sched: group scheduling, minor fixes
Minor bug fixes for the group scheduler:
- Use a mutex to serialize add/remove of task groups and also when
changing shares of a task group. Use the same mutex when printing
cfs_rq debugging stats for various task groups.
- Use list_for_each_entry_rcu in for_each_leaf_cfs_rq macro (when
walking task group list)
Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched.c b/kernel/sched.c
index 7f827b7..cfa6958 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -169,8 +169,6 @@
/* runqueue "owned" by this group on each cpu */
struct cfs_rq **cfs_rq;
unsigned long shares;
- /* spinlock to serialize modification to shares */
- spinlock_t lock;
struct rcu_head rcu;
};
@@ -182,6 +180,11 @@
static struct sched_entity *init_sched_entity_p[NR_CPUS];
static struct cfs_rq *init_cfs_rq_p[NR_CPUS];
+/* task_group_mutex serializes add/remove of task groups and also changes to
+ * a task group's cpu shares.
+ */
+static DEFINE_MUTEX(task_group_mutex);
+
/* Default task group.
* Every task in system belong to this group at bootup.
*/
@@ -221,9 +224,21 @@
p->se.parent = task_group(p)->se[cpu];
}
+static inline void lock_task_group_list(void)
+{
+ mutex_lock(&task_group_mutex);
+}
+
+static inline void unlock_task_group_list(void)
+{
+ mutex_unlock(&task_group_mutex);
+}
+
#else
static inline void set_task_cfs_rq(struct task_struct *p, unsigned int cpu) { }
+static inline void lock_task_group_list(void) { }
+static inline void unlock_task_group_list(void) { }
#endif /* CONFIG_FAIR_GROUP_SCHED */
@@ -6768,7 +6783,6 @@
se->parent = NULL;
}
init_task_group.shares = init_task_group_load;
- spin_lock_init(&init_task_group.lock);
#endif
for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
@@ -7008,14 +7022,15 @@
se->parent = NULL;
}
+ tg->shares = NICE_0_LOAD;
+
+ lock_task_group_list();
for_each_possible_cpu(i) {
rq = cpu_rq(i);
cfs_rq = tg->cfs_rq[i];
list_add_rcu(&cfs_rq->leaf_cfs_rq_list, &rq->leaf_cfs_rq_list);
}
-
- tg->shares = NICE_0_LOAD;
- spin_lock_init(&tg->lock);
+ unlock_task_group_list();
return tg;
@@ -7061,10 +7076,12 @@
struct cfs_rq *cfs_rq = NULL;
int i;
+ lock_task_group_list();
for_each_possible_cpu(i) {
cfs_rq = tg->cfs_rq[i];
list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
}
+ unlock_task_group_list();
BUG_ON(!cfs_rq);
@@ -7146,7 +7163,7 @@
if (shares < 2)
shares = 2;
- spin_lock(&tg->lock);
+ lock_task_group_list();
if (tg->shares == shares)
goto done;
@@ -7155,7 +7172,7 @@
set_se_shares(tg->se[i], shares);
done:
- spin_unlock(&tg->lock);
+ unlock_task_group_list();
return 0;
}
