kthread: Implement park/unpark facility (2a1d4460) · Commits · 戴 / test

include/linux/kthread.h

+10 −1

Original line number	Diff line number	Diff line
		@@ -14,6 +14,11 @@ struct task_struct kthread_create_on_node(int (threadfn)(void *data),
		kthread_create_on_node(threadfn, data, -1, namefmt, ##arg)


		struct task_struct kthread_create_on_cpu(int (threadfn)(void *data),
		void *data,
		unsigned int cpu,
		const char *namefmt);

		/**
		* kthread_run - create and wake a thread.
		* @threadfn: the function to run until signal_pending(current).
		@@ -34,9 +39,13 @@ struct task_struct kthread_create_on_node(int (threadfn)(void *data),

		void kthread_bind(struct task_struct *k, unsigned int cpu);
		int kthread_stop(struct task_struct *k);
		int kthread_should_stop(void);
		bool kthread_should_stop(void);
		bool kthread_should_park(void);
		bool kthread_freezable_should_stop(bool *was_frozen);
		void kthread_data(struct task_struct k);
		int kthread_park(struct task_struct *k);
		void kthread_unpark(struct task_struct *k);
		void kthread_parkme(void);

		int kthreadd(void *unused);
		extern struct task_struct *kthreadd_task;

kernel/kthread.c

+166 −19

Original line number	Diff line number	Diff line
		@@ -37,11 +37,20 @@ struct kthread_create_info
		};

		struct kthread {
		int should_stop;
		unsigned long flags;
		unsigned int cpu;
		void *data;
		struct completion parked;
		struct completion exited;
		};

		enum KTHREAD_BITS {
		KTHREAD_IS_PER_CPU = 0,
		KTHREAD_SHOULD_STOP,
		KTHREAD_SHOULD_PARK,
		KTHREAD_IS_PARKED,
		};

		#define to_kthread(tsk) \
		container_of((tsk)->vfork_done, struct kthread, exited)

		@@ -52,12 +61,28 @@ struct kthread {
		* and this will return true. You should then return, and your return
		* value will be passed through to kthread_stop().
		*/
		int kthread_should_stop(void)
		bool kthread_should_stop(void)
		{
		return to_kthread(current)->should_stop;
		return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
		}
		EXPORT_SYMBOL(kthread_should_stop);

		/**
		* 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);
		}

		/**
		* kthread_freezable_should_stop - should this freezable kthread return now?
		* @was_frozen: optional out parameter, indicates whether %current was frozen
		@@ -96,6 +121,24 @@ void kthread_data(struct task_struct task)
		return to_kthread(task)->data;
		}

		static void __kthread_parkme(struct kthread *self)
		{
		__set_current_state(TASK_INTERRUPTIBLE);
		while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) {
		if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
		complete(&self->parked);
		schedule();
		__set_current_state(TASK_INTERRUPTIBLE);
		}
		clear_bit(KTHREAD_IS_PARKED, &self->flags);
		__set_current_state(TASK_RUNNING);
		}

		void kthread_parkme(void)
		{
		__kthread_parkme(to_kthread(current));
		}

		static int kthread(void *_create)
		{
		/* Copy data: it's on kthread's stack */
		@@ -105,9 +148,10 @@ static int kthread(void *_create)
		struct kthread self;
		int ret;

		self.should_stop = 0;
		self.flags = 0;
		self.data = data;
		init_completion(&self.exited);
		init_completion(&self.parked);
		current->vfork_done = &self.exited;

		/* OK, tell user we're spawned, wait for stop or wakeup */
		@@ -117,9 +161,11 @@ static int kthread(void *_create)
		schedule();

		ret = -EINTR;
		if (!self.should_stop)
		ret = threadfn(data);

		if (!test_bit(KTHREAD_SHOULD_STOP, &self.flags)) {
		__kthread_parkme(&self);
		ret = threadfn(data);
		}
		/* we can't just return, we must preserve "self" on stack */
		do_exit(ret);
		}
		@@ -172,8 +218,7 @@ static void create_kthread(struct kthread_create_info *create)
		* Returns a task_struct or ERR_PTR(-ENOMEM).
		*/
		struct task_struct kthread_create_on_node(int (threadfn)(void *data),
		void *data,
		int node,
		void *data, int node,
		const char namefmt[],
		...)
		{
		@@ -210,6 +255,13 @@ struct task_struct kthread_create_on_node(int (threadfn)(void *data),
		}
		EXPORT_SYMBOL(kthread_create_on_node);

		static void __kthread_bind(struct task_struct *p, unsigned int cpu)
		{
		/* It's safe because the task is inactive. */
		do_set_cpus_allowed(p, cpumask_of(cpu));
		p->flags \|= PF_THREAD_BOUND;
		}

		/**
		* kthread_bind - bind a just-created kthread to a cpu.
		* @p: thread created by kthread_create().
		@@ -226,13 +278,111 @@ void kthread_bind(struct task_struct *p, unsigned int cpu)
		WARN_ON(1);
		return;
		}

		/* It's safe because the task is inactive. */
		do_set_cpus_allowed(p, cpumask_of(cpu));
		p->flags \|= PF_THREAD_BOUND;
		__kthread_bind(p, cpu);
		}
		EXPORT_SYMBOL(kthread_bind);

		/**
		* 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;
		}

		static struct kthread task_get_live_kthread(struct task_struct k)
		{
		struct kthread *kthread;

		get_task_struct(k);
		kthread = to_kthread(k);
		/* It might have exited */
		barrier();
		if (k->vfork_done != NULL)
		return kthread;
		return NULL;
		}

		/**
		* 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)
		{
		struct kthread *kthread = task_get_live_kthread(k);

		if (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);
		wake_up_process(k);
		}
		}
		put_task_struct(k);
		}

		/**
		* 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)
		{
		struct kthread *kthread = task_get_live_kthread(k);
		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;
		}
		put_task_struct(k);
		return ret;
		}

		/**
		* kthread_stop - stop a thread created by kthread_create().
		* @k: thread created by kthread_create().
		@@ -250,16 +400,13 @@ EXPORT_SYMBOL(kthread_bind);
		*/
		int kthread_stop(struct task_struct *k)
		{
		struct kthread *kthread;
		struct kthread *kthread = task_get_live_kthread(k);
		int ret;

		trace_sched_kthread_stop(k);
		get_task_struct(k);

		kthread = to_kthread(k);
		barrier(); /* it might have exited */
		if (k->vfork_done != NULL) {
		kthread->should_stop = 1;
		if (kthread) {
		set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
		clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
		wake_up_process(k);
		wait_for_completion(&kthread->exited);
		}

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