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Message-Id: <20250928071306.3797436-12-chenridong@huaweicloud.com>
Date: Sun, 28 Sep 2025 07:13:01 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: longman@...hat.com,
tj@...nel.org,
hannes@...xchg.org,
mkoutny@...e.com
Cc: cgups@...r.kernel.org,
linux-kernel@...r.kernel.org,
lujialin4@...wei.com,
chenridong@...wei.com
Subject: [PATCH -next RFC 11/16] cpuset: simplify partition update logic for hotplug tasks
From: Chen Ridong <chenridong@...wei.com>
Simplify the partition update logic in cpuset_hotplug_update_tasks() by
calling the unified local_partition_update() interface.
For local partitions, the previous patch introduced local_partition_update
which handles both validation state transitions:
- Invalidates local partitions that fail validation checks
- Transitions invalid partitions to valid state when no errors are detected
This eliminates the need for separate transition logic
in cpuset_hotplug_update_tasks(), which can now simply call
local_partition_update() to handle all local partition changes.
This patch simplifies the logic by always proceeding to update_tasks for
remote partitions, regardless of whether they were disabled or not. Since
the original code didn't perform any meaningful operations for non-disabled
remote partitions, this change should not affect functionality.
The partition_cmd mechanism can now be safely removed as it is no longer
referenced by any code paths after the partition update logic
simplification.
Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
kernel/cgroup/cpuset.c | 67 ++++++++++++++++--------------------------
1 file changed, 26 insertions(+), 41 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 9e98df542715..a1896a199c8b 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1211,17 +1211,6 @@ static void compute_effective_cpumask(struct cpumask *new_cpus,
cpumask_and(new_cpus, cs->cpus_allowed, parent->effective_cpus);
}
-/*
- * Commands for update_parent_effective_cpumask
- */
-enum partition_cmd {
- partcmd_enable, /* Enable partition root */
- partcmd_enablei, /* Enable isolated partition root */
- partcmd_disable, /* Disable partition root */
- partcmd_update, /* Update parent's effective_cpus */
- partcmd_invalidate, /* Make partition invalid */
-};
-
static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
struct tmpmasks *tmp);
@@ -2062,6 +2051,9 @@ static int __local_partition_update(struct cpuset *cs, struct cpumask *xcpus,
update_partition_sd_lb(cs, old_prs);
return part_error;
}
+ /* Nothing changes, return PERR_NONE */
+ if (new_prs == old_prs && cpumask_equal(excpus, cs->effective_xcpus))
+ return PERR_NONE;
cpumask_updated = cpumask_andnot(tmp->addmask, excpus, cs->effective_xcpus);
cpumask_updated |= cpumask_andnot(tmp->delmask, cs->effective_xcpus, excpus);
@@ -3868,8 +3860,6 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
static nodemask_t new_mems;
bool cpus_updated;
bool mems_updated;
- bool remote;
- int partcmd = -1;
struct cpuset *parent;
retry:
wait_event(cpuset_attach_wq, cs->attach_in_progress == 0);
@@ -3896,16 +3886,15 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
* Compute effective_cpus for valid partition root, may invalidate
* child partition roots if necessary.
*/
- remote = is_remote_partition(cs);
- if (remote || (is_partition_valid(cs) && is_partition_valid(parent)))
+ if (is_remote_partition(cs)) {
compute_partition_effective_cpumask(cs, &new_cpus);
-
- if (remote && cpumask_empty(&new_cpus) &&
- partition_is_populated(cs, NULL)) {
- cs->prs_err = PERR_HOTPLUG;
- remote_partition_disable(cs, tmp);
- compute_effective_cpumask(&new_cpus, cs, parent);
- remote = false;
+ if (cpumask_empty(&new_cpus) &&
+ partition_is_populated(cs, NULL)) {
+ cs->prs_err = PERR_HOTPLUG;
+ remote_partition_disable(cs, tmp);
+ compute_effective_cpumask(&new_cpus, cs, parent);
+ }
+ goto update_tasks;
}
/*
@@ -3913,28 +3902,24 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
* the following conditions hold:
* 1) empty effective cpus but not valid empty partition.
* 2) parent is invalid or doesn't grant any cpus to child
- * partitions.
- */
- if (is_local_partition(cs) && (!is_partition_valid(parent) ||
- tasks_nocpu_error(parent, cs, &new_cpus))) {
- partcmd = partcmd_invalidate;
- local_partition_invalidate(cs, tmp);
- }
- /*
+ * partitions.
+ *
* On the other hand, an invalid partition root may be transitioned
* back to a regular one with a non-empty user xcpus.
+ *
+ * local_partition_update can handle these cases.
*/
- else if (is_partition_valid(parent) && is_partition_invalid(cs) &&
- !cpumask_empty(user_xcpus(cs))) {
- partcmd = partcmd_update;
- local_partition_update(cs, tmp);
- }
- if (partcmd >= 0) {
- if ((partcmd == partcmd_invalidate) || is_partition_valid(cs)) {
- compute_partition_effective_cpumask(cs, &new_cpus);
- cpuset_force_rebuild();
- }
- }
+ local_partition_update(cs, tmp);
+
+ /*
+ * Recompute effective CPU mask after partition state update:
+ * - For valid partitions: calculate partition-specific effective CPUs
+ * - For invalid partitions: compute member effective CPU mask
+ */
+ if (is_partition_valid(cs))
+ compute_partition_effective_cpumask(cs, &new_cpus);
+ else
+ compute_effective_cpumask(&new_cpus, cs, parent);
update_tasks:
cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);
--
2.34.1
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