[PATCH] rcu: include rtmutex_common.h in tree_stall.h

[Arnd Bergmann]

From: Arnd Bergmann <arnd@xxxxxxxx>

The added call to rt_mutex_owner() makes this fail to build in
some configurations:

In file included from kernel/rcu/tree.c:5121:
kernel/rcu/tree_stall.h:333:8: error: call to undeclared function 'rt_mutex_owner'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
  333 |                         if (rt_mutex_owner(&rnp->boost_mtx.rtmutex) == t)
      |                             ^
kernel/rcu/tree_stall.h:333:48: error: comparison between pointer and integer ('int' and 'struct task_struct *') [-Werror,-Wpointer-integer-compare]
  333 |                         if (rt_mutex_owner(&rnp->boost_mtx.rtmutex) == t)
      |                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^  ~
In file included from kernel/rcu/tree.c:5124:
In file included from kernel/rcu/tree_plugin.h:14:
kernel/rcu/../locking/rtmutex_common.h:231:35: error: conflicting types for 'rt_mutex_owner'
  231 | static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
      |                                   ^
kernel/rcu/tree_stall.h:333:8: note: previous implicit declaration is here
  333 |                         if (rt_mutex_owner(&rnp->boost_mtx.rtmutex) == t)
      |                             ^

There are already a couple of inclusions of "../locking/rtmutex_common.h",
so assume this is safe to do here.

Fixes: 1eccf02fb8d5 ("rcu: Add running and boosted indications to RCU task stall dump")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
I wonder if it would be better to either move the rt_mutex_owner()
definition into a global header like include/linux/rtmutex.h, or to
move the code out of tree_stall.h into a .c file, as this feels like a
layering violation.
---
 kernel/rcu/tree_stall.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 5dded1e89197..803a56af3259 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -12,6 +12,7 @@
 #include <linux/rcu_notifier.h>
 #include <linux/smp.h>
 #include <linux/rtmutex.h>
+#include "../locking/rtmutex_common.h"
 
 //////////////////////////////////////////////////////////////////////////////
 //
-- 
2.53.0