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![Peter Zijlstra](/assets/img/avatar_default.png)
Function-scope statics are discouraged because they are easily overlooked and can cause subtle bugs/races due to their global (non-SMP safe) nature. Linus noticed that we did this for sched_param - at minimum make the const. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: Message-ID: <AANLkTinotRxScOHEb0HgFgSpGPkq_6jKTv5CfvnQM=ee@mail.gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
424 lines
11 KiB
C
424 lines
11 KiB
C
/* Kernel thread helper functions.
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* Copyright (C) 2004 IBM Corporation, Rusty Russell.
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*
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* Creation is done via kthreadd, so that we get a clean environment
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* even if we're invoked from userspace (think modprobe, hotplug cpu,
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* etc.).
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*/
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#include <linux/sched.h>
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#include <linux/kthread.h>
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#include <linux/completion.h>
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#include <linux/err.h>
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#include <linux/cpuset.h>
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#include <linux/unistd.h>
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#include <linux/file.h>
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/slab.h>
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#include <linux/freezer.h>
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#include <trace/events/sched.h>
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static DEFINE_SPINLOCK(kthread_create_lock);
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static LIST_HEAD(kthread_create_list);
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struct task_struct *kthreadd_task;
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struct kthread_create_info
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{
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/* Information passed to kthread() from kthreadd. */
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int (*threadfn)(void *data);
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void *data;
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/* Result passed back to kthread_create() from kthreadd. */
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struct task_struct *result;
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struct completion done;
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struct list_head list;
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};
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struct kthread {
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int should_stop;
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void *data;
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struct completion exited;
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};
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#define to_kthread(tsk) \
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container_of((tsk)->vfork_done, struct kthread, exited)
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/**
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* kthread_should_stop - should this kthread return now?
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*
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* When someone calls kthread_stop() on your kthread, it will be woken
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* and this will return true. You should then return, and your return
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* value will be passed through to kthread_stop().
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*/
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int kthread_should_stop(void)
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{
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return to_kthread(current)->should_stop;
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}
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EXPORT_SYMBOL(kthread_should_stop);
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/**
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* kthread_data - return data value specified on kthread creation
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* @task: kthread task in question
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*
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* Return the data value specified when kthread @task was created.
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* The caller is responsible for ensuring the validity of @task when
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* calling this function.
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*/
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void *kthread_data(struct task_struct *task)
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{
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return to_kthread(task)->data;
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}
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static int kthread(void *_create)
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{
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/* Copy data: it's on kthread's stack */
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struct kthread_create_info *create = _create;
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int (*threadfn)(void *data) = create->threadfn;
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void *data = create->data;
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struct kthread self;
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int ret;
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self.should_stop = 0;
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self.data = data;
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init_completion(&self.exited);
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current->vfork_done = &self.exited;
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/* OK, tell user we're spawned, wait for stop or wakeup */
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__set_current_state(TASK_UNINTERRUPTIBLE);
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create->result = current;
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complete(&create->done);
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schedule();
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ret = -EINTR;
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if (!self.should_stop)
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ret = threadfn(data);
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/* we can't just return, we must preserve "self" on stack */
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do_exit(ret);
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}
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static void create_kthread(struct kthread_create_info *create)
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{
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int pid;
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/* We want our own signal handler (we take no signals by default). */
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pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
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if (pid < 0) {
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create->result = ERR_PTR(pid);
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complete(&create->done);
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}
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}
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/**
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* kthread_create - create a kthread.
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* @threadfn: the function to run until signal_pending(current).
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* @data: data ptr for @threadfn.
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* @namefmt: printf-style name for the thread.
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*
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* Description: This helper function creates and names a kernel
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* thread. The thread will be stopped: use wake_up_process() to start
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* it. See also kthread_run().
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*
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* When woken, the thread will run @threadfn() with @data as its
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* argument. @threadfn() can either call do_exit() directly if it is a
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* standalone thread for which noone will call kthread_stop(), or
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* return when 'kthread_should_stop()' is true (which means
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* kthread_stop() has been called). The return value should be zero
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* or a negative error number; it will be passed to kthread_stop().
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*
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* Returns a task_struct or ERR_PTR(-ENOMEM).
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*/
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struct task_struct *kthread_create(int (*threadfn)(void *data),
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void *data,
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const char namefmt[],
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...)
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{
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struct kthread_create_info create;
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create.threadfn = threadfn;
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create.data = data;
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init_completion(&create.done);
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spin_lock(&kthread_create_lock);
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list_add_tail(&create.list, &kthread_create_list);
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spin_unlock(&kthread_create_lock);
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wake_up_process(kthreadd_task);
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wait_for_completion(&create.done);
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if (!IS_ERR(create.result)) {
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static const struct sched_param param = { .sched_priority = 0 };
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va_list args;
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va_start(args, namefmt);
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vsnprintf(create.result->comm, sizeof(create.result->comm),
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namefmt, args);
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va_end(args);
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/*
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* root may have changed our (kthreadd's) priority or CPU mask.
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* The kernel thread should not inherit these properties.
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*/
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sched_setscheduler_nocheck(create.result, SCHED_NORMAL, ¶m);
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set_cpus_allowed_ptr(create.result, cpu_all_mask);
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}
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return create.result;
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}
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EXPORT_SYMBOL(kthread_create);
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/**
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* kthread_bind - bind a just-created kthread to a cpu.
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* @p: thread created by kthread_create().
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* @cpu: cpu (might not be online, must be possible) for @k to run on.
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*
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* Description: This function is equivalent to set_cpus_allowed(),
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* except that @cpu doesn't need to be online, and the thread must be
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* stopped (i.e., just returned from kthread_create()).
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*/
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void kthread_bind(struct task_struct *p, unsigned int cpu)
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{
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/* Must have done schedule() in kthread() before we set_task_cpu */
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if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) {
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WARN_ON(1);
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return;
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}
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p->cpus_allowed = cpumask_of_cpu(cpu);
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p->rt.nr_cpus_allowed = 1;
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p->flags |= PF_THREAD_BOUND;
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}
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EXPORT_SYMBOL(kthread_bind);
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/**
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* kthread_stop - stop a thread created by kthread_create().
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* @k: thread created by kthread_create().
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*
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* Sets kthread_should_stop() for @k to return true, wakes it, and
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* waits for it to exit. This can also be called after kthread_create()
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* instead of calling wake_up_process(): the thread will exit without
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* calling threadfn().
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*
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* If threadfn() may call do_exit() itself, the caller must ensure
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* task_struct can't go away.
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*
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* Returns the result of threadfn(), or %-EINTR if wake_up_process()
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* was never called.
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*/
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int kthread_stop(struct task_struct *k)
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{
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struct kthread *kthread;
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int ret;
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trace_sched_kthread_stop(k);
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get_task_struct(k);
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kthread = to_kthread(k);
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barrier(); /* it might have exited */
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if (k->vfork_done != NULL) {
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kthread->should_stop = 1;
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wake_up_process(k);
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wait_for_completion(&kthread->exited);
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}
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ret = k->exit_code;
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put_task_struct(k);
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trace_sched_kthread_stop_ret(ret);
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return ret;
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}
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EXPORT_SYMBOL(kthread_stop);
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int kthreadd(void *unused)
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{
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struct task_struct *tsk = current;
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/* Setup a clean context for our children to inherit. */
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set_task_comm(tsk, "kthreadd");
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ignore_signals(tsk);
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set_cpus_allowed_ptr(tsk, cpu_all_mask);
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set_mems_allowed(node_states[N_HIGH_MEMORY]);
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current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
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for (;;) {
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set_current_state(TASK_INTERRUPTIBLE);
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if (list_empty(&kthread_create_list))
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schedule();
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__set_current_state(TASK_RUNNING);
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spin_lock(&kthread_create_lock);
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while (!list_empty(&kthread_create_list)) {
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struct kthread_create_info *create;
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create = list_entry(kthread_create_list.next,
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struct kthread_create_info, list);
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list_del_init(&create->list);
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spin_unlock(&kthread_create_lock);
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create_kthread(create);
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spin_lock(&kthread_create_lock);
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}
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spin_unlock(&kthread_create_lock);
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}
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return 0;
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}
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void __init_kthread_worker(struct kthread_worker *worker,
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const char *name,
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struct lock_class_key *key)
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{
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spin_lock_init(&worker->lock);
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lockdep_set_class_and_name(&worker->lock, key, name);
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INIT_LIST_HEAD(&worker->work_list);
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worker->task = NULL;
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}
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EXPORT_SYMBOL_GPL(__init_kthread_worker);
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/**
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* kthread_worker_fn - kthread function to process kthread_worker
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* @worker_ptr: pointer to initialized kthread_worker
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*
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* This function can be used as @threadfn to kthread_create() or
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* kthread_run() with @worker_ptr argument pointing to an initialized
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* kthread_worker. The started kthread will process work_list until
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* the it is stopped with kthread_stop(). A kthread can also call
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* this function directly after extra initialization.
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*
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* Different kthreads can be used for the same kthread_worker as long
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* as there's only one kthread attached to it at any given time. A
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* kthread_worker without an attached kthread simply collects queued
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* kthread_works.
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*/
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int kthread_worker_fn(void *worker_ptr)
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{
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struct kthread_worker *worker = worker_ptr;
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struct kthread_work *work;
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WARN_ON(worker->task);
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worker->task = current;
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repeat:
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set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
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if (kthread_should_stop()) {
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__set_current_state(TASK_RUNNING);
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spin_lock_irq(&worker->lock);
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worker->task = NULL;
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spin_unlock_irq(&worker->lock);
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return 0;
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}
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work = NULL;
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spin_lock_irq(&worker->lock);
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if (!list_empty(&worker->work_list)) {
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work = list_first_entry(&worker->work_list,
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struct kthread_work, node);
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list_del_init(&work->node);
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}
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spin_unlock_irq(&worker->lock);
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if (work) {
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__set_current_state(TASK_RUNNING);
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work->func(work);
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smp_wmb(); /* wmb worker-b0 paired with flush-b1 */
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work->done_seq = work->queue_seq;
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smp_mb(); /* mb worker-b1 paired with flush-b0 */
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if (atomic_read(&work->flushing))
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wake_up_all(&work->done);
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} else if (!freezing(current))
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schedule();
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try_to_freeze();
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goto repeat;
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}
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EXPORT_SYMBOL_GPL(kthread_worker_fn);
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/**
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* queue_kthread_work - queue a kthread_work
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* @worker: target kthread_worker
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* @work: kthread_work to queue
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*
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* Queue @work to work processor @task for async execution. @task
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* must have been created with kthread_worker_create(). Returns %true
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* if @work was successfully queued, %false if it was already pending.
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*/
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bool queue_kthread_work(struct kthread_worker *worker,
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struct kthread_work *work)
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{
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bool ret = false;
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unsigned long flags;
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spin_lock_irqsave(&worker->lock, flags);
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if (list_empty(&work->node)) {
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list_add_tail(&work->node, &worker->work_list);
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work->queue_seq++;
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if (likely(worker->task))
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wake_up_process(worker->task);
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ret = true;
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}
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spin_unlock_irqrestore(&worker->lock, flags);
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return ret;
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}
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EXPORT_SYMBOL_GPL(queue_kthread_work);
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/**
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* flush_kthread_work - flush a kthread_work
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* @work: work to flush
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*
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* If @work is queued or executing, wait for it to finish execution.
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*/
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void flush_kthread_work(struct kthread_work *work)
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{
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int seq = work->queue_seq;
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atomic_inc(&work->flushing);
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/*
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* mb flush-b0 paired with worker-b1, to make sure either
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* worker sees the above increment or we see done_seq update.
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*/
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smp_mb__after_atomic_inc();
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/* A - B <= 0 tests whether B is in front of A regardless of overflow */
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wait_event(work->done, seq - work->done_seq <= 0);
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atomic_dec(&work->flushing);
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/*
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* rmb flush-b1 paired with worker-b0, to make sure our caller
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* sees every change made by work->func().
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*/
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smp_mb__after_atomic_dec();
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}
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EXPORT_SYMBOL_GPL(flush_kthread_work);
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struct kthread_flush_work {
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struct kthread_work work;
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struct completion done;
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};
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static void kthread_flush_work_fn(struct kthread_work *work)
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{
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struct kthread_flush_work *fwork =
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container_of(work, struct kthread_flush_work, work);
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complete(&fwork->done);
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}
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/**
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* flush_kthread_worker - flush all current works on a kthread_worker
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* @worker: worker to flush
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*
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* Wait until all currently executing or pending works on @worker are
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* finished.
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*/
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void flush_kthread_worker(struct kthread_worker *worker)
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{
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struct kthread_flush_work fwork = {
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KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
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COMPLETION_INITIALIZER_ONSTACK(fwork.done),
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};
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queue_kthread_work(worker, &fwork.work);
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wait_for_completion(&fwork.done);
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}
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EXPORT_SYMBOL_GPL(flush_kthread_worker);
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