Currently, the only method to detach a task from a cgroup is moving it to others. It looks not natrual to me.
Inspired by cgroup_subtree_control_write(), this patch introduce allow user to at-detach a process to/from a cgroup by echo "+/-pid" to cgroup.procs. In addition, we keep the old method to allow user echo "pid" without "+/-" to cgroup.procs as a attaching behavior. Signed-off-by: Dongsheng Yang <[email protected]> --- >From v1: *Sorry for a incorrect comment in v1. kernel/cgroup.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 59 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 7dc8788..a4bb604 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2348,6 +2348,43 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp, return ret; } +/** + * cgroup_detach_task - detach a task or a whole threadgroup to a cgroup + * @src_cgrp: the cgroup to detach from + * @leader: the task or the leader of the threadgroup to be attached + * @threadgroup: attach the whole threadgroup? + * + * Call holding cgroup_mutex and threadgroup_lock of @leader. + */ +static int cgroup_detach_task(struct cgroup *src_cgrp __maybe_unused, + struct task_struct *leader, bool threadgroup) +{ + LIST_HEAD(preloaded_csets); + struct task_struct *task; + int ret; + + /* look up all src csets */ + down_read(&css_set_rwsem); + rcu_read_lock(); + task = leader; + do { + cgroup_migrate_add_src(task_css_set(task), &cgrp_dfl_root.cgrp, + &preloaded_csets); + if (!threadgroup) + break; + } while_each_thread(leader, task); + rcu_read_unlock(); + up_read(&css_set_rwsem); + + /* prepare dst csets and commit */ + ret = cgroup_migrate_prepare_dst(&cgrp_dfl_root.cgrp, &preloaded_csets); + if (!ret) + ret = cgroup_migrate(&cgrp_dfl_root.cgrp, leader, threadgroup); + + cgroup_migrate_finish(&preloaded_csets); + return ret; +} + /* * Find the task_struct of the task to attach by vpid and pass it along to the * function to attach either it or all tasks in its threadgroup. Will lock @@ -2361,8 +2398,25 @@ static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf, struct cgroup *cgrp; pid_t pid; int ret; + bool attach; - if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0) + /* + * Parse input - pid prefixed with either + or -. + */ + buf = strstrip(buf); + if (*buf == '+') { + attach = true; + buf++; + } else if (*buf == '-') { + attach = false; + buf++; + } else { + if (!isdigit(*buf)) + return -EINVAL; + attach = true; + } + + if (kstrtoint(buf, 0, &pid) || pid < 0) return -EINVAL; cgrp = cgroup_kn_lock_live(of->kn); @@ -2426,7 +2480,10 @@ retry_find_task: } } - ret = cgroup_attach_task(cgrp, tsk, threadgroup); + if (attach) + ret = cgroup_attach_task(cgrp, tsk, threadgroup); + else + ret = cgroup_detach_task(cgrp, tsk, threadgroup); threadgroup_unlock(tsk); -- 1.8.4.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
