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 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 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 61 linux_ww_lock(void) 62 { 63 mtx_lock(&ww_mutex_global); 64 } 65 66 static inline void 67 linux_ww_unlock(void) 68 { 69 mtx_unlock(&ww_mutex_global); 70 } 71 72 /* lock a mutex with deadlock avoidance */ 73 int 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 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 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 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