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

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Message-ID: <1c21533e-347e-4faa-b6d3-385ec0edf0cd@virtuozzo.com>
Date: Wed, 24 Dec 2025 12:43:24 +0800
From: Pavel Tikhomirov <ptikhomirov@...tuozzo.com>
To: kernel test robot <lkp@...el.com>, Tejun Heo <tj@...nel.org>
Cc: oe-kbuild-all@...ts.linux.dev, Johannes Weiner <hannes@...xchg.org>,
 Michal Koutný <mkoutny@...e.com>, cgroups@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] cgroup-v2/freezer: Print information about
 unfreezable process

linux$ git diff
diff --git a/kernel/cgroup/freezer.c b/kernel/cgroup/freezer.c
index 3880ed400879..21a0edc4a97d 100644
--- a/kernel/cgroup/freezer.c
+++ b/kernel/cgroup/freezer.c
@@ -4,6 +4,7 @@
 #include <linux/sysctl.h>
 #include <linux/sched.h>
 #include <linux/sched/task.h>
+#include <linux/sched/task_stack.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/debug.h>
 
the above should fix that.

On 12/24/25 04:58, kernel test robot wrote:
> 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: s390-randconfig-r071-20251224 (https://download.01.org/0day-ci/archive/20251224/202512240409.06R0khaZ-lkp@intel.com/config)
> compiler: s390-linux-gcc (GCC) 8.5.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251224/202512240409.06R0khaZ-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@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202512240409.06R0khaZ-lkp@intel.com/
> 
> All errors (new ones prefixed by >>):
> 
>    kernel/cgroup/freezer.c: In function 'warn_freeze_timeout_task':
>>> kernel/cgroup/freezer.c:374:7: error: implicit declaration of function 'try_get_task_stack'; did you mean 'tryget_task_struct'? [-Werror=implicit-function-declaration]
>      if (!try_get_task_stack(task))
>           ^~~~~~~~~~~~~~~~~~
>           tryget_task_struct
>>> kernel/cgroup/freezer.c:377:2: error: implicit declaration of function 'put_task_stack'; did you mean 'put_task_struct'? [-Werror=implicit-function-declaration]
>      put_task_stack(task);
>      ^~~~~~~~~~~~~~
>      put_task_struct
>    cc1: some warnings being treated as errors
> 
> Kconfig warnings: (for reference only)
>    WARNING: unmet direct dependencies detected for CAN_DEV
>    Depends on [n]: NETDEVICES [=n] && CAN [=y]
>    Selected by [y]:
>    - CAN [=y] && NET [=y]
> 
> 
> vim +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	
> 

-- 
Best regards, Pavel Tikhomirov
Senior Software Developer, Virtuozzo.