Hi Waiman, Thank you for the patch! Perhaps something to improve: url: https://github.com/0day-ci/linux/commits/Waiman-Long/cgroup-Introducing-bypass-mode/20181123-030552 base: https://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git for-next smatch warnings: kernel/cgroup/cgroup.c:4893 css_create() error: we previously assumed 'parent' could be null (see line 4864) # https://github.com/0day-ci/linux/commit/8b68fd4330e043645667a5d3306398f8f88f9ff2 git remote add linux-review https://github.com/0day-ci/linux git remote update linux-review git checkout 8b68fd4330e043645667a5d3306398f8f88f9ff2 vim +/parent +4893 kernel/cgroup/cgroup.c a31f2d3ff kernel/cgroup.c Tejun Heo 2012-11-19 4840 c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4841 /** 6cd0f5bba kernel/cgroup.c Tejun Heo 2016-03-03 4842 * css_create - create a cgroup_subsys_state c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4843 * @cgrp: the cgroup new css will be associated with c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4844 * @ss: the subsys of new css c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4845 * c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4846 * Create a new css associated with @cgrp - @ss pair. On success, the new 6cd0f5bba kernel/cgroup.c Tejun Heo 2016-03-03 4847 * css is online and installed in @cgrp. This function doesn't create the 6cd0f5bba kernel/cgroup.c Tejun Heo 2016-03-03 4848 * interface files. Returns 0 on success, -errno on failure. c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4849 */ 6cd0f5bba kernel/cgroup.c Tejun Heo 2016-03-03 4850 static struct cgroup_subsys_state *css_create(struct cgroup *cgrp, 6cd0f5bba kernel/cgroup.c Tejun Heo 2016-03-03 4851 struct cgroup_subsys *ss) c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4852 { d51f39b05 kernel/cgroup.c Tejun Heo 2014-05-16 4853 struct cgroup *parent = cgroup_parent(cgrp); 8b68fd433 kernel/cgroup/cgroup.c Waiman Long 2018-11-20 4854 struct cgroup_subsys_state *parent_css = NULL; c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4855 struct cgroup_subsys_state *css; c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4856 int err; c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4857 c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4858 lockdep_assert_held(&cgroup_mutex); c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4859 8b68fd433 kernel/cgroup/cgroup.c Waiman Long 2018-11-20 4860 /* 8b68fd433 kernel/cgroup/cgroup.c Waiman Long 2018-11-20 4861 * As cgroup may be in bypass mode, need to skip over ancestor 8b68fd433 kernel/cgroup/cgroup.c Waiman Long 2018-11-20 4862 * cgroups with NULL CSS. 8b68fd433 kernel/cgroup/cgroup.c Waiman Long 2018-11-20 4863 */ 8b68fd433 kernel/cgroup/cgroup.c Waiman Long 2018-11-20 @4864 for (; parent && !parent_css; parent = cgroup_parent(parent)) ^^^^^^^^^^^^^^^^^^^^^ 8b68fd433 kernel/cgroup/cgroup.c Waiman Long 2018-11-20 4865 parent_css = cgroup_css(parent, ss); When we exit this loop it means either parent is NULL or parent_css is non-NULL. 8b68fd433 kernel/cgroup/cgroup.c Waiman Long 2018-11-20 4866 1fed1b2e3 kernel/cgroup.c Tejun Heo 2014-05-16 4867 css = ss->css_alloc(parent_css); e7e15b87f kernel/cgroup.c Tejun Heo 2016-06-21 4868 if (!css) e7e15b87f kernel/cgroup.c Tejun Heo 2016-06-21 4869 css = ERR_PTR(-ENOMEM); c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4870 if (IS_ERR(css)) 6cd0f5bba kernel/cgroup.c Tejun Heo 2016-03-03 4871 return css; c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4872 8b68fd433 kernel/cgroup/cgroup.c Waiman Long 2018-11-20 4873 init_and_link_css(css, ss, cgrp, parent_css); a2bed8209 kernel/cgroup.c Tejun Heo 2014-05-04 4874 2aad2a86f kernel/cgroup.c Tejun Heo 2014-09-24 4875 err = percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL); c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4876 if (err) 3eb59ec64 kernel/cgroup.c Li Zefan 2014-03-18 4877 goto err_free_css; c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4878 cf780b7dc kernel/cgroup.c Vladimir Davydov 2015-08-03 4879 err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL); 15a4c835e kernel/cgroup.c Tejun Heo 2014-05-04 4880 if (err < 0) b00c52dae kernel/cgroup.c Wenwei Tao 2016-05-13 4881 goto err_free_css; 15a4c835e kernel/cgroup.c Tejun Heo 2014-05-04 4882 css->id = err; c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4883 15a4c835e kernel/cgroup.c Tejun Heo 2014-05-04 4884 /* @css is ready to be brought online now, make it visible */ 1fed1b2e3 kernel/cgroup.c Tejun Heo 2014-05-16 4885 list_add_tail_rcu(&css->sibling, &parent_css->children); 15a4c835e kernel/cgroup.c Tejun Heo 2014-05-04 4886 cgroup_idr_replace(&ss->css_idr, css, css->id); c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4887 c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4888 err = online_css(css); c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4889 if (err) 1fed1b2e3 kernel/cgroup.c Tejun Heo 2014-05-16 4890 goto err_list_del; 944196278 kernel/cgroup.c Tejun Heo 2014-03-19 4891 c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4892 if (ss->broken_hierarchy && !ss->warned_broken_hierarchy && d51f39b05 kernel/cgroup.c Tejun Heo 2014-05-16 @4893 cgroup_parent(parent)) { ^^^^^^ We dereference parent inside the function, but I don't know for sure if this is reachable when "parent" is NULL. ed3d261b5 kernel/cgroup.c Joe Perches 2014-04-25 4894 pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n", c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4895 current->comm, current->pid, ss->name); c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4896 if (!strcmp(ss->name, "memory")) ed3d261b5 kernel/cgroup.c Joe Perches 2014-04-25 4897 pr_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n"); c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4898 ss->warned_broken_hierarchy = true; c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4899 } c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4900 6cd0f5bba kernel/cgroup.c Tejun Heo 2016-03-03 4901 return css; c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4902 1fed1b2e3 kernel/cgroup.c Tejun Heo 2014-05-16 4903 err_list_del: 1fed1b2e3 kernel/cgroup.c Tejun Heo 2014-05-16 4904 list_del_rcu(&css->sibling); 3eb59ec64 kernel/cgroup.c Li Zefan 2014-03-18 4905 err_free_css: 8f53470ba kernel/cgroup/cgroup.c Tejun Heo 2018-04-26 4906 list_del_rcu(&css->rstat_css_node); 8f36aaec9 kernel/cgroup/cgroup.c Tejun Heo 2018-03-14 4907 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn); 8f36aaec9 kernel/cgroup/cgroup.c Tejun Heo 2018-03-14 4908 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork); 6cd0f5bba kernel/cgroup.c Tejun Heo 2016-03-03 4909 return ERR_PTR(err); c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4910 } c81c925ad kernel/cgroup.c Tejun Heo 2013-12-06 4911 --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
