// SPDX-License-Identifier: GPL-2.0/* * Asynchronous refcounty things * * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com> * Copyright 2012 Google, Inc. */ #include <linux/closure.h>#include <linux/debugfs.h>#include <linux/export.h>#include <linux/rcupdate.h>#include <linux/seq_file.h>#include <linux/sched/debug.h> static inline void closure_put_after_sub_checks(int flags){	int r = flags & CLOSURE_REMAINING_MASK; 	if (WARN(flags & CLOSURE_GUARD_MASK,		 "closure has guard bits set: %x (%u)",		 flags & CLOSURE_GUARD_MASK, (unsigned) __fls(r)))		r &= ~CLOSURE_GUARD_MASK; 	WARN(!r && (flags & ~CLOSURE_DESTRUCTOR),	     "closure ref hit 0 with incorrect flags set: %x (%u)",	     flags & ~CLOSURE_DESTRUCTOR, (unsigned) __fls(flags));} static inline void closure_put_after_sub(struct closure *cl, int flags){	closure_put_after_sub_checks(flags); 	if (!(flags & CLOSURE_REMAINING_MASK)) {		smp_acquire__after_ctrl_dep(); 		cl->closure_get_happened = false; 		if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {			atomic_set(&cl->remaining,				   CLOSURE_REMAINING_INITIALIZER);			closure_queue(cl);		} else {			struct closure *parent = cl->parent;			closure_fn *destructor = cl->fn; 			closure_debug_destroy(cl); 			if (destructor)				destructor(&cl->work); 			if (parent)				closure_put(parent);		}	}} /* For clearing flags with the same atomic op as a put */void closure_sub(struct closure *cl, int v){	closure_put_after_sub(cl, atomic_sub_return_release(v, &cl->remaining));}EXPORT_SYMBOL(closure_sub); /* * closure_put - decrement a closure's refcount */void closure_put(struct closure *cl){	closure_put_after_sub(cl, atomic_dec_return_release(&cl->remaining));}EXPORT_SYMBOL(closure_put); /* * closure_wake_up - wake up all closures on a wait list, without memory barrier */void __closure_wake_up(struct closure_waitlist *wait_list){	struct llist_node *list;	struct closure *cl, *t;	struct llist_node *reverse = NULL; 	list = llist_del_all(&wait_list->list); 	/* We first reverse the list to preserve FIFO ordering and fairness */	reverse = llist_reverse_order(list); 	/* Then do the wakeups */	llist_for_each_entry_safe(cl, t, reverse, list) {		closure_set_waiting(cl, 0);		closure_sub(cl, CLOSURE_WAITING + 1);	}}EXPORT_SYMBOL(__closure_wake_up); /** * closure_wait - add a closure to a waitlist * @waitlist: will own a ref on @cl, which will be released when * closure_wake_up() is called on @waitlist. * @cl: closure pointer. * */bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl){	if (atomic_read(&cl->remaining) & CLOSURE_WAITING)		return false; 	cl->closure_get_happened = true;	closure_set_waiting(cl, _RET_IP_);	atomic_add(CLOSURE_WAITING + 1, &cl->remaining);	llist_add(&cl->list, &waitlist->list); 	return true;}EXPORT_SYMBOL(closure_wait); struct closure_syncer {	struct task_struct	*task;	int			done;}; static CLOSURE_CALLBACK(closure_sync_fn){	struct closure *cl = container_of(ws, struct closure, work);	struct closure_syncer *s = cl->s;	struct task_struct *p; 	rcu_read_lock();	p = READ_ONCE(s->task);	s->done = 1;	wake_up_process(p);	rcu_read_unlock();} void __sched __closure_sync(struct closure *cl){	struct closure_syncer s = { .task = current }; 	cl->s = &s;	continue_at(cl, closure_sync_fn, NULL); 	while (1) {		set_current_state(TASK_UNINTERRUPTIBLE);		if (s.done)			break;		schedule();	} 	__set_current_state(TASK_RUNNING);}EXPORT_SYMBOL(__closure_sync); /* * closure_return_sync - finish running a closure, synchronously (i.e. waiting * for outstanding get()s to finish) and returning once closure refcount is 0. * * Unlike closure_sync() this doesn't reinit the ref to 1; subsequent * closure_get_not_zero() calls waill fail. */void __sched closure_return_sync(struct closure *cl){	struct closure_syncer s = { .task = current }; 	cl->s = &s;	set_closure_fn(cl, closure_sync_fn, NULL); 	unsigned flags = atomic_sub_return_release(1 + CLOSURE_RUNNING - CLOSURE_DESTRUCTOR,						   &cl->remaining); 	closure_put_after_sub_checks(flags); 	if (unlikely(flags & CLOSURE_REMAINING_MASK)) {		while (1) {			set_current_state(TASK_UNINTERRUPTIBLE);			if (s.done)				break;			schedule();		} 		__set_current_state(TASK_RUNNING);	} 	if (cl->parent)		closure_put(cl->parent);}EXPORT_SYMBOL(closure_return_sync); int __sched __closure_sync_timeout(struct closure *cl, unsigned long timeout){	struct closure_syncer s = { .task = current };	int ret = 0; 	cl->s = &s;	continue_at(cl, closure_sync_fn, NULL); 	while (1) {		set_current_state(TASK_UNINTERRUPTIBLE);		if (s.done)			break;		if (!timeout) {			/*			 * Carefully undo the continue_at() - but only if it			 * hasn't completed, i.e. the final closure_put() hasn't			 * happened yet:			 */			unsigned old, new, v = atomic_read(&cl->remaining);			do {				old = v;				if (!old || (old & CLOSURE_RUNNING))					goto success; 				new = old + CLOSURE_REMAINING_INITIALIZER;			} while ((v = atomic_cmpxchg(&cl->remaining, old, new)) != old);			ret = -ETIME;		} 		timeout = schedule_timeout(timeout);	}success:	__set_current_state(TASK_RUNNING);	return ret;}EXPORT_SYMBOL(__closure_sync_timeout); #ifdef CONFIG_DEBUG_CLOSURES static LIST_HEAD(closure_list);static DEFINE_SPINLOCK(closure_list_lock); void closure_debug_create(struct closure *cl){	unsigned long flags; 	BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);	cl->magic = CLOSURE_MAGIC_ALIVE; 	spin_lock_irqsave(&closure_list_lock, flags);	list_add(&cl->all, &closure_list);	spin_unlock_irqrestore(&closure_list_lock, flags);}EXPORT_SYMBOL(closure_debug_create); void closure_debug_destroy(struct closure *cl){	unsigned long flags; 	if (cl->magic == CLOSURE_MAGIC_STACK)		return; 	BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);	cl->magic = CLOSURE_MAGIC_DEAD; 	spin_lock_irqsave(&closure_list_lock, flags);	list_del(&cl->all);	spin_unlock_irqrestore(&closure_list_lock, flags);}EXPORT_SYMBOL(closure_debug_destroy); static int debug_show(struct seq_file *f, void *data){	struct closure *cl; 	spin_lock_irq(&closure_list_lock); 	list_for_each_entry(cl, &closure_list, all) {		int r = atomic_read(&cl->remaining); 		seq_printf(f, "%p: %pS -> %pS p %p r %i ",			   cl, (void *) cl->ip, cl->fn, cl->parent,			   r & CLOSURE_REMAINING_MASK); 		seq_printf(f, "%s%s\n",			   test_bit(WORK_STRUCT_PENDING_BIT,				    work_data_bits(&cl->work)) ? "Q" : "",			   r & CLOSURE_RUNNING	? "R" : ""); 		if (r & CLOSURE_WAITING)			seq_printf(f, " W %pS\n",				   (void *) cl->waiting_on); 		seq_putc(f, '\n');	} 	spin_unlock_irq(&closure_list_lock);	return 0;} DEFINE_SHOW_ATTRIBUTE(debug); static int __init closure_debug_init(void){	debugfs_create_file("closures", 0400, NULL, NULL, &debug_fops);	return 0;}late_initcall(closure_debug_init) #endif