1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Copyright (C) 2003-2008 Takahiro Hirofuchi
4  * Copyright (C) 2015 Nobuo Iwata
5  */
6 
7 #include <linux/kthread.h>
8 #include <linux/export.h>
9 #include <linux/slab.h>
10 #include <linux/workqueue.h>
11 
12 #include "usbip_common.h"
13 
14 struct usbip_event {
15 	struct list_head node;
16 	struct usbip_device *ud;
17 };
18 
19 static DEFINE_SPINLOCK(event_lock);
20 static LIST_HEAD(event_list);
21 
set_event(struct usbip_device * ud,unsigned long event)22 static void set_event(struct usbip_device *ud, unsigned long event)
23 {
24 	unsigned long flags;
25 
26 	spin_lock_irqsave(&ud->lock, flags);
27 	ud->event |= event;
28 	spin_unlock_irqrestore(&ud->lock, flags);
29 }
30 
unset_event(struct usbip_device * ud,unsigned long event)31 static void unset_event(struct usbip_device *ud, unsigned long event)
32 {
33 	unsigned long flags;
34 
35 	spin_lock_irqsave(&ud->lock, flags);
36 	ud->event &= ~event;
37 	spin_unlock_irqrestore(&ud->lock, flags);
38 }
39 
get_event(void)40 static struct usbip_device *get_event(void)
41 {
42 	struct usbip_event *ue = NULL;
43 	struct usbip_device *ud = NULL;
44 	unsigned long flags;
45 
46 	spin_lock_irqsave(&event_lock, flags);
47 	if (!list_empty(&event_list)) {
48 		ue = list_first_entry(&event_list, struct usbip_event, node);
49 		list_del(&ue->node);
50 	}
51 	spin_unlock_irqrestore(&event_lock, flags);
52 
53 	if (ue) {
54 		ud = ue->ud;
55 		kfree(ue);
56 	}
57 	return ud;
58 }
59 
60 static struct task_struct *worker_context;
61 
event_handler(struct work_struct * work)62 static void event_handler(struct work_struct *work)
63 {
64 	struct usbip_device *ud;
65 
66 	if (worker_context == NULL) {
67 		worker_context = current;
68 	}
69 
70 	while ((ud = get_event()) != NULL) {
71 		usbip_dbg_eh("pending event %lx\n", ud->event);
72 
73 		mutex_lock(&ud->sysfs_lock);
74 		/*
75 		 * NOTE: shutdown must come first.
76 		 * Shutdown the device.
77 		 */
78 		if (ud->event & USBIP_EH_SHUTDOWN) {
79 			ud->eh_ops.shutdown(ud);
80 			unset_event(ud, USBIP_EH_SHUTDOWN);
81 		}
82 
83 		/* Reset the device. */
84 		if (ud->event & USBIP_EH_RESET) {
85 			ud->eh_ops.reset(ud);
86 			unset_event(ud, USBIP_EH_RESET);
87 		}
88 
89 		/* Mark the device as unusable. */
90 		if (ud->event & USBIP_EH_UNUSABLE) {
91 			ud->eh_ops.unusable(ud);
92 			unset_event(ud, USBIP_EH_UNUSABLE);
93 		}
94 		mutex_unlock(&ud->sysfs_lock);
95 
96 		wake_up(&ud->eh_waitq);
97 	}
98 }
99 
usbip_start_eh(struct usbip_device * ud)100 int usbip_start_eh(struct usbip_device *ud)
101 {
102 	init_waitqueue_head(&ud->eh_waitq);
103 	ud->event = 0;
104 	return 0;
105 }
106 EXPORT_SYMBOL_GPL(usbip_start_eh);
107 
usbip_stop_eh(struct usbip_device * ud)108 void usbip_stop_eh(struct usbip_device *ud)
109 {
110 	unsigned long pending = ud->event & ~USBIP_EH_BYE;
111 
112 	if (!(ud->event & USBIP_EH_BYE))
113 		usbip_dbg_eh("usbip_eh stopping but not removed\n");
114 
115 	if (pending)
116 		usbip_dbg_eh("usbip_eh waiting completion %lx\n", pending);
117 
118 	wait_event_interruptible(ud->eh_waitq, !(ud->event & ~USBIP_EH_BYE));
119 	usbip_dbg_eh("usbip_eh has stopped\n");
120 }
121 EXPORT_SYMBOL_GPL(usbip_stop_eh);
122 
123 #define WORK_QUEUE_NAME "usbip_event"
124 
125 static struct workqueue_struct *usbip_queue;
126 static DECLARE_WORK(usbip_work, event_handler);
127 
usbip_init_eh(void)128 int usbip_init_eh(void)
129 {
130 	usbip_queue = create_singlethread_workqueue(WORK_QUEUE_NAME);
131 	if (usbip_queue == NULL) {
132 		pr_err("failed to create usbip_event\n");
133 		return -ENOMEM;
134 	}
135 	return 0;
136 }
137 
usbip_finish_eh(void)138 void usbip_finish_eh(void)
139 {
140 	flush_workqueue(usbip_queue);
141 	destroy_workqueue(usbip_queue);
142 	usbip_queue = NULL;
143 }
144 
usbip_event_add(struct usbip_device * ud,unsigned long event)145 void usbip_event_add(struct usbip_device *ud, unsigned long event)
146 {
147 	struct usbip_event *ue;
148 	unsigned long flags;
149 
150 	if (ud->event & USBIP_EH_BYE)
151 		return;
152 
153 	set_event(ud, event);
154 
155 	spin_lock_irqsave(&event_lock, flags);
156 
157 	list_for_each_entry_reverse(ue, &event_list, node) {
158 		if (ue->ud == ud)
159 			goto out;
160 	}
161 
162 	ue = kmalloc(sizeof(struct usbip_event), GFP_ATOMIC);
163 	if (ue == NULL)
164 		goto out;
165 
166 	ue->ud = ud;
167 
168 	list_add_tail(&ue->node, &event_list);
169 	queue_work(usbip_queue, &usbip_work);
170 
171 out:
172 	spin_unlock_irqrestore(&event_lock, flags);
173 }
174 EXPORT_SYMBOL_GPL(usbip_event_add);
175 
usbip_event_happened(struct usbip_device * ud)176 int usbip_event_happened(struct usbip_device *ud)
177 {
178 	int happened = 0;
179 	unsigned long flags;
180 
181 	spin_lock_irqsave(&ud->lock, flags);
182 	if (ud->event != 0)
183 		happened = 1;
184 	spin_unlock_irqrestore(&ud->lock, flags);
185 
186 	return happened;
187 }
188 EXPORT_SYMBOL_GPL(usbip_event_happened);
189 
usbip_in_eh(struct task_struct * task)190 int usbip_in_eh(struct task_struct *task)
191 {
192 	if (task == worker_context)
193 		return 1;
194 
195 	return 0;
196 }
197 EXPORT_SYMBOL_GPL(usbip_in_eh);
198