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cgroup/cpuset: Fix violation of cpuset locking rule
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[ Upstream commit 6ba34d3 ]

The cpuset fields that manage partition root state do not strictly
follow the cpuset locking rule that update to cpuset has to be done
with both the callback_lock and cpuset_mutex held. This is now fixed
by making sure that the locking rule is upheld.

Fixes: 3881b86 ("cpuset: Add an error state to cpuset.sched.partition")
Fixes: 4b842da ("cpuset: Make CPU hotplug work with partition")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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@gregkh
Waiman Long authored and gregkh committed Sep 15, 2021
1 parent cbc9766 commit 10dfcfd
Showing 1 changed file with 35 additions and 23 deletions.
58 changes: 35 additions & 23 deletions kernel/cgroup/cpuset.c
View file
Expand Up @@ -1148,6 +1148,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
struct cpuset *parent = parent_cs(cpuset);
int adding; /* Moving cpus from effective_cpus to subparts_cpus */
int deleting; /* Moving cpus from subparts_cpus to effective_cpus */
int new_prs;
bool part_error = false; /* Partition error? */

percpu_rwsem_assert_held(&cpuset_rwsem);
Expand Down Expand Up @@ -1183,6 +1184,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
* A cpumask update cannot make parent's effective_cpus become empty.
*/
adding = deleting = false;
new_prs = cpuset->partition_root_state;
if (cmd == partcmd_enable) {
cpumask_copy(tmp->addmask, cpuset->cpus_allowed);
adding = true;
Expand Down Expand Up @@ -1247,11 +1249,11 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
switch (cpuset->partition_root_state) {
case PRS_ENABLED:
if (part_error)
cpuset->partition_root_state = PRS_ERROR;
new_prs = PRS_ERROR;
break;
case PRS_ERROR:
if (!part_error)
cpuset->partition_root_state = PRS_ENABLED;
new_prs = PRS_ENABLED;
break;
}
/*
Expand All @@ -1260,10 +1262,10 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
part_error = (prev_prs == PRS_ERROR);
}

if (!part_error && (cpuset->partition_root_state == PRS_ERROR))
if (!part_error && (new_prs == PRS_ERROR))
return 0; /* Nothing need to be done */

if (cpuset->partition_root_state == PRS_ERROR) {
if (new_prs == PRS_ERROR) {
/*
* Remove all its cpus from parent's subparts_cpus.
*/
Expand All @@ -1272,7 +1274,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
parent->subparts_cpus);
}

if (!adding && !deleting)
if (!adding && !deleting && (new_prs == cpuset->partition_root_state))
return 0;

/*
Expand All @@ -1299,6 +1301,9 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
}

parent->nr_subparts_cpus = cpumask_weight(parent->subparts_cpus);

if (cpuset->partition_root_state != new_prs)
cpuset->partition_root_state = new_prs;
spin_unlock_irq(&callback_lock);

return cmd == partcmd_update;
Expand All @@ -1321,6 +1326,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
struct cpuset *cp;
struct cgroup_subsys_state *pos_css;
bool need_rebuild_sched_domains = false;
int new_prs;

rcu_read_lock();
cpuset_for_each_descendant_pre(cp, pos_css, cs) {
Expand Down Expand Up @@ -1360,7 +1366,8 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
* update_tasks_cpumask() again for tasks in the parent
* cpuset if the parent's subparts_cpus changes.
*/
if ((cp != cs) && cp->partition_root_state) {
new_prs = cp->partition_root_state;
if ((cp != cs) && new_prs) {
switch (parent->partition_root_state) {
case PRS_DISABLED:
/*
Expand All @@ -1370,7 +1377,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
*/
WARN_ON_ONCE(cp->partition_root_state
!= PRS_ERROR);
cp->partition_root_state = PRS_DISABLED;
new_prs = PRS_DISABLED;

/*
* clear_bit() is an atomic operation and
Expand All @@ -1391,11 +1398,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
/*
* When parent is invalid, it has to be too.
*/
cp->partition_root_state = PRS_ERROR;
if (cp->nr_subparts_cpus) {
cp->nr_subparts_cpus = 0;
cpumask_clear(cp->subparts_cpus);
}
new_prs = PRS_ERROR;
break;
}
}
Expand All @@ -1407,8 +1410,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
spin_lock_irq(&callback_lock);

cpumask_copy(cp->effective_cpus, tmp->new_cpus);
if (cp->nr_subparts_cpus &&
(cp->partition_root_state != PRS_ENABLED)) {
if (cp->nr_subparts_cpus && (new_prs != PRS_ENABLED)) {
cp->nr_subparts_cpus = 0;
cpumask_clear(cp->subparts_cpus);
} else if (cp->nr_subparts_cpus) {
Expand All @@ -1435,6 +1437,10 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
= cpumask_weight(cp->subparts_cpus);
}
}

if (new_prs != cp->partition_root_state)
cp->partition_root_state = new_prs;

spin_unlock_irq(&callback_lock);

WARN_ON(!is_in_v2_mode() &&
Expand Down Expand Up @@ -1944,25 +1950,25 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
*/
static int update_prstate(struct cpuset *cs, int new_prs)
{
int err;
int err, old_prs = cs->partition_root_state;
struct cpuset *parent = parent_cs(cs);
struct tmpmasks tmpmask;

if (new_prs == cs->partition_root_state)
if (old_prs == new_prs)
return 0;

/*
* Cannot force a partial or invalid partition root to a full
* partition root.
*/
if (new_prs && (cs->partition_root_state < 0))
if (new_prs && (old_prs == PRS_ERROR))
return -EINVAL;

if (alloc_cpumasks(NULL, &tmpmask))
return -ENOMEM;

err = -EINVAL;
if (!cs->partition_root_state) {
if (!old_prs) {
/*
* Turning on partition root requires setting the
* CS_CPU_EXCLUSIVE bit implicitly as well and cpus_allowed
Expand All @@ -1981,14 +1987,12 @@ static int update_prstate(struct cpuset *cs, int new_prs)
update_flag(CS_CPU_EXCLUSIVE, cs, 0);
goto out;
}
cs->partition_root_state = PRS_ENABLED;
} else {
/*
* Turning off partition root will clear the
* CS_CPU_EXCLUSIVE bit.
*/
if (cs->partition_root_state == PRS_ERROR) {
cs->partition_root_state = PRS_DISABLED;
if (old_prs == PRS_ERROR) {
update_flag(CS_CPU_EXCLUSIVE, cs, 0);
err = 0;
goto out;
Expand All @@ -1999,8 +2003,6 @@ static int update_prstate(struct cpuset *cs, int new_prs)
if (err)
goto out;

cs->partition_root_state = PRS_DISABLED;

/* Turning off CS_CPU_EXCLUSIVE will not return error */
update_flag(CS_CPU_EXCLUSIVE, cs, 0);
}
Expand All @@ -2017,6 +2019,12 @@ static int update_prstate(struct cpuset *cs, int new_prs)

rebuild_sched_domains_locked();
out:
if (!err) {
spin_lock_irq(&callback_lock);
cs->partition_root_state = new_prs;
spin_unlock_irq(&callback_lock);
}

free_cpumasks(NULL, &tmpmask);
return err;
}
Expand Down Expand Up @@ -3080,8 +3088,10 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
if (is_partition_root(cs) && (cpumask_empty(&new_cpus) ||
(parent->partition_root_state == PRS_ERROR))) {
if (cs->nr_subparts_cpus) {
spin_lock_irq(&callback_lock);
cs->nr_subparts_cpus = 0;
cpumask_clear(cs->subparts_cpus);
spin_unlock_irq(&callback_lock);
compute_effective_cpumask(&new_cpus, cs, parent);
}

Expand All @@ -3095,7 +3105,9 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
cpumask_empty(&new_cpus)) {
update_parent_subparts_cpumask(cs, partcmd_disable,
NULL, tmp);
spin_lock_irq(&callback_lock);
cs->partition_root_state = PRS_ERROR;
spin_unlock_irq(&callback_lock);
}
cpuset_force_rebuild();
}
Expand Down

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