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, 75 struct ww_acquire_ctx *ctx, int catch_signal) 76 { 77 struct task_struct *task; 78 struct ww_mutex_thread entry; 79 struct ww_mutex_thread *other; 80 int retval = 0; 81 82 task = current; 83 84 linux_ww_lock(); 85 if (unlikely(sx_try_xlock(&lock->base.sx) == 0)) { 86 entry.thread = curthread; 87 entry.lock = lock; 88 TAILQ_INSERT_TAIL(&ww_mutex_head, &entry, entry); 89 90 do { 91 struct thread *owner = (struct thread *) 92 SX_OWNER(lock->base.sx.sx_lock); 93 94 /* scan for deadlock */ 95 TAILQ_FOREACH(other, &ww_mutex_head, entry) { 96 /* skip own thread */ 97 if (other == &entry) 98 continue; 99 /* 100 * If another thread is owning our 101 * lock and is at the same time trying 102 * to acquire a lock this thread owns, 103 * that means deadlock. 104 */ 105 if (other->thread == owner && 106 (struct thread *)SX_OWNER( 107 other->lock->base.sx.sx_lock) == curthread) { 108 retval = -EDEADLK; 109 goto done; 110 } 111 } 112 if (catch_signal) { 113 retval = -cv_wait_sig(&lock->condvar, &ww_mutex_global); 114 if (retval != 0) { 115 linux_schedule_save_interrupt_value(task, retval); 116 retval = -EINTR; 117 goto done; 118 } 119 } else { 120 cv_wait(&lock->condvar, &ww_mutex_global); 121 } 122 } while (sx_try_xlock(&lock->base.sx) == 0); 123 done: 124 TAILQ_REMOVE(&ww_mutex_head, &entry, entry); 125 126 /* if the lock is free, wakeup next lock waiter, if any */ 127 if ((struct thread *)SX_OWNER(lock->base.sx.sx_lock) == NULL) 128 cv_signal(&lock->condvar); 129 } 130 131 if (retval == 0) 132 lock->ctx = ctx; 133 linux_ww_unlock(); 134 return (retval); 135 } 136 137 void 138 linux_ww_mutex_unlock_sub(struct ww_mutex *lock) 139 { 140 /* protect ww_mutex ownership change */ 141 linux_ww_lock(); 142 lock->ctx = NULL; 143 sx_xunlock(&lock->base.sx); 144 /* wakeup a lock waiter, if any */ 145 cv_signal(&lock->condvar); 146 linux_ww_unlock(); 147 } 148 149 int 150 linux_mutex_lock_interruptible(mutex_t *m) 151 { 152 int error; 153 154 error = -sx_xlock_sig(&m->sx); 155 if (error != 0) { 156 linux_schedule_save_interrupt_value(current, error); 157 error = -EINTR; 158 } 159 return (error); 160 } 161 162 int 163 linux_down_write_killable(struct rw_semaphore *rw) 164 { 165 int error; 166 167 error = -sx_xlock_sig(&rw->sx); 168 if (error != 0) { 169 linux_schedule_save_interrupt_value(current, error); 170 error = -EINTR; 171 } 172 return (error); 173 } 174