Mailing List Archive

The limitation that update_parent_subparts_cpumask() can only use
addmask & delmask in the given tmp cpumasks is fragile and may lead to
unexpected error. Add a new statically allocated cs_tmp_cpus cpumask
(protected by cpuset_mutex) for internal use so that all the three
temporary cpumasks can be freely used.

With this change, we can move the update_tasks_cpumask() for the
parent and update_sibling_cpumasks() for the sibling to inside
update_parent_subparts_cpumask().

Also add a init_tmpmasks() helper to handle initialization of the tmpmasks
structure when cpumasks are too big to be statically allocated on stack.

Signed-off-by: Waiman Long <longman@redhat.com>
---
kernel/cgroup/cpuset.c | 66 ++++++++++++++++++++++++------------------
1 file changed, 38 insertions(+), 28 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 12a0b583aca4..8604c919e1e4 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -208,6 +208,8 @@ struct cpuset {
struct cgroup_file partition_file;
};

+static cpumask_var_t cs_tmp_cpus; /* Temp cpumask for partition */
+
/*
* Partition root states:
*
@@ -668,6 +670,24 @@ static inline void free_cpumasks(struct cpuset *cs, struct tmpmasks *tmp)
}
}

+/*
+ * init_tmpmasks - Initialize the cpumasks in tmpmasks with the given ones
+ */
+#ifdef CONFIG_CPUMASK_OFFSTACK
+static inline void
+init_tmpmasks(struct tmpmasks *tmp, struct cpumask *new_cpus,
+ struct cpumask *addmask, struct cpumask *delmask)
+{
+ tmp->new_cpus = new_cpus;
+ tmp->addmask = addmask;
+ tmp->delmask = delmask;
+}
+#else
+static inline void
+init_tmpmasks(struct tmpmasks *tmp, struct cpumask *new_cpus,
+ struct cpumask *addmask, struct cpumask *delmask) { }
+#endif
+
/**
* alloc_trial_cpuset - allocate a trial cpuset
* @cs: the cpuset that the trial cpuset duplicates
@@ -1300,6 +1320,8 @@ enum subparts_cmd {

static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
int turning_on);
+static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
+ struct tmpmasks *tmp);

/*
* Update partition exclusive flag
@@ -1463,7 +1485,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
adding = cpumask_andnot(tmp->addmask, tmp->addmask,
parent->subparts_cpus);
/*
- * Empty cpumask is not allewed
+ * Empty cpumask is not allowed
*/
if (cpumask_empty(newmask)) {
part_error = PERR_CPUSEMPTY;
@@ -1583,8 +1605,11 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,

spin_unlock_irq(&callback_lock);

- if (adding || deleting)
+ if (adding || deleting) {
update_tasks_cpumask(parent, tmp->addmask);
+ if (parent->child_ecpus_count)
+ update_sibling_cpumasks(parent, cs, tmp);
+ }

/*
* For partcmd_update without newmask, it is being called from
@@ -1839,18 +1864,13 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
return 0;

-#ifdef CONFIG_CPUMASK_OFFSTACK
/*
* Use the cpumasks in trialcs for tmpmasks when they are pointers
- * to allocated cpumasks.
- *
- * Note that update_parent_subparts_cpumask() uses only addmask &
- * delmask, but not new_cpus.
+ * to allocated cpumasks & save the newmask into cs_tmp_cpus.
*/
- tmp.addmask = trialcs->subparts_cpus;
- tmp.delmask = trialcs->effective_cpus;
- tmp.new_cpus = NULL;
-#endif
+ cpumask_copy(cs_tmp_cpus, trialcs->cpus_allowed);
+ init_tmpmasks(&tmp, trialcs->cpus_allowed, trialcs->subparts_cpus,
+ trialcs->effective_cpus);

retval = validate_change(cs, trialcs);

@@ -1870,7 +1890,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
parent = parent_cs(cs);
cpuset_for_each_child(cp, css, parent)
if (is_partition_valid(cp) &&
- cpumask_intersects(trialcs->cpus_allowed, cp->cpus_allowed)) {
+ cpumask_intersects(cs_tmp_cpus, cp->cpus_allowed)) {
rcu_read_unlock();
update_parent_subparts_cpumask(cp, partcmd_invalidate, NULL, &tmp);
rcu_read_lock();
@@ -1887,13 +1907,15 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
NULL, &tmp);
else
update_parent_subparts_cpumask(cs, partcmd_update,
- trialcs->cpus_allowed, &tmp);
+ cs_tmp_cpus, &tmp);
}

+ /* Restore trialcs->cpus_allowed */
+ cpumask_copy(trialcs->cpus_allowed, cs_tmp_cpus);
compute_effective_cpumask(trialcs->effective_cpus, trialcs,
parent_cs(cs));
spin_lock_irq(&callback_lock);
- cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
+ cpumask_copy(cs->cpus_allowed, cs_tmp_cpus);

/*
* Make sure that subparts_cpus, if not empty, is a subset of
@@ -1914,11 +1936,6 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
}
spin_unlock_irq(&callback_lock);

-#ifdef CONFIG_CPUMASK_OFFSTACK
- /* Now trialcs->cpus_allowed is available */
- tmp.new_cpus = trialcs->cpus_allowed;
-#endif
-
/* effective_cpus will be updated here */
update_cpumasks_hier(cs, &tmp, false);

@@ -2343,13 +2360,11 @@ static int update_prstate(struct cpuset *cs, int new_prs)

err = update_parent_subparts_cpumask(cs, partcmd_enable,
NULL, &tmpmask);
- if (err)
- goto out;
} else if (old_prs && new_prs) {
/*
* A change in load balance state only, no change in cpumasks.
*/
- goto out;
+ ;
} else {
/*
* Switching back to member is always allowed even if it
@@ -2369,12 +2384,6 @@ static int update_prstate(struct cpuset *cs, int new_prs)
spin_unlock_irq(&callback_lock);
}
}
-
- update_tasks_cpumask(parent, tmpmask.new_cpus);
-
- if (parent->child_ecpus_count)
- update_sibling_cpumasks(parent, cs, &tmpmask);
-
out:
/*
* Make partition invalid & disable CS_CPU_EXCLUSIVE if an error
@@ -3500,6 +3509,7 @@ int __init cpuset_init(void)
BUG_ON(!alloc_cpumask_var(&top_cpuset.cpus_allowed, GFP_KERNEL));
BUG_ON(!alloc_cpumask_var(&top_cpuset.effective_cpus, GFP_KERNEL));
BUG_ON(!zalloc_cpumask_var(&top_cpuset.subparts_cpus, GFP_KERNEL));
+ BUG_ON(!zalloc_cpumask_var(&cs_tmp_cpus, GFP_KERNEL));

cpumask_setall(top_cpuset.cpus_allowed);
nodes_setall(top_cpuset.mems_allowed);
--
2.31.1