stop_machine.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _LINUX_STOP_MACHINE
  3#define _LINUX_STOP_MACHINE
  4
  5#include <linux/cpu.h>
  6#include <linux/cpumask_types.h>
  7#include <linux/smp.h>
  8#include <linux/list.h>
  9
 10/*
 11 * stop_cpu[s]() is simplistic per-cpu maximum priority cpu
 12 * monopolization mechanism.  The caller can specify a non-sleeping
 13 * function to be executed on a single or multiple cpus preempting all
 14 * other processes and monopolizing those cpus until it finishes.
 15 *
 16 * Resources for this mechanism are preallocated when a cpu is brought
 17 * up and requests are guaranteed to be served as long as the target
 18 * cpus are online.
 19 */
 20typedef int (*cpu_stop_fn_t)(void *arg);
 21
 22#ifdef CONFIG_SMP
 23
 24struct cpu_stop_work {
 25	struct list_head	list;		/* cpu_stopper->works */
 26	cpu_stop_fn_t		fn;
 27	unsigned long		caller;
 28	void			*arg;
 29	struct cpu_stop_done	*done;
 30};
 31
 32int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
 33int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
 34bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
 35			 struct cpu_stop_work *work_buf);
 36void stop_machine_park(int cpu);
 37void stop_machine_unpark(int cpu);
 38void stop_machine_yield(const struct cpumask *cpumask);
 39
 40extern void print_stop_info(const char *log_lvl, struct task_struct *task);
 41
 42#else	/* CONFIG_SMP */
 43
 44#include <linux/workqueue.h>
 45
 46struct cpu_stop_work {
 47	struct work_struct	work;
 48	cpu_stop_fn_t		fn;
 49	void			*arg;
 50};
 51
 52static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
 53{
 54	int ret = -ENOENT;
 55	preempt_disable();
 56	if (cpu == smp_processor_id())
 57		ret = fn(arg);
 58	preempt_enable();
 59	return ret;
 60}
 61
 62static void stop_one_cpu_nowait_workfn(struct work_struct *work)
 63{
 64	struct cpu_stop_work *stwork =
 65		container_of(work, struct cpu_stop_work, work);
 66	preempt_disable();
 67	stwork->fn(stwork->arg);
 68	preempt_enable();
 69}
 70
 71static inline bool stop_one_cpu_nowait(unsigned int cpu,
 72				       cpu_stop_fn_t fn, void *arg,
 73				       struct cpu_stop_work *work_buf)
 74{
 75	if (cpu == smp_processor_id()) {
 76		INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
 77		work_buf->fn = fn;
 78		work_buf->arg = arg;
 79		schedule_work(&work_buf->work);
 80		return true;
 81	}
 82
 83	return false;
 84}
 85
 86static inline void print_stop_info(const char *log_lvl, struct task_struct *task) { }
 87
 88#endif	/* CONFIG_SMP */
 89
 90/*
 91 * stop_machine "Bogolock": stop the entire machine, disable interrupts.
 92 * This is a very heavy lock, which is equivalent to grabbing every raw
 93 * spinlock (and more).  So the "read" side to such a lock is anything
 94 * which disables preemption.
 95 */
 96#if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
 97
 98/**
 99 * stop_machine: freeze the machine on all CPUs and run this function
100 * @fn: the function to run
101 * @data: the data ptr to pass to @fn()
102 * @cpus: the cpus to run @fn() on (NULL = run on each online CPU)
103 *
104 * Description: This causes a thread to be scheduled on every CPU, which
105 * will run with interrupts disabled.  Each CPU specified by @cpus will
106 * run @fn.  While @fn is executing, there will no other CPUs holding
107 * a raw spinlock or running within any other type of preempt-disabled
108 * region of code.
109 *
110 * When @cpus specifies only a single CPU, this can be thought of as
111 * a reader-writer lock where readers disable preemption (for example,
112 * by holding a raw spinlock) and where the insanely heavy writers run
113 * @fn while also preventing any other CPU from doing any useful work.
114 * These writers can also be thought of as having implicitly grabbed every
115 * raw spinlock in the kernel.
116 *
117 * When @fn is a no-op, this can be thought of as an RCU implementation
118 * where readers again disable preemption and writers use stop_machine()
119 * in place of synchronize_rcu(), albeit with orders of magnitude more
120 * disruption than even that of synchronize_rcu_expedited().
121 *
122 * Although only one stop_machine() operation can proceed at a time,
123 * the possibility of blocking in cpus_read_lock() means that the caller
124 * cannot usefully rely on this serialization.
125 *
126 * Return: 0 if all invocations of @fn return zero.  Otherwise, the
127 * value returned by an arbitrarily chosen member of the set of calls to
128 * @fn that returned non-zero.
129 */
130int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
131
132/**
133 * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
134 * @fn: the function to run
135 * @data: the data ptr to pass to @fn()
136 * @cpus: the cpus to run @fn() on (NULL = run on each online CPU)
137 *
138 * Same as above.  Avoids nested calls to cpus_read_lock().
139 *
140 * Context: Must be called from within a cpus_read_lock() protected region.
141 */
142int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
143
144/**
145 * stop_core_cpuslocked: - stop all threads on just one core
146 * @cpu: any cpu in the targeted core
147 * @fn: the function to run on each CPU in the core containing @cpu
148 * @data: the data ptr to pass to @fn()
149 *
150 * Same as above, but instead of every CPU, only the logical CPUs of the
151 * single core containing @cpu are affected.
152 *
153 * Context: Must be called from within a cpus_read_lock() protected region.
154 *
155 * Return: 0 if all invocations of @fn return zero.  Otherwise, the
156 * value returned by an arbitrarily chosen member of the set of calls to
157 * @fn that returned non-zero.
158 */
159int stop_core_cpuslocked(unsigned int cpu, cpu_stop_fn_t fn, void *data);
160
161int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
162				   const struct cpumask *cpus);
163#else	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
164
165static __always_inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
166					  const struct cpumask *cpus)
167{
168	unsigned long flags;
169	int ret;
170	local_irq_save(flags);
171	ret = fn(data);
172	local_irq_restore(flags);
173	return ret;
174}
175
176static __always_inline int
177stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
178{
179	return stop_machine_cpuslocked(fn, data, cpus);
180}
181
182static __always_inline int
183stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
184			       const struct cpumask *cpus)
185{
186	return stop_machine(fn, data, cpus);
187}
188
189#endif	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
190#endif	/* _LINUX_STOP_MACHINE */