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cgroup, cpuset: replace cpuset_post_attach_flush() with cgroup_subsys->post_attach callback

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Since e93ad19d05 ("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
This commit is contained in:
Tejun Heo 2016-04-21 19:06:48 -04:00
parent bcc981e9ed
commit 5cf1cacb49
4 changed files with 8 additions and 10 deletions
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6
include/linux/cpuset.h
View file

@ -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 */