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b1c7ba1bab
commit 6575820221 upstream.
Currently, all workqueue cpu hotplug operations run off
CPU_PRI_WORKQUEUE which is higher than normal notifiers. This is to
ensure that workqueue is up and running while bringing up a CPU before
other notifiers try to use workqueue on the CPU.
Per-cpu workqueues are supposed to remain working and bound to the CPU
for normal CPU_DOWN_PREPARE notifiers. This holds mostly true even
with workqueue offlining running with higher priority because
workqueue CPU_DOWN_PREPARE only creates a bound trustee thread which
runs the per-cpu workqueue without concurrency management without
explicitly detaching the existing workers.
However, if the trustee needs to create new workers, it creates
unbound workers which may wander off to other CPUs while
CPU_DOWN_PREPARE notifiers are in progress. Furthermore, if the CPU
down is cancelled, the per-CPU workqueue may end up with workers which
aren't bound to the CPU.
While reliably reproducible with a convoluted artificial test-case
involving scheduling and flushing CPU burning work items from CPU down
notifiers, this isn't very likely to happen in the wild, and, even
when it happens, the effects are likely to be hidden by the following
successful CPU down.
Fix it by using different priorities for up and down notifiers - high
priority for up operations and low priority for down operations.
Workqueue cpu hotplug operations will soon go through further cleanup.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
179 lines
5.0 KiB
C
179 lines
5.0 KiB
C
/*
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* include/linux/cpu.h - generic cpu definition
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*
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* This is mainly for topological representation. We define the
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* basic 'struct cpu' here, which can be embedded in per-arch
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* definitions of processors.
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*
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* Basic handling of the devices is done in drivers/base/cpu.c
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* and system devices are handled in drivers/base/sys.c.
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*
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* CPUs are exported via sysfs in the class/cpu/devices/
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* directory.
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*/
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#ifndef _LINUX_CPU_H_
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#define _LINUX_CPU_H_
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#include <linux/sysdev.h>
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#include <linux/node.h>
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#include <linux/compiler.h>
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#include <linux/cpumask.h>
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struct cpu {
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int node_id; /* The node which contains the CPU */
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int hotpluggable; /* creates sysfs control file if hotpluggable */
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struct sys_device sysdev;
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};
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extern int register_cpu(struct cpu *cpu, int num);
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extern struct sys_device *get_cpu_sysdev(unsigned cpu);
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extern int cpu_add_sysdev_attr(struct sysdev_attribute *attr);
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extern void cpu_remove_sysdev_attr(struct sysdev_attribute *attr);
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extern int cpu_add_sysdev_attr_group(struct attribute_group *attrs);
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extern void cpu_remove_sysdev_attr_group(struct attribute_group *attrs);
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extern int sched_create_sysfs_power_savings_entries(struct sysdev_class *cls);
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#ifdef CONFIG_HOTPLUG_CPU
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extern void unregister_cpu(struct cpu *cpu);
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extern ssize_t arch_cpu_probe(const char *, size_t);
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extern ssize_t arch_cpu_release(const char *, size_t);
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#endif
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struct notifier_block;
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/*
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* CPU notifier priorities.
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*/
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enum {
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/*
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* SCHED_ACTIVE marks a cpu which is coming up active during
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* CPU_ONLINE and CPU_DOWN_FAILED and must be the first
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* notifier. CPUSET_ACTIVE adjusts cpuset according to
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* cpu_active mask right after SCHED_ACTIVE. During
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* CPU_DOWN_PREPARE, SCHED_INACTIVE and CPUSET_INACTIVE are
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* ordered in the similar way.
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*
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* This ordering guarantees consistent cpu_active mask and
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* migration behavior to all cpu notifiers.
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*/
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CPU_PRI_SCHED_ACTIVE = INT_MAX,
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CPU_PRI_CPUSET_ACTIVE = INT_MAX - 1,
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CPU_PRI_SCHED_INACTIVE = INT_MIN + 1,
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CPU_PRI_CPUSET_INACTIVE = INT_MIN,
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/* migration should happen before other stuff but after perf */
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CPU_PRI_PERF = 20,
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CPU_PRI_MIGRATION = 10,
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/* bring up workqueues before normal notifiers and down after */
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CPU_PRI_WORKQUEUE_UP = 5,
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CPU_PRI_WORKQUEUE_DOWN = -5,
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};
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#ifdef CONFIG_SMP
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/* Need to know about CPUs going up/down? */
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#if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE)
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#define cpu_notifier(fn, pri) { \
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static struct notifier_block fn##_nb __cpuinitdata = \
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{ .notifier_call = fn, .priority = pri }; \
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register_cpu_notifier(&fn##_nb); \
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}
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#else /* #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */
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#define cpu_notifier(fn, pri) do { (void)(fn); } while (0)
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#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */
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#ifdef CONFIG_HOTPLUG_CPU
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extern int register_cpu_notifier(struct notifier_block *nb);
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extern void unregister_cpu_notifier(struct notifier_block *nb);
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#else
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#ifndef MODULE
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extern int register_cpu_notifier(struct notifier_block *nb);
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#else
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static inline int register_cpu_notifier(struct notifier_block *nb)
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{
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return 0;
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}
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#endif
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static inline void unregister_cpu_notifier(struct notifier_block *nb)
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{
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}
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#endif
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int cpu_up(unsigned int cpu);
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void notify_cpu_starting(unsigned int cpu);
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extern void cpu_maps_update_begin(void);
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extern void cpu_maps_update_done(void);
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#else /* CONFIG_SMP */
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#define cpu_notifier(fn, pri) do { (void)(fn); } while (0)
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static inline int register_cpu_notifier(struct notifier_block *nb)
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{
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return 0;
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}
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static inline void unregister_cpu_notifier(struct notifier_block *nb)
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{
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}
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static inline void cpu_maps_update_begin(void)
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{
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}
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static inline void cpu_maps_update_done(void)
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{
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}
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#endif /* CONFIG_SMP */
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extern struct sysdev_class cpu_sysdev_class;
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#ifdef CONFIG_HOTPLUG_CPU
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/* Stop CPUs going up and down. */
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extern void get_online_cpus(void);
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extern void put_online_cpus(void);
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#define hotcpu_notifier(fn, pri) cpu_notifier(fn, pri)
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#define register_hotcpu_notifier(nb) register_cpu_notifier(nb)
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#define unregister_hotcpu_notifier(nb) unregister_cpu_notifier(nb)
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int cpu_down(unsigned int cpu);
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#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
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extern void cpu_hotplug_driver_lock(void);
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extern void cpu_hotplug_driver_unlock(void);
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#else
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static inline void cpu_hotplug_driver_lock(void)
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{
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}
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static inline void cpu_hotplug_driver_unlock(void)
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{
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}
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#endif
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#else /* CONFIG_HOTPLUG_CPU */
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#define get_online_cpus() do { } while (0)
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#define put_online_cpus() do { } while (0)
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#define hotcpu_notifier(fn, pri) do { (void)(fn); } while (0)
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/* These aren't inline functions due to a GCC bug. */
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#define register_hotcpu_notifier(nb) ({ (void)(nb); 0; })
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#define unregister_hotcpu_notifier(nb) ({ (void)(nb); })
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#endif /* CONFIG_HOTPLUG_CPU */
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#ifdef CONFIG_PM_SLEEP_SMP
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extern int suspend_cpu_hotplug;
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extern int disable_nonboot_cpus(void);
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extern void enable_nonboot_cpus(void);
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#else /* !CONFIG_PM_SLEEP_SMP */
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#define suspend_cpu_hotplug 0
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static inline int disable_nonboot_cpus(void) { return 0; }
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static inline void enable_nonboot_cpus(void) {}
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#endif /* !CONFIG_PM_SLEEP_SMP */
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#endif /* _LINUX_CPU_H_ */
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