sys/compat/linuxkpi/common/src/linux_lock.c

   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/ww_mutex.h>
  32
  33 struct ww_mutex_thread {
  34         TAILQ_ENTRY(ww_mutex_thread) entry;
  35         struct thread *thread;
  36         struct ww_mutex *lock;
  37 };
  38
  39 static TAILQ_HEAD(, ww_mutex_thread) ww_mutex_head;
  40 static struct mtx ww_mutex_global;
  41
  42 static void
  43 linux_ww_init(void *arg)
  44 {
  45         TAILQ_INIT(&ww_mutex_head);
  46         mtx_init(&ww_mutex_global, "lkpi-ww-mtx", NULL, MTX_DEF);
  47 }
  48
  49 SYSINIT(ww_init, SI_SUB_LOCK, SI_ORDER_SECOND, linux_ww_init, NULL);
  50
  51 static void
  52 linux_ww_uninit(void *arg)
  53 {
  54         mtx_destroy(&ww_mutex_global);
  55 }
  56
  57 SYSUNINIT(ww_uninit, SI_SUB_LOCK, SI_ORDER_SECOND, linux_ww_uninit, NULL);
  58
  59 static inline void
  60 linux_ww_lock(void)
  61 {
  62         mtx_lock(&ww_mutex_global);
  63 }
  64
  65 static inline void
  66 linux_ww_unlock(void)
  67 {
  68         mtx_unlock(&ww_mutex_global);
  69 }
  70
  71 /* lock a mutex with deadlock avoidance */
  72 int
  73 linux_ww_mutex_lock_sub(struct ww_mutex *lock, int catch_signal)
  74 {
  75         struct ww_mutex_thread entry;
  76         struct ww_mutex_thread *other;
  77         int retval = 0;
  78
  79         linux_ww_lock();
  80         if (unlikely(sx_try_xlock(&lock->base.sx) == 0)) {
  81                 entry.thread = curthread;
  82                 entry.lock = lock;
  83                 TAILQ_INSERT_TAIL(&ww_mutex_head, &entry, entry);
  84
  85                 do {
  86                         struct thread *owner = (struct thread *)
  87                             SX_OWNER(lock->base.sx.sx_lock);
  88
  89                         /* scan for deadlock */
  90                         TAILQ_FOREACH(other, &ww_mutex_head, entry) {
  91                                 /* skip own thread */
  92                                 if (other == &entry)
  93                                         continue;
  94                                 /*
  95                                  * If another thread is owning our
  96                                  * lock and is at the same time trying
  97                                  * to acquire a lock this thread owns,
  98                                  * that means deadlock.
  99                                  */
 100                                 if (other->thread == owner &&
 101                                     (struct thread *)SX_OWNER(
 102                                     other->lock->base.sx.sx_lock) == curthread) {
 103                                         retval = -EDEADLK;
 104                                         goto done;
 105                                 }
 106                         }
 107                         if (catch_signal) {
 108                                 if (cv_wait_sig(&lock->condvar, &ww_mutex_global) != 0) {
 109                                         retval = -EINTR;
 110                                         goto done;
 111                                 }
 112                         } else {
 113                                 cv_wait(&lock->condvar, &ww_mutex_global);
 114                         }
 115                 } while (sx_try_xlock(&lock->base.sx) == 0);
 116 done:
 117                 TAILQ_REMOVE(&ww_mutex_head, &entry, entry);
 118
 119                 /* if the lock is free, wakeup next lock waiter, if any */
 120                 if ((struct thread *)SX_OWNER(lock->base.sx.sx_lock) == NULL)
 121                         cv_signal(&lock->condvar);
 122         }
 123         linux_ww_unlock();
 124         return (retval);
 125 }
 126
 127 void
 128 linux_ww_mutex_unlock_sub(struct ww_mutex *lock)
 129 {
 130         /* protect ww_mutex ownership change */
 131         linux_ww_lock();
 132         sx_xunlock(&lock->base.sx);
 133         /* wakeup a lock waiter, if any */
 134         cv_signal(&lock->condvar);
 135         linux_ww_unlock();
 136 }