From: Tejun Heo Date: Thu, 21 Apr 2016 23:06:48 +0000 (-0400) Subject: cgroup, cpuset: replace cpuset_post_attach_flush() with cgroup_subsys->post_attach... X-Git-Tag: v4.6-rc6~18^2~1 X-Git-Url: http://git.cascardo.eti.br/?a=commitdiff_plain;h=5cf1cacb49aee39c3e02ae87068fc3c6430659b0;p=cascardo%2Flinux.git cgroup, cpuset: replace cpuset_post_attach_flush() with cgroup_subsys->post_attach callback Since e93ad19d0564 ("cpuset: make mm migration asynchronous"), cpuset kicks off asynchronous NUMA node migration if necessary during task migration and flushes it from cpuset_post_attach_flush() which is called at the end of __cgroup_procs_write(). This is to avoid performing migration with cgroup_threadgroup_rwsem write-locked which can lead to deadlock through dependency on kworker creation. memcg has a similar issue with charge moving, so let's convert it to an official callback rather than the current one-off cpuset specific function. This patch adds cgroup_subsys->post_attach callback and makes cpuset register cpuset_post_attach_flush() as its ->post_attach. The conversion is mostly one-to-one except that the new callback is called under cgroup_mutex. This is to guarantee that no other migration operations are started before ->post_attach callbacks are finished. cgroup_mutex is one of the outermost mutex in the system and has never been and shouldn't be a problem. We can add specialized synchronization around __cgroup_procs_write() but I don't think there's any noticeable benefit. Signed-off-by: Tejun Heo Cc: Li Zefan Cc: Johannes Weiner Cc: Michal Hocko Cc: # 4.4+ prerequisite for the next patch --- diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 3e39ae5bc799..5b17de62c962 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -444,6 +444,7 @@ struct cgroup_subsys { int (*can_attach)(struct cgroup_taskset *tset); void (*cancel_attach)(struct cgroup_taskset *tset); void (*attach)(struct cgroup_taskset *tset); + void (*post_attach)(void); int (*can_fork)(struct task_struct *task); void (*cancel_fork)(struct task_struct *task); void (*fork)(struct task_struct *task); diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index fea160ee5803..85a868ccb493 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -137,8 +137,6 @@ static inline void set_mems_allowed(nodemask_t nodemask) task_unlock(current); } -extern void cpuset_post_attach_flush(void); - #else /* !CONFIG_CPUSETS */ static inline bool cpusets_enabled(void) { return false; } @@ -245,10 +243,6 @@ static inline bool read_mems_allowed_retry(unsigned int seq) return false; } -static inline void cpuset_post_attach_flush(void) -{ -} - #endif /* !CONFIG_CPUSETS */ #endif /* _LINUX_CPUSET_H */ diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 671dc05c0b0f..909a7d31ffd3 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2825,9 +2825,10 @@ static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off, bool threadgroup) { struct task_struct *tsk; + struct cgroup_subsys *ss; struct cgroup *cgrp; pid_t pid; - int ret; + int ssid, ret; if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0) return -EINVAL; @@ -2875,8 +2876,10 @@ out_unlock_rcu: rcu_read_unlock(); out_unlock_threadgroup: percpu_up_write(&cgroup_threadgroup_rwsem); + for_each_subsys(ss, ssid) + if (ss->post_attach) + ss->post_attach(); cgroup_kn_unlock(of->kn); - cpuset_post_attach_flush(); return ret ?: nbytes; } diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 00ab5c2b7c5b..1902956baba1 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -58,7 +58,6 @@ #include #include #include -#include #include #include @@ -1016,7 +1015,7 @@ static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from, } } -void cpuset_post_attach_flush(void) +static void cpuset_post_attach(void) { flush_workqueue(cpuset_migrate_mm_wq); } @@ -2087,6 +2086,7 @@ struct cgroup_subsys cpuset_cgrp_subsys = { .can_attach = cpuset_can_attach, .cancel_attach = cpuset_cancel_attach, .attach = cpuset_attach, + .post_attach = cpuset_post_attach, .bind = cpuset_bind, .legacy_cftypes = files, .early_init = true,