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Message-ID: <20251104013037.296013-4-longman@redhat.com>
Date: Mon, 3 Nov 2025 20:30:37 -0500
From: Waiman Long <longman@...hat.com>
To: Tejun Heo <tj@...nel.org>,
Johannes Weiner <hannes@...xchg.org>,
Michal Koutný <mkoutny@...e.com>
Cc: cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org,
Chen Ridong <chenridong@...wei.com>,
Gabriele Monaco <gmonaco@...hat.com>,
Frederic Weisbecker <frederic@...nel.org>,
Waiman Long <longman@...hat.com>
Subject: [cgroup/for-6.19 PATCH v2 3/3] cgroup/cpuset: Globally track isolated_cpus update
The current cpuset code passes a local isolcpus_updated flag around in a
number of functions to determine if external isolation related cpumasks
like wq_unbound_cpumask should be updated. It is a bit cumbersome and
makes the code more complex. Simplify the code by using a global boolean
flag "isolated_cpus_updating" to track this. This flag will be set in
isolated_cpus_update() and cleared in update_isolation_cpumasks().
No functional change is expected.
Signed-off-by: Waiman Long <longman@...hat.com>
---
kernel/cgroup/cpuset.c | 73 ++++++++++++++++++++----------------------
1 file changed, 35 insertions(+), 38 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 0c49905df394..854fe4cc1358 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -81,6 +81,13 @@ static cpumask_var_t subpartitions_cpus;
*/
static cpumask_var_t isolated_cpus;
+/*
+ * isolated_cpus updating flag (protected by cpuset_mutex)
+ * Set if isolated_cpus is going to be updated in the current
+ * cpuset_mutex crtical section.
+ */
+static bool isolated_cpus_updating;
+
/*
* Housekeeping (HK_TYPE_DOMAIN) CPUs at boot
*/
@@ -1327,6 +1334,8 @@ static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus
cpumask_or(isolated_cpus, isolated_cpus, xcpus);
else
cpumask_andnot(isolated_cpus, isolated_cpus, xcpus);
+
+ isolated_cpus_updating = true;
}
/*
@@ -1334,15 +1343,12 @@ static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus
* @new_prs: new partition_root_state
* @parent: parent cpuset
* @xcpus: exclusive CPUs to be added
- * Return: true if isolated_cpus modified, false otherwise
*
* Remote partition if parent == NULL
*/
-static bool partition_xcpus_add(int new_prs, struct cpuset *parent,
+static void partition_xcpus_add(int new_prs, struct cpuset *parent,
struct cpumask *xcpus)
{
- bool isolcpus_updated;
-
WARN_ON_ONCE(new_prs < 0);
lockdep_assert_held(&callback_lock);
if (!parent)
@@ -1352,13 +1358,11 @@ static bool partition_xcpus_add(int new_prs, struct cpuset *parent,
if (parent == &top_cpuset)
cpumask_or(subpartitions_cpus, subpartitions_cpus, xcpus);
- isolcpus_updated = (new_prs != parent->partition_root_state);
- if (isolcpus_updated)
+ if (new_prs != parent->partition_root_state)
isolated_cpus_update(parent->partition_root_state, new_prs,
xcpus);
cpumask_andnot(parent->effective_cpus, parent->effective_cpus, xcpus);
- return isolcpus_updated;
}
/*
@@ -1366,15 +1370,12 @@ static bool partition_xcpus_add(int new_prs, struct cpuset *parent,
* @old_prs: old partition_root_state
* @parent: parent cpuset
* @xcpus: exclusive CPUs to be removed
- * Return: true if isolated_cpus modified, false otherwise
*
* Remote partition if parent == NULL
*/
-static bool partition_xcpus_del(int old_prs, struct cpuset *parent,
+static void partition_xcpus_del(int old_prs, struct cpuset *parent,
struct cpumask *xcpus)
{
- bool isolcpus_updated;
-
WARN_ON_ONCE(old_prs < 0);
lockdep_assert_held(&callback_lock);
if (!parent)
@@ -1383,14 +1384,12 @@ static bool partition_xcpus_del(int old_prs, struct cpuset *parent,
if (parent == &top_cpuset)
cpumask_andnot(subpartitions_cpus, subpartitions_cpus, xcpus);
- isolcpus_updated = (old_prs != parent->partition_root_state);
- if (isolcpus_updated)
+ if (old_prs != parent->partition_root_state)
isolated_cpus_update(old_prs, parent->partition_root_state,
xcpus);
cpumask_and(xcpus, xcpus, cpu_active_mask);
cpumask_or(parent->effective_cpus, parent->effective_cpus, xcpus);
- return isolcpus_updated;
}
/*
@@ -1432,17 +1431,24 @@ static bool isolated_cpus_can_update(struct cpumask *add_cpus,
return res;
}
-static void update_isolation_cpumasks(bool isolcpus_updated)
+/*
+ * update_isolation_cpumasks - Update external isolation related CPU masks
+ *
+ * The following external CPU masks will be updated if necessary:
+ * - workqueue unbound cpumask
+ */
+static void update_isolation_cpumasks(void)
{
int ret;
- lockdep_assert_cpus_held();
-
- if (!isolcpus_updated)
+ if (!isolated_cpus_updating)
return;
+ lockdep_assert_cpus_held();
+
ret = workqueue_unbound_exclude_cpumask(isolated_cpus);
WARN_ON_ONCE(ret < 0);
+ isolated_cpus_updating = false;
}
/**
@@ -1567,8 +1573,6 @@ static inline bool is_local_partition(struct cpuset *cs)
static int remote_partition_enable(struct cpuset *cs, int new_prs,
struct tmpmasks *tmp)
{
- bool isolcpus_updated;
-
/*
* The user must have sysadmin privilege.
*/
@@ -1595,11 +1599,11 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
return PERR_HKEEPING;
spin_lock_irq(&callback_lock);
- isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
+ partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
list_add(&cs->remote_sibling, &remote_children);
cpumask_copy(cs->effective_xcpus, tmp->new_cpus);
spin_unlock_irq(&callback_lock);
- update_isolation_cpumasks(isolcpus_updated);
+ update_isolation_cpumasks();
cpuset_force_rebuild();
cs->prs_err = 0;
@@ -1622,15 +1626,12 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
*/
static void remote_partition_disable(struct cpuset *cs, struct tmpmasks *tmp)
{
- bool isolcpus_updated;
-
WARN_ON_ONCE(!is_remote_partition(cs));
WARN_ON_ONCE(!cpumask_subset(cs->effective_xcpus, subpartitions_cpus));
spin_lock_irq(&callback_lock);
list_del_init(&cs->remote_sibling);
- isolcpus_updated = partition_xcpus_del(cs->partition_root_state,
- NULL, cs->effective_xcpus);
+ partition_xcpus_del(cs->partition_root_state, NULL, cs->effective_xcpus);
if (cs->prs_err)
cs->partition_root_state = -cs->partition_root_state;
else
@@ -1640,7 +1641,7 @@ static void remote_partition_disable(struct cpuset *cs, struct tmpmasks *tmp)
compute_excpus(cs, cs->effective_xcpus);
reset_partition_data(cs);
spin_unlock_irq(&callback_lock);
- update_isolation_cpumasks(isolcpus_updated);
+ update_isolation_cpumasks();
cpuset_force_rebuild();
/*
@@ -1665,7 +1666,6 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
{
bool adding, deleting;
int prs = cs->partition_root_state;
- int isolcpus_updated = 0;
if (WARN_ON_ONCE(!is_remote_partition(cs)))
return;
@@ -1701,9 +1701,9 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
spin_lock_irq(&callback_lock);
if (adding)
- isolcpus_updated += partition_xcpus_add(prs, NULL, tmp->addmask);
+ partition_xcpus_add(prs, NULL, tmp->addmask);
if (deleting)
- isolcpus_updated += partition_xcpus_del(prs, NULL, tmp->delmask);
+ partition_xcpus_del(prs, NULL, tmp->delmask);
/*
* Need to update effective_xcpus and exclusive_cpus now as
* update_sibling_cpumasks() below may iterate back to the same cs.
@@ -1712,7 +1712,7 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
if (xcpus)
cpumask_copy(cs->exclusive_cpus, xcpus);
spin_unlock_irq(&callback_lock);
- update_isolation_cpumasks(isolcpus_updated);
+ update_isolation_cpumasks();
if (adding || deleting)
cpuset_force_rebuild();
@@ -1793,7 +1793,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
int deleting; /* Deleting cpus from parent's effective_cpus */
int old_prs, new_prs;
int part_error = PERR_NONE; /* Partition error? */
- int isolcpus_updated = 0;
struct cpumask *xcpus = user_xcpus(cs);
int parent_prs = parent->partition_root_state;
bool nocpu;
@@ -2072,14 +2071,12 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
* and vice versa.
*/
if (adding)
- isolcpus_updated += partition_xcpus_del(old_prs, parent,
- tmp->addmask);
+ partition_xcpus_del(old_prs, parent, tmp->addmask);
if (deleting)
- isolcpus_updated += partition_xcpus_add(new_prs, parent,
- tmp->delmask);
+ partition_xcpus_add(new_prs, parent, tmp->delmask);
spin_unlock_irq(&callback_lock);
- update_isolation_cpumasks(isolcpus_updated);
+ update_isolation_cpumasks();
if ((old_prs != new_prs) && (cmd == partcmd_update))
update_partition_exclusive_flag(cs, new_prs);
@@ -3102,7 +3099,7 @@ static int update_prstate(struct cpuset *cs, int new_prs)
else if (isolcpus_updated)
isolated_cpus_update(old_prs, new_prs, cs->effective_xcpus);
spin_unlock_irq(&callback_lock);
- update_isolation_cpumasks(isolcpus_updated);
+ update_isolation_cpumasks();
/* Force update if switching back to member & update effective_xcpus */
update_cpumasks_hier(cs, &tmpmask, !new_prs);
--
2.51.1
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