[paulmckrcu:dev.2026.09.09a 42/56] kernel/rcu/tree_stall.h:332:48: warning: comparison between pointer and integer ('int' and 'struct task_struct *')

[kernel test robot <lkp@intel.com>]

tree:   https://github.com/paulmckrcu/linux dev.2026.09.09a
head:   d61d9b5dd56c6cf72b70bb5fb52b213ead9f7765
commit: e33488c41be623f7c7ef5b8763e20c45f1364d1c [42/56] rcu: Add running and boosted indications to RCU task stall dump
config: powerpc-tqm8xx_defconfig (https://download.01.org/0day-ci/archive/20260912/202609120047.u7Af769s-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260912/202609120047.u7Af769s-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202609120047.u7Af769s-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from kernel/rcu/tree.c:5112:
   kernel/rcu/tree_stall.h:332:8: error: call to undeclared function 'rt_mutex_owner'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     332 |                         if (rt_mutex_owner(&rnp->boost_mtx.rtmutex) == t)
         |                             ^
>> kernel/rcu/tree_stall.h:332:48: warning: comparison between pointer and integer ('int' and 'struct task_struct *') [-Wpointer-integer-compare]
     332 |                         if (rt_mutex_owner(&rnp->boost_mtx.rtmutex) == t)
         |                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^  ~
   In file included from kernel/rcu/tree.c:5115:
   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:332:8: note: previous implicit declaration is here
     332 |                         if (rt_mutex_owner(&rnp->boost_mtx.rtmutex) == t)
         |                             ^
   1 warning and 2 errors generated.


vim +332 kernel/rcu/tree_stall.h

   311	
   312	/*
   313	 * Report out the state of a not-running task that is stalling the
   314	 * current RCU grace period.
   315	 */
   316	static int check_slow_task(struct task_struct *t, void *arg)
   317	{
   318		struct rcu_node *rnp;
   319		struct rcu_stall_chk_rdr *rscrp = arg;
   320	
   321		if (task_curr(t))
   322			return -EBUSY; // It is running, so decline to inspect it.
   323		rscrp->nesting = t->rcu_read_lock_nesting;
   324		rscrp->rs = t->rcu_read_unlock_special;
   325		rscrp->on_blkd_list = !list_empty(&t->rcu_node_entry);
   326		rscrp->rcu_rdr_running = task_curr(t);
   327		rscrp->rcu_rdr_boosted = 0;
   328		if (rscrp->on_blkd_list) {
   329			rnp = READ_ONCE(t->rcu_blocked_node);
   330			raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
   331			if (rnp == READ_ONCE(t->rcu_blocked_node)) {
 > 332				if (rt_mutex_owner(&rnp->boost_mtx.rtmutex) == t)
   333					rscrp->rcu_rdr_boosted = 1;
   334			} else {
   335				rscrp->rcu_rdr_boosted = 2;
   336			}
   337			raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
   338		}
   339		return 0;
   340	}
   341	

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