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authorTejun Heo <tj@kernel.org>2013-01-07 08:51:07 -0800
committerTejun Heo <tj@kernel.org>2013-01-07 08:51:07 -0800
commit452477fa68c6d8ef80adebd05194c1c157ad9a53 (patch)
tree28682f4307a4e4bc2180d18ccb71a262700699df /kernel/cpuset.c
parent8d03394877ecdf87e1d694664c460747b8e05aa1 (diff)
downloadlinux-452477fa68c6d8ef80adebd05194c1c157ad9a53.tar.bz2
cpuset: pin down cpus and mems while a task is being attached
cpuset is scheduled to be decoupled from cgroup_lock which will make configuration updates race with task migration. Any config update will be allowed to happen between ->can_attach() and ->attach(). If such config update removes either all cpus or mems, by the time ->attach() is called, the condition verified by ->can_attach(), that the cpuset is capable of hosting the tasks, is no longer true. This patch adds cpuset->attach_in_progress which is incremented from ->can_attach() and decremented when the attach operation finishes either successfully or not. validate_change() treats cpusets w/ non-zero ->attach_in_progress like cpusets w/ tasks and refuses to remove all cpus or mems from it. This currently doesn't make any functional difference as everything is protected by cgroup_mutex but enables decoupling the locking. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Diffstat (limited to 'kernel/cpuset.c')
-rw-r--r--kernel/cpuset.c28
1 files changed, 26 insertions, 2 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index a7bb547786d7..4334576f5d6a 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -91,6 +91,12 @@ struct cpuset {
struct fmeter fmeter; /* memory_pressure filter */
+ /*
+ * Tasks are being attached to this cpuset. Used to prevent
+ * zeroing cpus/mems_allowed between ->can_attach() and ->attach().
+ */
+ int attach_in_progress;
+
/* partition number for rebuild_sched_domains() */
int pn;
@@ -468,9 +474,12 @@ static int validate_change(const struct cpuset *cur, const struct cpuset *trial)
goto out;
}
- /* Cpusets with tasks can't have empty cpus_allowed or mems_allowed */
+ /*
+ * Cpusets with tasks - existing or newly being attached - can't
+ * have empty cpus_allowed or mems_allowed.
+ */
ret = -ENOSPC;
- if (cgroup_task_count(cur->css.cgroup) &&
+ if ((cgroup_task_count(cur->css.cgroup) || cur->attach_in_progress) &&
(cpumask_empty(trial->cpus_allowed) ||
nodes_empty(trial->mems_allowed)))
goto out;
@@ -1386,9 +1395,21 @@ static int cpuset_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
return ret;
}
+ /*
+ * Mark attach is in progress. This makes validate_change() fail
+ * changes which zero cpus/mems_allowed.
+ */
+ cs->attach_in_progress++;
+
return 0;
}
+static void cpuset_cancel_attach(struct cgroup *cgrp,
+ struct cgroup_taskset *tset)
+{
+ cgroup_cs(cgrp)->attach_in_progress--;
+}
+
/*
* Protected by cgroup_mutex. cpus_attach is used only by cpuset_attach()
* but we can't allocate it dynamically there. Define it global and
@@ -1441,6 +1462,8 @@ static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
&cpuset_attach_nodemask_to);
mmput(mm);
}
+
+ cs->attach_in_progress--;
}
/* The various types of files and directories in a cpuset file system */
@@ -1908,6 +1931,7 @@ struct cgroup_subsys cpuset_subsys = {
.css_offline = cpuset_css_offline,
.css_free = cpuset_css_free,
.can_attach = cpuset_can_attach,
+ .cancel_attach = cpuset_cancel_attach,
.attach = cpuset_attach,
.subsys_id = cpuset_subsys_id,
.base_cftypes = files,