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kernel/kthread.c
18.6 KB
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/* Kernel thread helper functions. * Copyright (C) 2004 IBM Corporation, Rusty Russell. * |
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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, * etc.). */ #include <linux/sched.h> #include <linux/kthread.h> #include <linux/completion.h> #include <linux/err.h> |
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#include <linux/cpuset.h> |
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#include <linux/unistd.h> #include <linux/file.h> |
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#include <linux/export.h> |
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#include <linux/mutex.h> |
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#include <linux/slab.h> #include <linux/freezer.h> |
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#include <linux/ptrace.h> |
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#include <linux/uaccess.h> |
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#include <trace/events/sched.h> |
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static DEFINE_SPINLOCK(kthread_create_lock); static LIST_HEAD(kthread_create_list); struct task_struct *kthreadd_task; |
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struct kthread_create_info { |
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/* Information passed to kthread() from kthreadd. */ |
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int (*threadfn)(void *data); void *data; |
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int node; |
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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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unsigned long flags; unsigned int cpu; |
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void *data; |
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struct completion parked; |
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struct completion exited; |
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}; |
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enum KTHREAD_BITS { KTHREAD_IS_PER_CPU = 0, KTHREAD_SHOULD_STOP, KTHREAD_SHOULD_PARK, KTHREAD_IS_PARKED, }; |
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#define __to_kthread(vfork) \ container_of(vfork, struct kthread, exited) static inline struct kthread *to_kthread(struct task_struct *k) { return __to_kthread(k->vfork_done); } static struct kthread *to_live_kthread(struct task_struct *k) { struct completion *vfork = ACCESS_ONCE(k->vfork_done); if (likely(vfork)) return __to_kthread(vfork); return NULL; } |
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/** * kthread_should_stop - should this kthread return now? * |
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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 * value will be passed through to kthread_stop(). */ |
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bool kthread_should_stop(void) |
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{ |
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return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags); |
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} EXPORT_SYMBOL(kthread_should_stop); |
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/** |
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* kthread_should_park - should this kthread park now? * * When someone calls kthread_park() on your kthread, it will be woken * and this will return true. You should then do the necessary * cleanup and call kthread_parkme() * * Similar to kthread_should_stop(), but this keeps the thread alive * and in a park position. kthread_unpark() "restarts" the thread and * calls the thread function again. */ bool kthread_should_park(void) { return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags); } /** |
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* kthread_freezable_should_stop - should this freezable kthread return now? * @was_frozen: optional out parameter, indicates whether %current was frozen * * kthread_should_stop() for freezable kthreads, which will enter * refrigerator if necessary. This function is safe from kthread_stop() / * freezer deadlock and freezable kthreads should use this function instead * of calling try_to_freeze() directly. */ bool kthread_freezable_should_stop(bool *was_frozen) { bool frozen = false; might_sleep(); if (unlikely(freezing(current))) frozen = __refrigerator(true); if (was_frozen) *was_frozen = frozen; return kthread_should_stop(); } EXPORT_SYMBOL_GPL(kthread_freezable_should_stop); /** |
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* kthread_data - return data value specified on kthread creation * @task: kthread task in question * * Return the data value specified when kthread @task was created. * The caller is responsible for ensuring the validity of @task when * calling this function. */ void *kthread_data(struct task_struct *task) { return to_kthread(task)->data; } |
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/** * probe_kthread_data - speculative version of kthread_data() * @task: possible kthread task in question * * @task could be a kthread task. Return the data value specified when it * was created if accessible. If @task isn't a kthread task or its data is * inaccessible for any reason, %NULL is returned. This function requires * that @task itself is safe to dereference. */ void *probe_kthread_data(struct task_struct *task) { struct kthread *kthread = to_kthread(task); void *data = NULL; probe_kernel_read(&data, &kthread->data, sizeof(data)); return data; } |
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static void __kthread_parkme(struct kthread *self) { |
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__set_current_state(TASK_PARKED); |
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while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) { if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags)) complete(&self->parked); schedule(); |
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__set_current_state(TASK_PARKED); |
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} clear_bit(KTHREAD_IS_PARKED, &self->flags); __set_current_state(TASK_RUNNING); } void kthread_parkme(void) { __kthread_parkme(to_kthread(current)); } |
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static int kthread(void *_create) { |
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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; void *data = create->data; |
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struct completion *done; |
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struct kthread self; int ret; |
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self.flags = 0; |
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self.data = data; |
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init_completion(&self.exited); |
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init_completion(&self.parked); |
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current->vfork_done = &self.exited; |
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/* If user was SIGKILLed, I release the structure. */ done = xchg(&create->done, NULL); if (!done) { kfree(create); do_exit(-EINTR); } |
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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(done); |
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schedule(); |
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ret = -EINTR; |
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if (!test_bit(KTHREAD_SHOULD_STOP, &self.flags)) { __kthread_parkme(&self); ret = threadfn(data); } |
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/* we can't just return, we must preserve "self" on stack */ do_exit(ret); |
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} |
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/* called from do_fork() to get node information for about to be created task */ int tsk_fork_get_node(struct task_struct *tsk) { #ifdef CONFIG_NUMA if (tsk == kthreadd_task) return tsk->pref_node_fork; #endif return numa_node_id(); } |
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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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#ifdef CONFIG_NUMA current->pref_node_fork = create->node; #endif |
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/* We want our own signal handler (we take no signals by default). */ pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD); |
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if (pid < 0) { |
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/* If user was SIGKILLed, I release the structure. */ struct completion *done = xchg(&create->done, NULL); if (!done) { kfree(create); return; } |
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create->result = ERR_PTR(pid); |
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complete(done); |
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} |
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} |
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/** |
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* kthread_create_on_node - create a kthread. |
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* @threadfn: the function to run until signal_pending(current). * @data: data ptr for @threadfn. |
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* @node: memory node number. |
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* @namefmt: printf-style name for the thread. * * Description: This helper function creates and names a kernel * 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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* If thread is going to be bound on a particular cpu, give its node * in @node, to get NUMA affinity for kthread stack, or else give -1. |
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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 no one will call kthread_stop(), or |
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* return when 'kthread_should_stop()' is true (which means * kthread_stop() has been called). The return value should be zero * or a negative error number; it will be passed to kthread_stop(). * |
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* Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR). |
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*/ |
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struct task_struct *kthread_create_on_node(int (*threadfn)(void *data), |
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void *data, int node, |
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const char namefmt[], ...) |
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{ |
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DECLARE_COMPLETION_ONSTACK(done); struct task_struct *task; struct kthread_create_info *create = kmalloc(sizeof(*create), GFP_KERNEL); if (!create) return ERR_PTR(-ENOMEM); create->threadfn = threadfn; create->data = data; create->node = node; create->done = &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 in killable state, for I might be chosen by * the OOM killer while kthreadd is trying to allocate memory for * new kernel thread. */ if (unlikely(wait_for_completion_killable(&done))) { /* * If I was SIGKILLed before kthreadd (or new kernel thread) * calls complete(), leave the cleanup of this structure to * that thread. */ if (xchg(&create->done, NULL)) |
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return ERR_PTR(-EINTR); |
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/* * kthreadd (or new kernel thread) will call complete() * shortly. */ wait_for_completion(&done); } task = create->result; if (!IS_ERR(task)) { |
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static const struct sched_param param = { .sched_priority = 0 }; |
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va_list args; |
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|
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va_start(args, namefmt); |
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vsnprintf(task->comm, sizeof(task->comm), namefmt, args); |
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va_end(args); |
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/* * root may have changed our (kthreadd's) priority or CPU mask. * The kernel thread should not inherit these properties. */ |
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sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m); set_cpus_allowed_ptr(task, cpu_all_mask); |
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} |
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kfree(create); return task; |
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} |
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EXPORT_SYMBOL(kthread_create_on_node); |
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static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state) |
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{ |
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/* Must have done schedule() in kthread() before we set_task_cpu */ if (!wait_task_inactive(p, state)) { WARN_ON(1); return; } |
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/* It's safe because the task is inactive. */ do_set_cpus_allowed(p, cpumask_of(cpu)); |
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p->flags |= PF_NO_SETAFFINITY; |
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} |
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/** |
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* kthread_bind - bind a just-created kthread to a cpu. * @p: thread created by kthread_create(). * @cpu: cpu (might not be online, must be possible) for @k to run on. * * Description: This function is equivalent to set_cpus_allowed(), * except that @cpu doesn't need to be online, and the thread must be * stopped (i.e., just returned from kthread_create()). */ void kthread_bind(struct task_struct *p, unsigned int cpu) { |
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__kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE); |
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} EXPORT_SYMBOL(kthread_bind); /** |
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* kthread_create_on_cpu - Create a cpu bound kthread * @threadfn: the function to run until signal_pending(current). * @data: data ptr for @threadfn. * @cpu: The cpu on which the thread should be bound, * @namefmt: printf-style name for the thread. Format is restricted * to "name.*%u". Code fills in cpu number. * * Description: This helper function creates and names a kernel thread * The thread will be woken and put into park mode. */ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data), void *data, unsigned int cpu, const char *namefmt) { struct task_struct *p; p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt, cpu); if (IS_ERR(p)) return p; set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags); to_kthread(p)->cpu = cpu; /* Park the thread to get it out of TASK_UNINTERRUPTIBLE state */ kthread_park(p); return p; } |
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static void __kthread_unpark(struct task_struct *k, struct kthread *kthread) { clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags); /* * We clear the IS_PARKED bit here as we don't wait * until the task has left the park code. So if we'd * park before that happens we'd see the IS_PARKED bit * which might be about to be cleared. */ if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) { if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags)) __kthread_bind(k, kthread->cpu, TASK_PARKED); wake_up_state(k, TASK_PARKED); } } |
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/** * kthread_unpark - unpark a thread created by kthread_create(). * @k: thread created by kthread_create(). * * Sets kthread_should_park() for @k to return false, wakes it, and * waits for it to return. If the thread is marked percpu then its * bound to the cpu again. */ void kthread_unpark(struct task_struct *k) { |
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struct kthread *kthread = to_live_kthread(k); |
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if (kthread) __kthread_unpark(k, kthread); |
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} /** * kthread_park - park a thread created by kthread_create(). * @k: thread created by kthread_create(). * * Sets kthread_should_park() for @k to return true, wakes it, and * waits for it to return. This can also be called after kthread_create() * instead of calling wake_up_process(): the thread will park without * calling threadfn(). * * Returns 0 if the thread is parked, -ENOSYS if the thread exited. * If called by the kthread itself just the park bit is set. */ int kthread_park(struct task_struct *k) { |
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struct kthread *kthread = to_live_kthread(k); |
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int ret = -ENOSYS; if (kthread) { if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) { set_bit(KTHREAD_SHOULD_PARK, &kthread->flags); if (k != current) { wake_up_process(k); wait_for_completion(&kthread->parked); } } ret = 0; } |
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return ret; } /** |
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* kthread_stop - stop a thread created by kthread_create(). * @k: thread created by kthread_create(). * * 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() * instead of calling wake_up_process(): the thread will exit without * calling threadfn(). * * If threadfn() may call do_exit() itself, the caller must ensure * task_struct can't go away. |
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* * Returns the result of threadfn(), or %-EINTR if wake_up_process() * was never called. */ |
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int kthread_stop(struct task_struct *k) { |
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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); kthread = to_live_kthread(k); |
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if (kthread) { set_bit(KTHREAD_SHOULD_STOP, &kthread->flags); |
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__kthread_unpark(k, kthread); |
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wake_up_process(k); wait_for_completion(&kthread->exited); } ret = k->exit_code; |
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put_task_struct(k); |
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|
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trace_sched_kthread_stop_ret(ret); |
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return ret; } |
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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); |
1a2142afa cpumask: remove d... |
473 |
set_cpus_allowed_ptr(tsk, cpu_all_mask); |
aee4faa49 kthread: use N_ME... |
474 |
set_mems_allowed(node_states[N_MEMORY]); |
73c279927 kthread: don't de... |
475 |
|
34b087e48 freezer: kill unu... |
476 |
current->flags |= PF_NOFREEZE; |
73c279927 kthread: don't de... |
477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 |
for (;;) { set_current_state(TASK_INTERRUPTIBLE); if (list_empty(&kthread_create_list)) schedule(); __set_current_state(TASK_RUNNING); spin_lock(&kthread_create_lock); while (!list_empty(&kthread_create_list)) { struct kthread_create_info *create; create = list_entry(kthread_create_list.next, struct kthread_create_info, list); list_del_init(&create->list); spin_unlock(&kthread_create_lock); create_kthread(create); spin_lock(&kthread_create_lock); } spin_unlock(&kthread_create_lock); } return 0; } |
b56c0d893 kthread: implemen... |
502 |
|
4f32e9b1f kthread_work: mak... |
503 504 505 506 507 508 509 510 511 512 |
void __init_kthread_worker(struct kthread_worker *worker, const char *name, struct lock_class_key *key) { spin_lock_init(&worker->lock); lockdep_set_class_and_name(&worker->lock, key, name); INIT_LIST_HEAD(&worker->work_list); worker->task = NULL; } EXPORT_SYMBOL_GPL(__init_kthread_worker); |
b56c0d893 kthread: implemen... |
513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 |
/** * kthread_worker_fn - kthread function to process kthread_worker * @worker_ptr: pointer to initialized kthread_worker * * This function can be used as @threadfn to kthread_create() or * kthread_run() with @worker_ptr argument pointing to an initialized * kthread_worker. The started kthread will process work_list until * the it is stopped with kthread_stop(). A kthread can also call * this function directly after extra initialization. * * Different kthreads can be used for the same kthread_worker as long * as there's only one kthread attached to it at any given time. A * kthread_worker without an attached kthread simply collects queued * kthread_works. */ int kthread_worker_fn(void *worker_ptr) { struct kthread_worker *worker = worker_ptr; struct kthread_work *work; WARN_ON(worker->task); worker->task = current; repeat: set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */ if (kthread_should_stop()) { __set_current_state(TASK_RUNNING); spin_lock_irq(&worker->lock); worker->task = NULL; spin_unlock_irq(&worker->lock); return 0; } work = NULL; spin_lock_irq(&worker->lock); if (!list_empty(&worker->work_list)) { work = list_first_entry(&worker->work_list, struct kthread_work, node); list_del_init(&work->node); } |
46f3d9762 kthread_worker: r... |
553 |
worker->current_work = work; |
b56c0d893 kthread: implemen... |
554 555 556 557 558 |
spin_unlock_irq(&worker->lock); if (work) { __set_current_state(TASK_RUNNING); work->func(work); |
b56c0d893 kthread: implemen... |
559 560 561 562 563 564 565 |
} else if (!freezing(current)) schedule(); try_to_freeze(); goto repeat; } EXPORT_SYMBOL_GPL(kthread_worker_fn); |
9a2e03d8e kthread_worker: r... |
566 567 568 569 570 571 572 573 |
/* insert @work before @pos in @worker */ static void insert_kthread_work(struct kthread_worker *worker, struct kthread_work *work, struct list_head *pos) { lockdep_assert_held(&worker->lock); list_add_tail(&work->node, pos); |
46f3d9762 kthread_worker: r... |
574 |
work->worker = worker; |
9a2e03d8e kthread_worker: r... |
575 576 577 |
if (likely(worker->task)) wake_up_process(worker->task); } |
b56c0d893 kthread: implemen... |
578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 |
/** * queue_kthread_work - queue a kthread_work * @worker: target kthread_worker * @work: kthread_work to queue * * Queue @work to work processor @task for async execution. @task * must have been created with kthread_worker_create(). Returns %true * if @work was successfully queued, %false if it was already pending. */ bool queue_kthread_work(struct kthread_worker *worker, struct kthread_work *work) { bool ret = false; unsigned long flags; spin_lock_irqsave(&worker->lock, flags); if (list_empty(&work->node)) { |
9a2e03d8e kthread_worker: r... |
595 |
insert_kthread_work(worker, work, &worker->work_list); |
b56c0d893 kthread: implemen... |
596 597 598 599 600 601 |
ret = true; } spin_unlock_irqrestore(&worker->lock, flags); return ret; } EXPORT_SYMBOL_GPL(queue_kthread_work); |
9a2e03d8e kthread_worker: r... |
602 603 604 605 606 607 608 609 610 611 612 |
struct kthread_flush_work { struct kthread_work work; struct completion done; }; static void kthread_flush_work_fn(struct kthread_work *work) { struct kthread_flush_work *fwork = container_of(work, struct kthread_flush_work, work); complete(&fwork->done); } |
b56c0d893 kthread: implemen... |
613 614 615 616 617 618 619 620 |
/** * flush_kthread_work - flush a kthread_work * @work: work to flush * * If @work is queued or executing, wait for it to finish execution. */ void flush_kthread_work(struct kthread_work *work) { |
46f3d9762 kthread_worker: r... |
621 622 623 624 625 626 627 628 629 630 631 |
struct kthread_flush_work fwork = { KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn), COMPLETION_INITIALIZER_ONSTACK(fwork.done), }; struct kthread_worker *worker; bool noop = false; retry: worker = work->worker; if (!worker) return; |
b56c0d893 kthread: implemen... |
632 |
|
46f3d9762 kthread_worker: r... |
633 634 635 636 637 |
spin_lock_irq(&worker->lock); if (work->worker != worker) { spin_unlock_irq(&worker->lock); goto retry; } |
b56c0d893 kthread: implemen... |
638 |
|
46f3d9762 kthread_worker: r... |
639 640 641 642 643 644 |
if (!list_empty(&work->node)) insert_kthread_work(worker, &fwork.work, work->node.next); else if (worker->current_work == work) insert_kthread_work(worker, &fwork.work, worker->work_list.next); else noop = true; |
b56c0d893 kthread: implemen... |
645 |
|
46f3d9762 kthread_worker: r... |
646 |
spin_unlock_irq(&worker->lock); |
b56c0d893 kthread: implemen... |
647 |
|
46f3d9762 kthread_worker: r... |
648 649 |
if (!noop) wait_for_completion(&fwork.done); |
b56c0d893 kthread: implemen... |
650 651 |
} EXPORT_SYMBOL_GPL(flush_kthread_work); |
b56c0d893 kthread: implemen... |
652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 |
/** * flush_kthread_worker - flush all current works on a kthread_worker * @worker: worker to flush * * Wait until all currently executing or pending works on @worker are * finished. */ void flush_kthread_worker(struct kthread_worker *worker) { struct kthread_flush_work fwork = { KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn), COMPLETION_INITIALIZER_ONSTACK(fwork.done), }; queue_kthread_work(worker, &fwork.work); wait_for_completion(&fwork.done); } EXPORT_SYMBOL_GPL(flush_kthread_worker); |