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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 12/33] sched/isolation: Convert housekeeping cpumasks to rcu pointers Date: Mon, 13 Oct 2025 22:31:25 +0200 Message-ID: <20251013203146.10162-13-frederic@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251013203146.10162-1-frederic@kernel.org> References: <20251013203146.10162-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Stat-Signature: tbbkbxxbqfxooz1wst6jz8cf3udrng6m X-Rspam-User: X-Rspamd-Queue-Id: 49126A0007 X-HE-Tag: 1760387614-706940 X-HE-Meta: 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 i+/Hw1fR 7M1+3zNpvMj4kkoMZaISLsj8NceAbolIsUgNPIKJIJTGeZOionRxoyO3ulQOpqGxcxXaKGb2XxsMV2n68Uc4dRCsQxWSlvk1vhsBO+rYGRKVigPp5j3ZUCPuIxgjS6z9spVsIVH+shMNJ85vwL38u4fqJSffIs15Ulyv0pa64GguGm4bJi7taWY1QOY4AZe+X26sezTHdC9FPtuG4Rla+f4fOq+PBWemK4CJj8gD04vtKU2IxrMImZQrU9rhuOXeJyzWAlw+HfGunOgM= 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 modifyable 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 | 58 +++++++++++++++++++++++++--------------- kernel/sched/sched.h | 1 + 2 files changed, 37 insertions(+), 22 deletions(-) diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 8690fb705089..b46c20b5437f 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 (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; } diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 1f5d07067f60..0c0ef8999fd6 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -42,6 +42,7 @@ #include #include #include +#include #include #include #include -- 2.51.0