Thanks, Arnd. Tested on top of 1eccf02fb8d5 with CONFIG_PREEMPT_RCU=y:
CONFIG_RT_MUTEXES=y: build passes CONFIG_RT_MUTEXES=n: fails without this patch, passes with it The failure is in tree_stall.h, where rt_mutex_owner() is used before tree_plugin.h includes rtmutex_common.h. This matches the reported failure, and the added include fixes it. Reviewed-by: Kunwu Chan <[email protected]> Tested-by: Kunwu Chan <[email protected]> Thanks, Kunwu On Fri, Sep 25, 2026 at 9:39 PM Arnd Bergmann <[email protected]> wrote: > > From: Arnd Bergmann <[email protected]> > > 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 <[email protected]> > --- > 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 >
