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Message-ID: <20250829154814.47015-15-frederic@kernel.org>
Date: Fri, 29 Aug 2025 17:47:55 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Frederic Weisbecker <frederic@...nel.org>,
Michal Koutný <mkoutny@...e.com>,
Ingo Molnar <mingo@...hat.com>,
Johannes Weiner <hannes@...xchg.org>,
Marco Crivellari <marco.crivellari@...e.com>,
Michal Hocko <mhocko@...e.com>,
Peter Zijlstra <peterz@...radead.org>,
Tejun Heo <tj@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Vlastimil Babka <vbabka@...e.cz>,
Waiman Long <longman@...hat.com>,
cgroups@...r.kernel.org
Subject: [PATCH 14/33] cpuset: Update HK_TYPE_DOMAIN cpumask from cpuset
Until now, HK_TYPE_DOMAIN used to only include boot defined isolated
CPUs passed through isolcpus= boot option. Users interested in also
knowing the runtime defined isolated CPUs through cpuset must use
different APIs: cpuset_cpu_is_isolated(), cpu_is_isolated(), etc...
There are many drawbacks to that approach:
1) Most interested subsystems want to know about all isolated CPUs, not
just those defined on boot time.
2) cpuset_cpu_is_isolated() / cpu_is_isolated() are not synchronized with
concurrent cpuset changes.
3) Further cpuset modifications are not propagated to subsystems
Solve 1) and 2) and centralize all isolated CPUs within the
HK_TYPE_DOMAIN housekeeping cpumask.
Subsystems can rely on RCU to synchronize against concurrent changes.
The propagation mentioned in 3) will be handled in further patches.
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
---
include/linux/sched/isolation.h | 4 +-
kernel/cgroup/cpuset.c | 2 +
kernel/sched/isolation.c | 65 ++++++++++++++++++++++++++++++---
kernel/sched/sched.h | 1 +
4 files changed, 65 insertions(+), 7 deletions(-)
diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index 9262378760b1..199d0fc4646f 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -36,12 +36,13 @@ extern bool housekeeping_test_cpu(int cpu, enum hk_type type);
static inline bool housekeeping_cpu(int cpu, enum hk_type type)
{
- if (housekeeping_flags & BIT(type))
+ if (READ_ONCE(housekeeping_flags) & BIT(type))
return housekeeping_test_cpu(cpu, type);
else
return true;
}
+extern int housekeeping_update(struct cpumask *mask, enum hk_type type);
extern void __init housekeeping_init(void);
#else
@@ -74,6 +75,7 @@ static inline bool housekeeping_cpu(int cpu, enum hk_type type)
return true;
}
+static inline int housekeeping_update(struct cpumask *mask, enum hk_type type) { return 0; }
static inline void housekeeping_init(void) { }
#endif /* CONFIG_CPU_ISOLATION */
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 2d2fc74bc00c..4f2bc68332a7 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1351,6 +1351,8 @@ static void update_unbound_workqueue_cpumask(bool isolcpus_updated)
ret = workqueue_unbound_exclude_cpumask(isolated_cpus);
WARN_ON_ONCE(ret < 0);
+ ret = housekeeping_update(isolated_cpus, HK_TYPE_DOMAIN);
+ WARN_ON_ONCE(ret < 0);
}
/**
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 5ddb8dc5ca91..48f3b6b20604 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -23,16 +23,39 @@ EXPORT_SYMBOL_GPL(housekeeping_flags);
bool housekeeping_enabled(enum hk_type type)
{
- return !!(housekeeping_flags & BIT(type));
+ return !!(READ_ONCE(housekeeping_flags) & BIT(type));
}
EXPORT_SYMBOL_GPL(housekeeping_enabled);
+static bool housekeeping_dereference_check(enum hk_type type)
+{
+ if (type == HK_TYPE_DOMAIN) {
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU) && lockdep_is_cpus_write_held())
+ return true;
+ if (IS_ENABLED(CONFIG_CPUSETS) && lockdep_is_cpuset_held())
+ return true;
+
+ return false;
+ }
+
+ return true;
+}
+
+static inline struct cpumask *__housekeeping_cpumask(enum hk_type type)
+{
+ return rcu_dereference_check(housekeeping_cpumasks[type],
+ housekeeping_dereference_check(type));
+}
+
const struct cpumask *housekeeping_cpumask(enum hk_type type)
{
- if (housekeeping_flags & BIT(type)) {
- return rcu_dereference_check(housekeeping_cpumasks[type], 1);
- }
- return cpu_possible_mask;
+ const struct cpumask *mask = NULL;
+
+ if (READ_ONCE(housekeeping_flags) & BIT(type))
+ mask = __housekeeping_cpumask(type);
+ if (!mask)
+ mask = cpu_possible_mask;
+ return mask;
}
EXPORT_SYMBOL_GPL(housekeeping_cpumask);
@@ -70,12 +93,42 @@ EXPORT_SYMBOL_GPL(housekeeping_affine);
bool housekeeping_test_cpu(int cpu, enum hk_type type)
{
- if (housekeeping_flags & BIT(type))
+ if (READ_ONCE(housekeeping_flags) & BIT(type))
return cpumask_test_cpu(cpu, housekeeping_cpumask(type));
return true;
}
EXPORT_SYMBOL_GPL(housekeeping_test_cpu);
+int housekeeping_update(struct cpumask *mask, enum hk_type type)
+{
+ struct cpumask *trial, *old = NULL;
+
+ if (type != HK_TYPE_DOMAIN)
+ return -ENOTSUPP;
+
+ trial = kmalloc(sizeof(*trial), GFP_KERNEL);
+ if (!trial)
+ return -ENOMEM;
+
+ cpumask_andnot(trial, housekeeping_cpumask(HK_TYPE_DOMAIN_BOOT), mask);
+ if (!cpumask_intersects(trial, cpu_online_mask)) {
+ kfree(trial);
+ return -EINVAL;
+ }
+
+ if (housekeeping_flags & BIT(type))
+ old = __housekeeping_cpumask(type);
+ else
+ WRITE_ONCE(housekeeping_flags, housekeeping_flags | BIT(type));
+ rcu_assign_pointer(housekeeping_cpumasks[type], trial);
+
+ synchronize_rcu();
+
+ kfree(old);
+
+ return 0;
+}
+
void __init housekeeping_init(void)
{
enum hk_type type;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 0b1a233dcabf..d3512138027b 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -30,6 +30,7 @@
#include <linux/context_tracking.h>
#include <linux/cpufreq.h>
#include <linux/cpumask_api.h>
+#include <linux/cpuset.h>
#include <linux/ctype.h>
#include <linux/file.h>
#include <linux/fs_api.h>
--
2.51.0
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