Re: [PATCH 2/2] cgroup-v2/freezer: Print information about unfreezable process

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

Hi Pavel,

kernel test robot noticed the following build errors:

[auto build test ERROR on tj-cgroup/for-next]
[also build test ERROR on linus/master v6.19-rc2 next-20251219]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Pavel-Tikhomirov/cgroup-v2-freezer-allow-freezing-with-kthreads/20251223-182826
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git for-next
patch link:    https://lore.kernel.org/r/20251223102124.738818-4-ptikhomirov%40virtuozzo.com
patch subject: [PATCH 2/2] cgroup-v2/freezer: Print information about unfreezable process
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20251224/202512240240.TCvafX5S-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/20251224/202512240240.TCvafX5S-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/202512240240.TCvafX5S-lkp@intel.com/

All errors (new ones prefixed by >>):

>> kernel/cgroup/freezer.c:374:7: error: call to undeclared function 'try_get_task_stack'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     374 |         if (!try_get_task_stack(task))
         |              ^
   kernel/cgroup/freezer.c:374:7: note: did you mean 'tryget_task_struct'?
   include/linux/sched/task.h:120:35: note: 'tryget_task_struct' declared here
     120 | static inline struct task_struct *tryget_task_struct(struct task_struct *t)
         |                                   ^
>> kernel/cgroup/freezer.c:377:2: error: call to undeclared function 'put_task_stack'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     377 |         put_task_stack(task);
         |         ^
   kernel/cgroup/freezer.c:377:2: note: did you mean 'put_task_struct'?
   include/linux/sched/task.h:128:20: note: 'put_task_struct' declared here
     128 | static inline void put_task_struct(struct task_struct *t)
         |                    ^
   2 errors generated.


vim +/try_get_task_stack +374 kernel/cgroup/freezer.c

   357	
   358	static void warn_freeze_timeout_task(struct cgroup *cgrp, int timeout,
   359					     struct task_struct *task)
   360	{
   361		char *buf __free(kfree) = NULL;
   362		pid_t tgid;
   363	
   364		buf = kmalloc(PATH_MAX, GFP_KERNEL);
   365		if (!buf)
   366			return;
   367	
   368		if (cgroup_path(cgrp, buf, PATH_MAX) < 0)
   369			return;
   370	
   371		tgid = task_pid_nr_ns(task, &init_pid_ns);
   372		pr_warn("Freeze of %s took %ld sec, due to unfreezable process %d:%s.\n",
   373			buf, timeout / USEC_PER_SEC, tgid, task->comm);
 > 374		if (!try_get_task_stack(task))
   375			return;
   376		show_stack(task, NULL, KERN_WARNING);
 > 377		put_task_stack(task);
   378	}
   379	

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