[PATCH 08/10] cpuset: introduce effective_{cpumask|nodemask}_cpuset()
From: Li Zefan
Date: Fri Apr 19 2013 - 08:28:55 EST
effective_cpumask_cpuset() returns an ancestor cpuset which has
non-empty cpumask.
If a cpuset is empty and the tasks in it need to update their
cpus_allowed, they take on the ancestor cpuset's cpumask.
This currently won't change any behavior, but it will later allow us
to keep tasks in empty cpusets.
Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
---
kernel/cpuset.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 65 insertions(+), 11 deletions(-)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index c4f9ebd..741e652 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -794,6 +794,45 @@ void rebuild_sched_domains(void)
mutex_unlock(&cpuset_mutex);
}
+/*
+ * effective_cpumask_cpuset - return nearest ancestor with non-empty cpus
+ * @cs: the cpuset in interest
+ *
+ * A cpuset's effective cpumask is the cpumask of the nearest ancestor
+ * with non-empty cpus. We use effective cpumask whenever:
+ * - we update tasks' cpus_allowed. (they take on the ancestor's cpumask
+ * if the cpuset they reside in has no cpus)
+ * - we want to retrieve task_cs(tsk)'s cpus_allowed.
+ *
+ * Called with cpuset_mutex held. cpuset_cpus_allowed_fallback() is an
+ * exception. See comments there.
+ */
+static struct cpuset *effective_cpumask_cpuset(struct cpuset *cs)
+{
+ while (cpumask_empty(cs->cpus_allowed))
+ cs = parent_cs(cs);
+ return cs;
+}
+
+/*
+ * effective_nodemask_cpuset - return nearest ancestor with non-empty mems
+ * @cs: the cpuset in interest
+ *
+ * A cpuset's effective nodemask is the nodemask of the nearest ancestor
+ * with non-empty memss. We use effective nodemask whenever:
+ * - we update tasks' mems_allowed. (they take on the ancestor's nodemask
+ * if the cpuset they reside in has no mems)
+ * - we want to retrieve task_cs(tsk)'s mems_allowed.
+ *
+ * Called with cpuset_mutex held.
+ */
+static struct cpuset *effective_nodemask_cpuset(struct cpuset *cs)
+{
+ while (nodes_empty(cs->mems_allowed))
+ cs = parent_cs(cs);
+ return cs;
+}
+
/**
* cpuset_change_cpumask - make a task's cpus_allowed the same as its cpuset's
* @tsk: task to test
@@ -808,7 +847,10 @@ void rebuild_sched_domains(void)
static void cpuset_change_cpumask(struct task_struct *tsk,
struct cgroup_scanner *scan)
{
- set_cpus_allowed_ptr(tsk, ((cgroup_cs(scan->cg))->cpus_allowed));
+ struct cpuset *cpus_cs;
+
+ cpus_cs = effective_cpumask_cpuset(cgroup_cs(scan->cg));
+ set_cpus_allowed_ptr(tsk, cpus_cs->cpus_allowed);
}
/**
@@ -923,12 +965,14 @@ static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
const nodemask_t *to)
{
struct task_struct *tsk = current;
+ struct cpuset *mems_cs;
tsk->mems_allowed = *to;
do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL);
- guarantee_online_mems(task_cs(tsk),&tsk->mems_allowed);
+ mems_cs = effective_nodemask_cpuset(task_cs(tsk));
+ guarantee_online_mems(mems_cs, &tsk->mems_allowed);
}
/*
@@ -1021,10 +1065,11 @@ static void update_tasks_nodemask(struct cpuset *cs, struct ptr_heap *heap)
{
static nodemask_t newmems; /* protected by cpuset_mutex */
struct cgroup_scanner scan;
+ struct cpuset *mems_cs = effective_nodemask_cpuset(cs);
cpuset_being_rebound = cs; /* causes mpol_dup() rebind */
- guarantee_online_mems(cs, &newmems);
+ guarantee_online_mems(mems_cs, &newmems);
scan.cg = cs->css.cgroup;
scan.test_task = NULL;
@@ -1408,6 +1453,8 @@ static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
struct cgroup *oldcgrp = cgroup_taskset_cur_cgroup(tset);
struct cpuset *cs = cgroup_cs(cgrp);
struct cpuset *oldcs = cgroup_cs(oldcgrp);
+ struct cpuset *cpus_cs = effective_cpumask_cpuset(cs);
+ struct cpuset *mems_cs = effective_nodemask_cpuset(cs);
mutex_lock(&cpuset_mutex);
@@ -1415,9 +1462,9 @@ static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
if (cs == &top_cpuset)
cpumask_copy(cpus_attach, cpu_possible_mask);
else
- guarantee_online_cpus(cs, cpus_attach);
+ guarantee_online_cpus(cpus_cs, cpus_attach);
- guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
+ guarantee_online_mems(mems_cs, &cpuset_attach_nodemask_to);
cgroup_taskset_for_each(task, cgrp, tset) {
/*
@@ -1436,9 +1483,11 @@ static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
*/
mm = get_task_mm(leader);
if (mm) {
+ struct cpuset *mems_oldcs = effective_nodemask_cpuset(oldcs);
+
mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
if (is_memory_migrate(cs))
- cpuset_migrate_mm(mm, &oldcs->mems_allowed,
+ cpuset_migrate_mm(mm, &mems_oldcs->mems_allowed,
&cpuset_attach_nodemask_to);
mmput(mm);
}
@@ -2227,20 +2276,23 @@ void __init cpuset_init_smp(void)
void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
{
+ struct cpuset *cpus_cs;
+
mutex_lock(&callback_mutex);
task_lock(tsk);
- guarantee_online_cpus(task_cs(tsk), pmask);
+ cpus_cs = effective_cpumask_cpuset(task_cs(tsk));
+ guarantee_online_cpus(cpus_cs, pmask);
task_unlock(tsk);
mutex_unlock(&callback_mutex);
}
void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
{
- const struct cpuset *cs;
+ const struct cpuset *cpus_cs;
rcu_read_lock();
- cs = task_cs(tsk);
- do_set_cpus_allowed(tsk, cs->cpus_allowed);
+ cpus_cs = effective_cpumask_cpuset(task_cs(tsk));
+ do_set_cpus_allowed(tsk, cpus_cs->cpus_allowed);
rcu_read_unlock();
/*
@@ -2279,11 +2331,13 @@ void cpuset_init_current_mems_allowed(void)
nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
{
+ struct cpuset *mems_cs;
nodemask_t mask;
mutex_lock(&callback_mutex);
task_lock(tsk);
- guarantee_online_mems(task_cs(tsk), &mask);
+ mems_cs = effective_nodemask_cpuset(task_cs(tsk));
+ guarantee_online_mems(mems_cs, &mask);
task_unlock(tsk);
mutex_unlock(&callback_mutex);
--
1.8.0.2
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