1 /*
2  * Copyright (c) 2016 Mellanox Technologies Ltd. All rights reserved.
3  * Copyright (c) 2015 System Fabric Works, Inc. All rights reserved.
4  *
5  * This software is available to you under a choice of one of two
6  * licenses.  You may choose to be licensed under the terms of the GNU
7  * General Public License (GPL) Version 2, available from the file
8  * COPYING in the main directory of this source tree, or the
9  * OpenIB.org BSD license below:
10  *
11  *	   Redistribution and use in source and binary forms, with or
12  *	   without modification, are permitted provided that the following
13  *	   conditions are met:
14  *
15  *	- Redistributions of source code must retain the above
16  *	  copyright notice, this list of conditions and the following
17  *	  disclaimer.
18  *
19  *	- Redistributions in binary form must reproduce the above
20  *	  copyright notice, this list of conditions and the following
21  *	  disclaimer in the documentation and/or other materials
22  *	  provided with the distribution.
23  *
24  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
25  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
26  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
27  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
28  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
29  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
30  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
31  * SOFTWARE.
32  */
33 
34 #include <linux/kernel.h>
35 #include <linux/interrupt.h>
36 #include <linux/hardirq.h>
37 
38 #include "rxe_task.h"
39 
40 int __rxe_do_task(struct rxe_task *task)
41 
42 {
43 	int ret;
44 
45 	while ((ret = task->func(task->arg)) == 0)
46 		;
47 
48 	task->ret = ret;
49 
50 	return ret;
51 }
52 
53 /*
54  * this locking is due to a potential race where
55  * a second caller finds the task already running
56  * but looks just after the last call to func
57  */
58 void rxe_do_task(unsigned long data)
59 {
60 	int cont;
61 	int ret;
62 	unsigned long flags;
63 	struct rxe_task *task = (struct rxe_task *)data;
64 
65 	spin_lock_irqsave(&task->state_lock, flags);
66 	switch (task->state) {
67 	case TASK_STATE_START:
68 		task->state = TASK_STATE_BUSY;
69 		spin_unlock_irqrestore(&task->state_lock, flags);
70 		break;
71 
72 	case TASK_STATE_BUSY:
73 		task->state = TASK_STATE_ARMED;
74 		fallthrough;
75 	case TASK_STATE_ARMED:
76 		spin_unlock_irqrestore(&task->state_lock, flags);
77 		return;
78 
79 	default:
80 		spin_unlock_irqrestore(&task->state_lock, flags);
81 		pr_warn("%s failed with bad state %d\n", __func__, task->state);
82 		return;
83 	}
84 
85 	do {
86 		cont = 0;
87 		ret = task->func(task->arg);
88 
89 		spin_lock_irqsave(&task->state_lock, flags);
90 		switch (task->state) {
91 		case TASK_STATE_BUSY:
92 			if (ret)
93 				task->state = TASK_STATE_START;
94 			else
95 				cont = 1;
96 			break;
97 
98 		/* soneone tried to run the task since the last time we called
99 		 * func, so we will call one more time regardless of the
100 		 * return value
101 		 */
102 		case TASK_STATE_ARMED:
103 			task->state = TASK_STATE_BUSY;
104 			cont = 1;
105 			break;
106 
107 		default:
108 			pr_warn("%s failed with bad state %d\n", __func__,
109 				task->state);
110 		}
111 		spin_unlock_irqrestore(&task->state_lock, flags);
112 	} while (cont);
113 
114 	task->ret = ret;
115 }
116 
117 int rxe_init_task(void *obj, struct rxe_task *task,
118 		  void *arg, int (*func)(void *), char *name)
119 {
120 	task->obj	= obj;
121 	task->arg	= arg;
122 	task->func	= func;
123 	snprintf(task->name, sizeof(task->name), "%s", name);
124 	task->destroyed	= false;
125 
126 	tasklet_init(&task->tasklet, rxe_do_task, (unsigned long)task);
127 
128 	task->state = TASK_STATE_START;
129 	spin_lock_init(&task->state_lock);
130 
131 	return 0;
132 }
133 
134 void rxe_cleanup_task(struct rxe_task *task)
135 {
136 	unsigned long flags;
137 	bool idle;
138 
139 	/*
140 	 * Mark the task, then wait for it to finish. It might be
141 	 * running in a non-tasklet (direct call) context.
142 	 */
143 	task->destroyed = true;
144 
145 	do {
146 		spin_lock_irqsave(&task->state_lock, flags);
147 		idle = (task->state == TASK_STATE_START);
148 		spin_unlock_irqrestore(&task->state_lock, flags);
149 	} while (!idle);
150 
151 	tasklet_kill(&task->tasklet);
152 }
153 
154 void rxe_run_task(struct rxe_task *task, int sched)
155 {
156 	if (task->destroyed)
157 		return;
158 
159 	if (sched)
160 		tasklet_schedule(&task->tasklet);
161 	else
162 		rxe_do_task((unsigned long)task);
163 }
164 
165 void rxe_disable_task(struct rxe_task *task)
166 {
167 	tasklet_disable(&task->tasklet);
168 }
169 
170 void rxe_enable_task(struct rxe_task *task)
171 {
172 	tasklet_enable(&task->tasklet);
173 }
174