// SPDX-License-Identifier: GPL-2.0-only/* * Copyright (C) 2021 Oracle Corporation */#include <linux/slab.h>#include <linux/completion.h>#include <linux/sched/task.h>#include <linux/sched/vhost_task.h>#include <linux/sched/signal.h> enum vhost_task_flags {	VHOST_TASK_FLAGS_STOP,}; struct vhost_task {	bool (*fn)(void *data);	void *data;	struct completion exited;	unsigned long flags;	struct task_struct *task;}; static int vhost_task_fn(void *data){	struct vhost_task *vtsk = data;	bool dead = false; 	for (;;) {		bool did_work; 		/* mb paired w/ vhost_task_stop */		if (test_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags))			break; 		if (!dead && signal_pending(current)) {			struct ksignal ksig;			/*			 * Calling get_signal will block in SIGSTOP,			 * or clear fatal_signal_pending, but remember			 * what was set.			 *			 * This thread won't actually exit until all			 * of the file descriptors are closed, and			 * the release function is called.			 */			dead = get_signal(&ksig);			if (dead)				clear_thread_flag(TIF_SIGPENDING);		} 		did_work = vtsk->fn(vtsk->data);		if (!did_work) {			set_current_state(TASK_INTERRUPTIBLE);			schedule();		}	} 	complete(&vtsk->exited);	do_exit(0);} /** * vhost_task_wake - wakeup the vhost_task * @vtsk: vhost_task to wake * * wake up the vhost_task worker thread */void vhost_task_wake(struct vhost_task *vtsk){	wake_up_process(vtsk->task);}EXPORT_SYMBOL_GPL(vhost_task_wake); /** * vhost_task_stop - stop a vhost_task * @vtsk: vhost_task to stop * * vhost_task_fn ensures the worker thread exits after * VHOST_TASK_FLAGS_SOP becomes true. */void vhost_task_stop(struct vhost_task *vtsk){	set_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags);	vhost_task_wake(vtsk);	/*	 * Make sure vhost_task_fn is no longer accessing the vhost_task before	 * freeing it below.	 */	wait_for_completion(&vtsk->exited);	kfree(vtsk);}EXPORT_SYMBOL_GPL(vhost_task_stop); /** * vhost_task_create - create a copy of a task to be used by the kernel * @fn: vhost worker function * @arg: data to be passed to fn * @name: the thread's name * * This returns a specialized task for use by the vhost layer or NULL on * failure. The returned task is inactive, and the caller must fire it up * through vhost_task_start(). */struct vhost_task *vhost_task_create(bool (*fn)(void *), void *arg,				     const char *name){	struct kernel_clone_args args = {		.flags		= CLONE_FS | CLONE_UNTRACED | CLONE_VM |				  CLONE_THREAD | CLONE_SIGHAND,		.exit_signal	= 0,		.fn		= vhost_task_fn,		.name		= name,		.user_worker	= 1,		.no_files	= 1,	};	struct vhost_task *vtsk;	struct task_struct *tsk; 	vtsk = kzalloc(sizeof(*vtsk), GFP_KERNEL);	if (!vtsk)		return NULL;	init_completion(&vtsk->exited);	vtsk->data = arg;	vtsk->fn = fn; 	args.fn_arg = vtsk; 	tsk = copy_process(NULL, 0, NUMA_NO_NODE, &args);	if (IS_ERR(tsk)) {		kfree(vtsk);		return NULL;	} 	vtsk->task = tsk;	return vtsk;}EXPORT_SYMBOL_GPL(vhost_task_create); /** * vhost_task_start - start a vhost_task created with vhost_task_create * @vtsk: vhost_task to wake up */void vhost_task_start(struct vhost_task *vtsk){	wake_up_new_task(vtsk->task);}EXPORT_SYMBOL_GPL(vhost_task_start);