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| author | Tejun Heo <tj@kernel.org> | 2015-09-11 21:00:19 +0200 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2015-09-22 18:46:53 +0200 |
| commit | 4530eddb59494b89650d6bcd980fc7f7717ad80c (patch) | |
| tree | 0f6212afa2e7e0e4724c5f12644508f1a0baf138 /kernel | |
| parent | cpuset: migrate memory only for threadgroup leaders (diff) | |
| download | linux-4530eddb59494b89650d6bcd980fc7f7717ad80c.tar.xz linux-4530eddb59494b89650d6bcd980fc7f7717ad80c.zip | |
cgroup, memcg, cpuset: implement cgroup_taskset_for_each_leader()
It wasn't explicitly documented but, when a process is being migrated,
cpuset and memcg depend on cgroup_taskset_first() returning the
threadgroup leader; however, this approach is somewhat ghetto and
would no longer work for the planned multi-process migration.
This patch introduces explicit cgroup_taskset_for_each_leader() which
iterates over only the threadgroup leaders and replaces
cgroup_taskset_first() usages for accessing the leader with it.
This prepares both memcg and cpuset for multi-process migration. This
patch also updates the documentation for cgroup_taskset_for_each() to
clarify the iteration rules and removes comments mentioning task
ordering in tasksets.
v2: A previous patch which added threadgroup leader test was dropped.
Patch updated accordingly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cgroup.c | 11 | ||||
| -rw-r--r-- | kernel/cpuset.c | 9 |
2 files changed, 4 insertions, 16 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 0be276ffe08a..7f4b85af03dc 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2217,13 +2217,6 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp, get_css_set(new_cset); rcu_assign_pointer(tsk->cgroups, new_cset); - - /* - * Use move_tail so that cgroup_taskset_first() still returns the - * leader after migration. This works because cgroup_migrate() - * ensures that the dst_cset of the leader is the first on the - * tset's dst_csets list. - */ list_move_tail(&tsk->cg_list, &new_cset->mg_tasks); /* @@ -2419,10 +2412,6 @@ static int cgroup_migrate(struct cgroup *cgrp, struct task_struct *leader, if (!cset->mg_src_cgrp) goto next; - /* - * cgroup_taskset_first() must always return the leader. - * Take care to avoid disturbing the ordering. - */ list_move_tail(&task->cg_list, &cset->mg_tasks); if (list_empty(&cset->mg_node)) list_add_tail(&cset->mg_node, &tset.src_csets); diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 0b361a0b58f6..e4d999929903 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -1488,7 +1488,7 @@ static void cpuset_attach(struct cgroup_subsys_state *css, /* static buf protected by cpuset_mutex */ static nodemask_t cpuset_attach_nodemask_to; struct task_struct *task; - struct task_struct *leader = cgroup_taskset_first(tset); + struct task_struct *leader; struct cpuset *cs = css_cs(css); struct cpuset *oldcs = cpuset_attach_old_cs; @@ -1514,12 +1514,11 @@ static void cpuset_attach(struct cgroup_subsys_state *css, } /* - * Change mm, possibly for multiple threads in a threadgroup. This - * is expensive and may sleep and should be moved outside migration - * path proper. + * Change mm for all threadgroup leaders. This is expensive and may + * sleep and should be moved outside migration path proper. */ cpuset_attach_nodemask_to = cs->effective_mems; - if (thread_group_leader(leader)) { + cgroup_taskset_for_each_leader(leader, tset) { struct mm_struct *mm = get_task_mm(leader); if (mm) { |