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e93ad19d05
If "cpuset.memory_migrate" is set, when a process is moved from one cpuset to another with a different memory node mask, pages in used by the process are migrated to the new set of nodes. This was performed synchronously in the ->attach() callback, which is synchronized against process management. Recently, the synchronization was changed from per-process rwsem to global percpu rwsem for simplicity and optimization. Combined with the synchronous mm migration, this led to deadlocks because mm migration could schedule a work item which may in turn try to create a new worker blocking on the process management lock held from cgroup process migration path. This heavy an operation shouldn't be performed synchronously from that deep inside cgroup migration in the first place. This patch punts the actual migration to an ordered workqueue and updates cgroup process migration and cpuset config update paths to flush the workqueue after all locks are released. This way, the operations still seem synchronous to userland without entangling mm migration with process management synchronization. CPU hotplug can also invoke mm migration but there's no reason for it to wait for mm migrations and thus doesn't synchronize against their completions. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-tested-by: Christian Borntraeger <borntraeger@de.ibm.com> Cc: stable@vger.kernel.org # v4.4+
255 lines
5.8 KiB
C
255 lines
5.8 KiB
C
#ifndef _LINUX_CPUSET_H
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#define _LINUX_CPUSET_H
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/*
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* cpuset interface
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*
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* Copyright (C) 2003 BULL SA
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* Copyright (C) 2004-2006 Silicon Graphics, Inc.
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*
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*/
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#include <linux/sched.h>
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#include <linux/cpumask.h>
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#include <linux/nodemask.h>
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#include <linux/mm.h>
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#include <linux/jump_label.h>
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#ifdef CONFIG_CPUSETS
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extern struct static_key cpusets_enabled_key;
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static inline bool cpusets_enabled(void)
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{
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return static_key_false(&cpusets_enabled_key);
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}
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static inline int nr_cpusets(void)
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{
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/* jump label reference count + the top-level cpuset */
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return static_key_count(&cpusets_enabled_key) + 1;
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}
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static inline void cpuset_inc(void)
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{
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static_key_slow_inc(&cpusets_enabled_key);
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}
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static inline void cpuset_dec(void)
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{
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static_key_slow_dec(&cpusets_enabled_key);
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}
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extern int cpuset_init(void);
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extern void cpuset_init_smp(void);
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extern void cpuset_update_active_cpus(bool cpu_online);
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extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
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extern void cpuset_cpus_allowed_fallback(struct task_struct *p);
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extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
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#define cpuset_current_mems_allowed (current->mems_allowed)
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void cpuset_init_current_mems_allowed(void);
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int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask);
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extern int __cpuset_node_allowed(int node, gfp_t gfp_mask);
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static inline int cpuset_node_allowed(int node, gfp_t gfp_mask)
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{
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return nr_cpusets() <= 1 || __cpuset_node_allowed(node, gfp_mask);
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}
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static inline int cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask)
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{
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return cpuset_node_allowed(zone_to_nid(z), gfp_mask);
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}
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extern int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
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const struct task_struct *tsk2);
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#define cpuset_memory_pressure_bump() \
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do { \
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if (cpuset_memory_pressure_enabled) \
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__cpuset_memory_pressure_bump(); \
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} while (0)
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extern int cpuset_memory_pressure_enabled;
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extern void __cpuset_memory_pressure_bump(void);
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extern void cpuset_task_status_allowed(struct seq_file *m,
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struct task_struct *task);
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extern int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,
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struct pid *pid, struct task_struct *tsk);
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extern int cpuset_mem_spread_node(void);
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extern int cpuset_slab_spread_node(void);
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static inline int cpuset_do_page_mem_spread(void)
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{
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return task_spread_page(current);
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}
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static inline int cpuset_do_slab_mem_spread(void)
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{
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return task_spread_slab(current);
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}
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extern int current_cpuset_is_being_rebound(void);
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extern void rebuild_sched_domains(void);
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extern void cpuset_print_current_mems_allowed(void);
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/*
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* read_mems_allowed_begin is required when making decisions involving
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* mems_allowed such as during page allocation. mems_allowed can be updated in
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* parallel and depending on the new value an operation can fail potentially
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* causing process failure. A retry loop with read_mems_allowed_begin and
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* read_mems_allowed_retry prevents these artificial failures.
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*/
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static inline unsigned int read_mems_allowed_begin(void)
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{
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if (!cpusets_enabled())
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return 0;
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return read_seqcount_begin(¤t->mems_allowed_seq);
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}
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/*
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* If this returns true, the operation that took place after
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* read_mems_allowed_begin may have failed artificially due to a concurrent
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* update of mems_allowed. It is up to the caller to retry the operation if
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* appropriate.
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*/
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static inline bool read_mems_allowed_retry(unsigned int seq)
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{
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if (!cpusets_enabled())
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return false;
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return read_seqcount_retry(¤t->mems_allowed_seq, seq);
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}
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static inline void set_mems_allowed(nodemask_t nodemask)
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{
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unsigned long flags;
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task_lock(current);
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local_irq_save(flags);
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write_seqcount_begin(¤t->mems_allowed_seq);
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current->mems_allowed = nodemask;
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write_seqcount_end(¤t->mems_allowed_seq);
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local_irq_restore(flags);
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task_unlock(current);
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}
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extern void cpuset_post_attach_flush(void);
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#else /* !CONFIG_CPUSETS */
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static inline bool cpusets_enabled(void) { return false; }
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static inline int cpuset_init(void) { return 0; }
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static inline void cpuset_init_smp(void) {}
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static inline void cpuset_update_active_cpus(bool cpu_online)
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{
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partition_sched_domains(1, NULL, NULL);
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}
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static inline void cpuset_cpus_allowed(struct task_struct *p,
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struct cpumask *mask)
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{
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cpumask_copy(mask, cpu_possible_mask);
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}
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static inline void cpuset_cpus_allowed_fallback(struct task_struct *p)
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{
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}
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static inline nodemask_t cpuset_mems_allowed(struct task_struct *p)
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{
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return node_possible_map;
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}
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#define cpuset_current_mems_allowed (node_states[N_MEMORY])
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static inline void cpuset_init_current_mems_allowed(void) {}
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static inline int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask)
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{
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return 1;
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}
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static inline int cpuset_node_allowed(int node, gfp_t gfp_mask)
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{
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return 1;
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}
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static inline int cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask)
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{
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return 1;
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}
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static inline int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
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const struct task_struct *tsk2)
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{
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return 1;
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}
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static inline void cpuset_memory_pressure_bump(void) {}
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static inline void cpuset_task_status_allowed(struct seq_file *m,
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struct task_struct *task)
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{
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}
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static inline int cpuset_mem_spread_node(void)
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{
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return 0;
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}
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static inline int cpuset_slab_spread_node(void)
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{
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return 0;
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}
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static inline int cpuset_do_page_mem_spread(void)
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{
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return 0;
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}
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static inline int cpuset_do_slab_mem_spread(void)
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{
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return 0;
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}
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static inline int current_cpuset_is_being_rebound(void)
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{
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return 0;
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}
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static inline void rebuild_sched_domains(void)
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{
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partition_sched_domains(1, NULL, NULL);
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}
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static inline void cpuset_print_current_mems_allowed(void)
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{
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}
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static inline void set_mems_allowed(nodemask_t nodemask)
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{
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}
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static inline unsigned int read_mems_allowed_begin(void)
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{
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return 0;
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}
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static inline bool read_mems_allowed_retry(unsigned int seq)
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{
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return false;
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}
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static inline void cpuset_post_attach_flush(void)
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{
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}
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#endif /* !CONFIG_CPUSETS */
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#endif /* _LINUX_CPUSET_H */
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