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Miller" , Eric Dumazet , Gabriele Monaco , Greg Kroah-Hartman , Ingo Molnar , Jakub Kicinski , Jens Axboe , Johannes Weiner , Lai Jiangshan , Marco Crivellari , Michal Hocko , Muchun Song , Paolo Abeni , Peter Zijlstra , Phil Auld , "Rafael J . Wysocki" , Roman Gushchin , Shakeel Butt , Simon Horman , Tejun Heo , Thomas Gleixner , Vlastimil Babka , Waiman Long , Will Deacon , cgroups@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH 13/33] sched/isolation: Convert housekeeping cpumasks to rcu pointers Date: Sun, 25 Jan 2026 23:45:20 +0100 Message-ID: <20260125224541.50226-14-frederic@kernel.org> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20260125224541.50226-1-frederic@kernel.org> References: <20260125224541.50226-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 411BD180008 X-Stat-Signature: gwmz79fio8eycr9st5n1jr31rt7exw76 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1769381258-937317 X-HE-Meta: U2FsdGVkX18nspL99SjTp+zTXzpkIbEy6Pc25JSorAj3vV6BDAVd9ABsUrOGDvhQZGnAlQCGE9d1vIdNRUXmrQ6DK9YtU37i+D5P5DRjQb862pMsmqp5/BCFTppafLBDwycW0iusGVY6MdP+1V2oK6sLvMXh9v2rjdjpHpVDrF/ihjhxDnx/iANbqYcQjV6TQqdavh9KAddpELyldP0bfggkbGRwkTSk7f0LIWD4Iu1B+Job1LwEpKLou+wlzWw20YH9jdBq70IEflnW0+dy+2vk1QyuaioKJUvPfUCRfSHpiBZxlUgRYn4XgnPg7PEB7lG5XjybRtx/exD2Tbnvz1nKScieATa80MH5mCDdrEZh0pl44TAP6OQmIjlq37zhit4vG4wt4IGKAUhUsj9Xh+SVKWxNZNinfXhI5qEW/mwTMd4tXNOePqwDL4KjVW+/KRBlWeh+bSYZlvysCe8w70Pp4JzSi2PLCfJbI7Ooc61ezQBt47QOg/SmcBCSNYRs9eDOt8e+CHfGn8XVv7aoXazdwF9FwRn3OU5NFAw0FqL3kXryaubehpZOdkG93YwJtsn4oUHYuk2ajro7UUbJ0j4xQrm5XzlUOK6DKQsxrtiI/7P3Yv7mBaNlhCcTd51spXyDFk4T1GVGROJQEsuLYl63uxQPclKcV5VLomohKkugbpPJY58U2OG466JI5Ji17IAroHNpV3NTKPDRqox6OUc7sTrvrRg/adY0cBZKC56ZFIs05wp1UHwMwd0tjgG/ZzdomFLS8R/QN5G3OWBA6tn86SAs9cks31He8sej1AweShptAwS1Nlj4kF5YgB29bPhPDK5GErJiRDmY/A8KjwXwpGLBzFP/ttu3uB25rfbj+26Ybpme6CyED+amtV+fbGEylXZREbnPgshmoZkwtOWiJWPCcdSc1Bgko/jN5v+CWNxUY30WJOU3ubwEXKnF488QIW/2zOxZ7itk5xl lcoM9bEe EM+C4zphs0hA7v5WCmaG6+/xKFCGgm5O8ajAfYvPkv/rwDDfxd+h3ssQzeIsrfxUOFO/QHlFPAjPPfAAeRwSSbu8Pj5LSuVYm2Mpo3B/MOZ2XckKUdqFEyYGDg5h8gRwpU+fc8AdsofIPYcM3pNa6Hk5hl5/qC+h9lrt+lEyjJEtvFx2RL4dLNuNZ6ohB7dzRefYvo3p5n6rbw9m3nilQYetFT7KVua0BAM1XZB3+oY478YTLHyaJbCz+cD+eZ18jZCaujV+/0V4NDAU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: HK_TYPE_DOMAIN's cpumask will soon be made modifiable by cpuset. A synchronization mechanism is then needed to synchronize the updates with the housekeeping cpumask readers. Turn the housekeeping cpumasks into RCU pointers. Once a housekeeping cpumask will be modified, the update side will wait for an RCU grace period and propagate the change to interested subsystem when deemed necessary. Signed-off-by: Frederic Weisbecker --- kernel/sched/isolation.c | 60 +++++++++++++++++++++++++--------------- kernel/sched/sched.h | 1 + 2 files changed, 38 insertions(+), 23 deletions(-) diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 11a623fa6320..6f77289c14c3 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -21,7 +21,7 @@ DEFINE_STATIC_KEY_FALSE(housekeeping_overridden); EXPORT_SYMBOL_GPL(housekeeping_overridden); struct housekeeping { - cpumask_var_t cpumasks[HK_TYPE_MAX]; + struct cpumask __rcu *cpumasks[HK_TYPE_MAX]; unsigned long flags; }; @@ -33,17 +33,28 @@ bool housekeeping_enabled(enum hk_type type) } EXPORT_SYMBOL_GPL(housekeeping_enabled); +const struct cpumask *housekeeping_cpumask(enum hk_type type) +{ + if (static_branch_unlikely(&housekeeping_overridden)) { + if (housekeeping.flags & BIT(type)) { + return rcu_dereference_check(housekeeping.cpumasks[type], 1); + } + } + return cpu_possible_mask; +} +EXPORT_SYMBOL_GPL(housekeeping_cpumask); + int housekeeping_any_cpu(enum hk_type type) { int cpu; if (static_branch_unlikely(&housekeeping_overridden)) { if (housekeeping.flags & BIT(type)) { - cpu = sched_numa_find_closest(housekeeping.cpumasks[type], smp_processor_id()); + cpu = sched_numa_find_closest(housekeeping_cpumask(type), smp_processor_id()); if (cpu < nr_cpu_ids) return cpu; - cpu = cpumask_any_and_distribute(housekeeping.cpumasks[type], cpu_online_mask); + cpu = cpumask_any_and_distribute(housekeeping_cpumask(type), cpu_online_mask); if (likely(cpu < nr_cpu_ids)) return cpu; /* @@ -59,28 +70,18 @@ int housekeeping_any_cpu(enum hk_type type) } EXPORT_SYMBOL_GPL(housekeeping_any_cpu); -const struct cpumask *housekeeping_cpumask(enum hk_type type) -{ - if (static_branch_unlikely(&housekeeping_overridden)) - if (housekeeping.flags & BIT(type)) - return housekeeping.cpumasks[type]; - return cpu_possible_mask; -} -EXPORT_SYMBOL_GPL(housekeeping_cpumask); - void housekeeping_affine(struct task_struct *t, enum hk_type type) { if (static_branch_unlikely(&housekeeping_overridden)) if (housekeeping.flags & BIT(type)) - set_cpus_allowed_ptr(t, housekeeping.cpumasks[type]); + set_cpus_allowed_ptr(t, housekeeping_cpumask(type)); } EXPORT_SYMBOL_GPL(housekeeping_affine); bool housekeeping_test_cpu(int cpu, enum hk_type type) { - if (static_branch_unlikely(&housekeeping_overridden)) - if (housekeeping.flags & BIT(type)) - return cpumask_test_cpu(cpu, housekeeping.cpumasks[type]); + if (static_branch_unlikely(&housekeeping_overridden) && housekeeping.flags & BIT(type)) + return cpumask_test_cpu(cpu, housekeeping_cpumask(type)); return true; } EXPORT_SYMBOL_GPL(housekeeping_test_cpu); @@ -96,20 +97,33 @@ void __init housekeeping_init(void) if (housekeeping.flags & HK_FLAG_KERNEL_NOISE) sched_tick_offload_init(); - + /* + * Realloc with a proper allocator so that any cpumask update + * can indifferently free the old version with kfree(). + */ for_each_set_bit(type, &housekeeping.flags, HK_TYPE_MAX) { + struct cpumask *omask, *nmask = kmalloc(cpumask_size(), GFP_KERNEL); + + if (WARN_ON_ONCE(!nmask)) + return; + + omask = rcu_dereference(housekeeping.cpumasks[type]); + /* We need at least one CPU to handle housekeeping work */ - WARN_ON_ONCE(cpumask_empty(housekeeping.cpumasks[type])); + WARN_ON_ONCE(cpumask_empty(omask)); + cpumask_copy(nmask, omask); + RCU_INIT_POINTER(housekeeping.cpumasks[type], nmask); + memblock_free(omask, cpumask_size()); } } static void __init housekeeping_setup_type(enum hk_type type, cpumask_var_t housekeeping_staging) { + struct cpumask *mask = memblock_alloc_or_panic(cpumask_size(), SMP_CACHE_BYTES); - alloc_bootmem_cpumask_var(&housekeeping.cpumasks[type]); - cpumask_copy(housekeeping.cpumasks[type], - housekeeping_staging); + cpumask_copy(mask, housekeeping_staging); + RCU_INIT_POINTER(housekeeping.cpumasks[type], mask); } static int __init housekeeping_setup(char *str, unsigned long flags) @@ -162,7 +176,7 @@ static int __init housekeeping_setup(char *str, unsigned long flags) for_each_set_bit(type, &iter_flags, HK_TYPE_MAX) { if (!cpumask_equal(housekeeping_staging, - housekeeping.cpumasks[type])) { + housekeeping_cpumask(type))) { pr_warn("Housekeeping: nohz_full= must match isolcpus=\n"); goto free_housekeeping_staging; } @@ -183,7 +197,7 @@ static int __init housekeeping_setup(char *str, unsigned long flags) iter_flags = flags & (HK_FLAG_KERNEL_NOISE | HK_FLAG_DOMAIN); first_cpu = (type == HK_TYPE_MAX || !iter_flags) ? 0 : cpumask_first_and_and(cpu_present_mask, - housekeeping_staging, housekeeping.cpumasks[type]); + housekeeping_staging, housekeeping_cpumask(type)); if (first_cpu >= min(nr_cpu_ids, setup_max_cpus)) { pr_warn("Housekeeping: must include one present CPU " "neither in nohz_full= nor in isolcpus=domain, " diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index d30cca6870f5..475bdab3b8db 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -42,6 +42,7 @@ #include #include #include +#include #include #include #include -- 2.51.1