[PATCH 13/33] cpuset: Update HK_TYPE_DOMAIN cpumask from cpuset
From: Frederic Weisbecker <frederic@kernel.org>
Date: 2025-10-13 20:33:41
Also in:
cgroups, linux-arm-kernel, linux-block, linux-mm, linux-pci, lkml
Subsystem:
control group (cgroup), control group - cpuset, scheduler, the rest · Maintainers:
Tejun Heo, Johannes Weiner, Michal Koutný, Waiman Long, Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot, Linus Torvalds
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@kernel.org> --- include/linux/sched/isolation.h | 2 + kernel/cgroup/cpuset.c | 2 + kernel/sched/isolation.c | 75 ++++++++++++++++++++++++++++++--- kernel/sched/sched.h | 1 + 4 files changed, 74 insertions(+), 6 deletions(-)
diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index da22b038942a..94d5c835121b 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h@@ -32,6 +32,7 @@ extern const struct cpumask *housekeeping_cpumask(enum hk_type type); extern bool housekeeping_enabled(enum hk_type type); extern void housekeeping_affine(struct task_struct *t, enum hk_type type); extern bool housekeeping_test_cpu(int cpu, enum hk_type type); +extern int housekeeping_update(struct cpumask *mask, enum hk_type type); extern void __init housekeeping_init(void); #else
@@ -59,6 +60,7 @@ static inline bool housekeeping_test_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 aa1ac7bcf2ea..b04a4242f2fa 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c@@ -1403,6 +1403,8 @@ 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 b46c20b5437f..95d69c2102f6 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c@@ -29,18 +29,48 @@ static struct housekeeping housekeeping; 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 (IS_ENABLED(CONFIG_LOCKDEP) && type == HK_TYPE_DOMAIN) { + /* Cpuset isn't even writable yet? */ + if (system_state <= SYSTEM_SCHEDULING) + return true; + + /* CPU hotplug write locked, so cpuset partition can't be overwritten */ + if (IS_ENABLED(CONFIG_HOTPLUG_CPU) && lockdep_is_cpus_write_held()) + return true; + + /* Cpuset lock held, partitions not writable */ + if (IS_ENABLED(CONFIG_CPUSETS) && lockdep_is_cpuset_held()) + return true; + + return false; + } + + return true; +} + +static inline struct cpumask *housekeeping_cpumask_dereference(enum hk_type type) +{ + return rcu_dereference_check(housekeeping.cpumasks[type], + housekeeping_dereference_check(type)); +} + const struct cpumask *housekeeping_cpumask(enum hk_type type) { + const struct cpumask *mask = NULL; + if (static_branch_unlikely(&housekeeping_overridden)) { - if (housekeeping.flags & BIT(type)) { - return rcu_dereference_check(housekeeping.cpumasks[type], 1); - } + if (READ_ONCE(housekeeping.flags) & BIT(type)) + mask = housekeeping_cpumask_dereference(type); } - return cpu_possible_mask; + if (!mask) + mask = cpu_possible_mask; + return mask; } EXPORT_SYMBOL_GPL(housekeeping_cpumask);
@@ -80,12 +110,45 @@ 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) + static_branch_enable(&housekeeping_overridden); + + if (!(housekeeping.flags & BIT(type))) + old = housekeeping_cpumask_dereference(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 0c0ef8999fd6..8fac8aa451c6 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>
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2.51.0