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authorTejun Heo <tj@kernel.org>2016-04-21 19:06:48 -0400
committerTejun Heo <tj@kernel.org>2016-04-25 15:45:14 -0400
commit5cf1cacb49aee39c3e02ae87068fc3c6430659b0 (patch)
tree569518d16093a55169e4ef1cd5399e9a3f620d06
parentbcc981e9ed84c678533299d7eff17d2c81e4d5de (diff)
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 <tj@kernel.org> Cc: Li Zefan <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: <stable@vger.kernel.org> # 4.4+ prerequisite for the next patch
-rw-r--r--include/linux/cgroup-defs.h1
-rw-r--r--include/linux/cpuset.h6
-rw-r--r--kernel/cgroup.c7
-rw-r--r--kernel/cpuset.c4
4 files changed, 8 insertions, 10 deletions
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 <asm/uaccess.h>
#include <linux/atomic.h>
#include <linux/mutex.h>
-#include <linux/workqueue.h>
#include <linux/cgroup.h>
#include <linux/wait.h>
@@ -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,