[tip: locking/core] futex: Fix PREEMPT_RT build

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     4d38167330910ddb15b1add5b5cef835677a29fd
Gitweb:        https://git.kernel.org/tip/4d38167330910ddb15b1add5b5cef835677a29fd
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Fri, 15 Oct 2021 12:05:59 +02:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 19 Oct 2021 17:27:05 +02:00

futex: Fix PREEMPT_RT build

Mike reported that rcuwait went walk-about and is causing failures on
the PREEMPT_RT builds, restore it.

Reported-by: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 kernel/futex/futex.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index 948fcf3..040ae42 100644
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -5,6 +5,10 @@
 #include <linux/futex.h>
 #include <linux/sched/wake_q.h>
 
+#ifdef CONFIG_PREEMPT_RT
+#include <linux/rcuwait.h>
+#endif
+
 #include <asm/futex.h>
 
 /*