Line data    Source code

       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.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             :  */
      20             : typedef int (*cpu_stop_fn_t)(void *arg);
      21             : 
      22             : #ifdef CONFIG_SMP
      23             : 
      24             : struct 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             : 
      32             : int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
      33             : int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
      34             : bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
      35             :                          struct cpu_stop_work *work_buf);
      36             : void stop_machine_park(int cpu);
      37             : void stop_machine_unpark(int cpu);
      38             : void stop_machine_yield(const struct cpumask *cpumask);
      39             : 
      40             : extern void print_stop_info(const char *log_lvl, struct task_struct *task);
      41             : 
      42             : #else   /* CONFIG_SMP */
      43             : 
      44             : #include <linux/workqueue.h>
      45             : 
      46             : struct cpu_stop_work {
      47             :         struct work_struct      work;
      48             :         cpu_stop_fn_t           fn;
      49             :         void                    *arg;
      50             : };
      51             : 
      52             : static 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             : 
      62             : static 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             : 
      71             : static 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             : 
      86             : static 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
      92             :  * interrupts.  This is a very heavy lock, which is equivalent to
      93             :  * grabbing every spinlock (and more).  So the "read" side to such a
      94             :  * lock is anything 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 for the @fn()
     102             :  * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
     103             :  *
     104             :  * Description: This causes a thread to be scheduled on every cpu,
     105             :  * each of which disables interrupts.  The result is that no one is
     106             :  * holding a spinlock or inside any other preempt-disabled region when
     107             :  * @fn() runs.
     108             :  *
     109             :  * This can be thought of as a very heavy write lock, equivalent to
     110             :  * grabbing every spinlock in the kernel.
     111             :  *
     112             :  * Protects against CPU hotplug.
     113             :  */
     114             : int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
     115             : 
     116             : /**
     117             :  * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
     118             :  * @fn: the function to run
     119             :  * @data: the data ptr for the @fn()
     120             :  * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
     121             :  *
     122             :  * Same as above. Must be called from with in a cpus_read_lock() protected
     123             :  * region. Avoids nested calls to cpus_read_lock().
     124             :  */
     125             : int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
     126             : 
     127             : int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
     128             :                                    const struct cpumask *cpus);
     129             : #else   /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
     130             : 
     131             : static __always_inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
     132             :                                           const struct cpumask *cpus)
     133             : {
     134             :         unsigned long flags;
     135             :         int ret;
     136           1 :         local_irq_save(flags);
     137           1 :         ret = fn(data);
     138           1 :         local_irq_restore(flags);
     139             :         return ret;
     140             : }
     141             : 
     142             : static __always_inline int
     143             : stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
     144             : {
     145           1 :         return stop_machine_cpuslocked(fn, data, cpus);
     146             : }
     147             : 
     148             : static __always_inline int
     149             : stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
     150             :                                const struct cpumask *cpus)
     151             : {
     152             :         return stop_machine(fn, data, cpus);
     153             : }
     154             : 
     155             : #endif  /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
     156             : #endif  /* _LINUX_STOP_MACHINE */