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9ea09af3bd
Introduce stop_machine_create/destroy. With this interface subsystems that need a non-failing stop_machine environment can create the stop_machine machine threads before actually calling stop_machine. When the threads aren't needed anymore they can be killed with stop_machine_destroy again. When stop_machine gets called and the threads aren't present they will be created and destroyed automatically. This restores the old behaviour of stop_machine. This patch also converts cpu hotplug to the new interface since it is special: cpu_down calls __stop_machine instead of stop_machine. However the kstop threads will only be created when stop_machine gets called. Changing the code so that the threads would be created automatically on __stop_machine is currently not possible: when __stop_machine gets called we hold cpu_add_remove_lock, which is the same lock that create_rt_workqueue would take. So the workqueue needs to be created before the cpu hotplug code locks cpu_add_remove_lock. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
73 lines
2.3 KiB
C
73 lines
2.3 KiB
C
#ifndef _LINUX_STOP_MACHINE
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#define _LINUX_STOP_MACHINE
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/* "Bogolock": stop the entire machine, disable interrupts. This is a
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very heavy lock, which is equivalent to grabbing every spinlock
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(and more). So the "read" side to such a lock is anything which
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disables preeempt. */
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#include <linux/cpu.h>
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#include <linux/cpumask.h>
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#include <asm/system.h>
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#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
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/**
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* stop_machine: freeze the machine on all CPUs and run this function
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* @fn: the function to run
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* @data: the data ptr for the @fn()
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* @cpus: the cpus to run the @fn() on (NULL = any online cpu)
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*
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* Description: This causes a thread to be scheduled on every cpu,
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* each of which disables interrupts. The result is that noone is
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* holding a spinlock or inside any other preempt-disabled region when
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* @fn() runs.
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*
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* This can be thought of as a very heavy write lock, equivalent to
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* grabbing every spinlock in the kernel. */
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int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);
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/**
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* __stop_machine: freeze the machine on all CPUs and run this function
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* @fn: the function to run
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* @data: the data ptr for the @fn
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* @cpus: the cpus to run the @fn() on (NULL = any online cpu)
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*
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* Description: This is a special version of the above, which assumes cpus
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* won't come or go while it's being called. Used by hotplug cpu.
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*/
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int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);
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/**
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* stop_machine_create: create all stop_machine threads
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*
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* Description: This causes all stop_machine threads to be created before
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* stop_machine actually gets called. This can be used by subsystems that
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* need a non failing stop_machine infrastructure.
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*/
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int stop_machine_create(void);
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/**
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* stop_machine_destroy: destroy all stop_machine threads
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*
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* Description: This causes all stop_machine threads which were created with
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* stop_machine_create to be destroyed again.
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*/
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void stop_machine_destroy(void);
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#else
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static inline int stop_machine(int (*fn)(void *), void *data,
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const struct cpumask *cpus)
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{
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int ret;
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local_irq_disable();
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ret = fn(data);
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local_irq_enable();
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return ret;
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}
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static inline int stop_machine_create(void) { return 0; }
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static inline void stop_machine_destroy(void) { }
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#endif /* CONFIG_SMP */
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#endif /* _LINUX_STOP_MACHINE */
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