1 /*-
2 * Copyright (c) 2017 Mellanox Technologies, Ltd.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice unmodified, this list of conditions, and the following
10 * disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 * $FreeBSD$
27 */
28
29 #include <sys/queue.h>
30
31 #include <linux/sched.h>
32 #include <linux/ww_mutex.h>
33
34 struct ww_mutex_thread {
35 TAILQ_ENTRY(ww_mutex_thread) entry;
36 struct thread *thread;
37 struct ww_mutex *lock;
38 };
39
40 static TAILQ_HEAD(, ww_mutex_thread) ww_mutex_head;
41 static struct mtx ww_mutex_global;
42
43 static void
linux_ww_init(void * arg)44 linux_ww_init(void *arg)
45 {
46 TAILQ_INIT(&ww_mutex_head);
47 mtx_init(&ww_mutex_global, "lkpi-ww-mtx", NULL, MTX_DEF);
48 }
49
50 SYSINIT(ww_init, SI_SUB_LOCK, SI_ORDER_SECOND, linux_ww_init, NULL);
51
52 static void
linux_ww_uninit(void * arg)53 linux_ww_uninit(void *arg)
54 {
55 mtx_destroy(&ww_mutex_global);
56 }
57
58 SYSUNINIT(ww_uninit, SI_SUB_LOCK, SI_ORDER_SECOND, linux_ww_uninit, NULL);
59
60 static inline void
linux_ww_lock(void)61 linux_ww_lock(void)
62 {
63 mtx_lock(&ww_mutex_global);
64 }
65
66 static inline void
linux_ww_unlock(void)67 linux_ww_unlock(void)
68 {
69 mtx_unlock(&ww_mutex_global);
70 }
71
72 /* lock a mutex with deadlock avoidance */
73 int
linux_ww_mutex_lock_sub(struct ww_mutex * lock,int catch_signal)74 linux_ww_mutex_lock_sub(struct ww_mutex *lock, int catch_signal)
75 {
76 struct task_struct *task;
77 struct ww_mutex_thread entry;
78 struct ww_mutex_thread *other;
79 int retval = 0;
80
81 task = current;
82
83 linux_ww_lock();
84 if (unlikely(sx_try_xlock(&lock->base.sx) == 0)) {
85 entry.thread = curthread;
86 entry.lock = lock;
87 TAILQ_INSERT_TAIL(&ww_mutex_head, &entry, entry);
88
89 do {
90 struct thread *owner = (struct thread *)
91 SX_OWNER(lock->base.sx.sx_lock);
92
93 /* scan for deadlock */
94 TAILQ_FOREACH(other, &ww_mutex_head, entry) {
95 /* skip own thread */
96 if (other == &entry)
97 continue;
98 /*
99 * If another thread is owning our
100 * lock and is at the same time trying
101 * to acquire a lock this thread owns,
102 * that means deadlock.
103 */
104 if (other->thread == owner &&
105 (struct thread *)SX_OWNER(
106 other->lock->base.sx.sx_lock) == curthread) {
107 retval = -EDEADLK;
108 goto done;
109 }
110 }
111 if (catch_signal) {
112 retval = -cv_wait_sig(&lock->condvar, &ww_mutex_global);
113 if (retval != 0) {
114 linux_schedule_save_interrupt_value(task, retval);
115 retval = -EINTR;
116 goto done;
117 }
118 } else {
119 cv_wait(&lock->condvar, &ww_mutex_global);
120 }
121 } while (sx_try_xlock(&lock->base.sx) == 0);
122 done:
123 TAILQ_REMOVE(&ww_mutex_head, &entry, entry);
124
125 /* if the lock is free, wakeup next lock waiter, if any */
126 if ((struct thread *)SX_OWNER(lock->base.sx.sx_lock) == NULL)
127 cv_signal(&lock->condvar);
128 }
129 linux_ww_unlock();
130 return (retval);
131 }
132
133 void
linux_ww_mutex_unlock_sub(struct ww_mutex * lock)134 linux_ww_mutex_unlock_sub(struct ww_mutex *lock)
135 {
136 /* protect ww_mutex ownership change */
137 linux_ww_lock();
138 sx_xunlock(&lock->base.sx);
139 /* wakeup a lock waiter, if any */
140 cv_signal(&lock->condvar);
141 linux_ww_unlock();
142 }
143
144 int
linux_mutex_lock_interruptible(mutex_t * m)145 linux_mutex_lock_interruptible(mutex_t *m)
146 {
147 int error;
148
149 error = -sx_xlock_sig(&m->sx);
150 if (error != 0) {
151 linux_schedule_save_interrupt_value(current, error);
152 error = -EINTR;
153 }
154 return (error);
155 }
156
157 int
linux_down_write_killable(struct rw_semaphore * rw)158 linux_down_write_killable(struct rw_semaphore *rw)
159 {
160 int error;
161
162 error = -sx_xlock_sig(&rw->sx);
163 if (error != 0) {
164 linux_schedule_save_interrupt_value(current, error);
165 error = -EINTR;
166 }
167 return (error);
168 }
169