[brauner:clone_into_cgroup 2/3] kernel/cgroup/cgroup.c:5930:3: warning: ignoring return value of 'mutex_lock_killable', declared with attribute warn_unused_result

[brauner:clone_into_cgroup 2/3] kernel/cgroup/cgroup.c:5930:3: warning: ignoring return value of 'mutex_lock_killable', declared with attribute warn_unused_result

[kbuild test robot]

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tree:   https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git clone_into_cgroup
head:   fc5f569c2dad303ee4cc0d0625ce234e73bcda44
commit: 51e007bbe308fa2c70119c65d6845a2af72e533b [2/3] clone3: allow spawning processes into cgroups
config: m68k-allmodconfig (attached as .config)
compiler: m68k-linux-gcc (GCC) 7.5.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout 51e007bbe308fa2c70119c65d6845a2af72e533b
        # save the attached .config to linux build tree
        GCC_VERSION=7.5.0 make.cross ARCH=m68k 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   kernel/cgroup/cgroup.c: In function 'cgroup_css_set_fork':
>> kernel/cgroup/cgroup.c:5930:3: warning: ignoring return value of 'mutex_lock_killable', declared with attribute warn_unused_result [-Wunused-result]
      mutex_lock_killable(&cgroup_mutex);
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

vim +/mutex_lock_killable +5930 kernel/cgroup/cgroup.c

  5902	
  5903	/**
  5904	 * cgroup_css_set_fork - find or create a css_set for a child process
  5905	 * @parent: the parent of the child process
  5906	 * @kargs: the arguments passed to create the child process
  5907	 *
  5908	 * This functions finds or creates a new css_set which the child
  5909	 * process will be attached to in cgroup_post_fork(). By default,
  5910	 * the child process will be given the same css_set as its parent.
  5911	 *
  5912	 * If CLONE_INTO_CGROUP is specified this function will try to find an
  5913	 * existing css_set which includes the request cgorup and if not create
  5914	 * new css_set that the child will be attached to. After this function
  5915	 * returns when CLONE_INTO_CGROUP is used we will hold a reference to the
  5916	 * target cgroup. This is done so we can check whether the cgroup is
  5917	 * still alive right before we enter fork()'s point of no return.
  5918	 */
  5919	static int cgroup_css_set_fork(struct task_struct *parent,
  5920				       struct kernel_clone_args *kargs)
  5921		__acquires(&cgroup_mutex) __acquires(&cgroup_threadgroup_rwsem)
  5922	{
  5923		int ret;
  5924		struct cgroup *dst_cgrp = NULL, *src_cgrp;
  5925		struct css_set *cset;
  5926		struct super_block *sb;
  5927		struct file *f;
  5928	
  5929		if (kargs->flags & CLONE_INTO_CGROUP)
> 5930			mutex_lock_killable(&cgroup_mutex);
  5931	
  5932		cgroup_threadgroup_change_begin(parent);
  5933	
  5934		spin_lock_irq(&css_set_lock);
  5935		cset = task_css_set(parent);
  5936		get_css_set(cset);
  5937		spin_unlock_irq(&css_set_lock);
  5938	
  5939		if (!(kargs->flags & CLONE_INTO_CGROUP)) {
  5940			kargs->cset = cset;
  5941			return 0;
  5942		}
  5943	
  5944		f = fget_raw(kargs->cgroup);
  5945		if (!f) {
  5946			ret = -EBADF;
  5947			goto err;
  5948		}
  5949		sb = f->f_path.dentry->d_sb;
  5950	
  5951		dst_cgrp = cgroup_get_from_file(f);
  5952		if (IS_ERR(dst_cgrp)) {
  5953			ret = PTR_ERR(dst_cgrp);
  5954			goto err;
  5955		}
  5956	
  5957		spin_lock_irq(&css_set_lock);
  5958		src_cgrp = task_cgroup_from_root(parent, &cgrp_dfl_root);
  5959		spin_unlock_irq(&css_set_lock);
  5960	
  5961		ret = cgroup_attach_permissions(src_cgrp, dst_cgrp, sb,
  5962						!!(kargs->flags & CLONE_THREAD));
  5963		if (ret)
  5964			goto err;
  5965	
  5966		kargs->cset = find_css_set(cset, dst_cgrp);
  5967		if (!kargs->cset) {
  5968			ret = -ENOMEM;
  5969			goto err;
  5970		}
  5971	
  5972		if (cgroup_is_dead(dst_cgrp)) {
  5973			ret = -ENODEV;
  5974			goto err;
  5975		}
  5976	
  5977		put_css_set(cset);
  5978		fput(f);
  5979		kargs->cgrp = dst_cgrp;
  5980		return ret;
  5981	
  5982	err:
  5983		cgroup_threadgroup_change_end(parent);
  5984		mutex_unlock(&cgroup_mutex);
  5985		if (f)
  5986			fput(f);
  5987		if (dst_cgrp)
  5988			cgroup_put(dst_cgrp);
  5989		put_css_set(cset);
  5990		return ret;
  5991	}
  5992	

---
0-DAY kernel test infrastructure                 Open Source Technology Center
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org Intel Corporation

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