From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 18 May 2020 10:30:09 +0000 (-0400)
Subject: rcuwait: avoid lockdep splats from rcuwait_active()
X-Git-Tag: microblaze-v5.10~663^2~66
X-Git-Url: http://git.monstr.eu/?a=commitdiff_plain;h=febd668d375caf13a7fcd93b3498366854de854a;p=linux-2.6-microblaze.git

rcuwait: avoid lockdep splats from rcuwait_active()

rcuwait_active only returns whether w->task is not NULL.  This is
exactly one of the usecases that are mentioned in the documentation
for rcu_access_pointer() where it is correct to bypass lockdep checks.

This avoids a splat from kvm_vcpu_on_spin().

Reported-by: Wanpeng Li <kernellwp@gmail.com>
Tested-by: Wanpeng Li <kernellwp@gmail.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/include/linux/rcuwait.h b/include/linux/rcuwait.h
index c1414ce44abc..61c56cca95c4 100644
--- a/include/linux/rcuwait.h
+++ b/include/linux/rcuwait.h
@@ -31,7 +31,7 @@ static inline void rcuwait_init(struct rcuwait *w)
  */
 static inline int rcuwait_active(struct rcuwait *w)
 {
-	return !!rcu_dereference(w->task);
+	return !!rcu_access_pointer(w->task);
 }
 
 extern int rcuwait_wake_up(struct rcuwait *w);