and kvm no longer using
it, we can reword some of the comments. While removing Linus'
valid rant, I've also cared to explicitly mention that swait
is very different than regular wait. In addition it is
mentioned against using swait in favor of the regular flavor.
Signed-off-by: Davidlohr Bueso <[email protected]>
---
include/linux/swait.h | 23 +++++------------------
1 file changed, 5 insertions(+), 18 deletions(-)
diff --git a/include/linux/swait.h b/include/linux/swait.h
index 73e06e9986d4..6e5b5d0e64fd 100644
--- a/include/linux/swait.h
+++ b/include/linux/swait.h
@@ -9,23 +9,10 @@
#include <asm/current.h>
/*
- * BROKEN wait-queues.
- *
- * These "simple" wait-queues are broken garbage, and should never be
- * used. The comments below claim that they are "similar" to regular
- * wait-queues, but the semantics are actually completely different, and
- * every single user we have ever had has been buggy (or pointless).
- *
- * A "swake_up_one()" only wakes up _one_ waiter, which is not at all what
- * "wake_up()" does, and has led to problems. In other cases, it has
- * been fine, because there's only ever one waiter (kvm), but in that
- * case gthe whole "simple" wait-queue is just pointless to begin with,
- * since there is no "queue". Use "wake_up_process()" with a direct
- * pointer instead.
- *
- * While these are very similar to regular wait queues (wait.h) the most
- * important difference is that the simple waitqueue allows for deterministic
- * behaviour -- IOW it has strictly bounded IRQ and lock hold times.
+ * Simple waitqueues are semantically very different to regular wait queues
+ * (wait.h). The most important difference is that the simple waitqueue allows
+ * for deterministic behaviour -- IOW it has strictly bounded IRQ and lock hold
+ * times.
*
* Mainly, this is accomplished by two things. Firstly not allowing swake_up_all
* from IRQ disabled, and dropping the lock upon every wakeup, giving a higher
@@ -39,7 +26,7 @@
* sleeper state.
*
* - the !exclusive mode; because that leads to O(n) wakeups, everything is
- * exclusive.
+ * exclusive. As such swait_wake_up_one will only ever awake _one_ waiter.
*
* - custom wake callback functions; because you cannot give any guarantees
* about random code. This also allows swait to be used in RT, such that
--
2.16.4
On 2020-03-20 01:55:25 [-0700], Davidlohr Bueso wrote:
> 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.
Wouldn't it make sense to return wake_up_process() return value to know
if a change of state occurred or not?
Sebastian