filemon_lock.c

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    1 /*-
    2  * Copyright (c) 2009-2011, Juniper Networks, Inc.
    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, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY JUNIPER NETWORKS AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED. IN NO EVENT SHALL JUNIPER NETWORKS OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  */
   26 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD$");
   29 
   30 static void
   31 filemon_filemon_lock(struct filemon *filemon)
   32 {
   33         mtx_lock(&filemon->mtx);
   34 
   35         while (filemon->locker != NULL && filemon->locker != curthread)
   36                 cv_wait(&filemon->cv, &filemon->mtx);
   37 
   38         filemon->locker = curthread;
   39 
   40         mtx_unlock(&filemon->mtx);
   41 }
   42 
   43 static void
   44 filemon_filemon_unlock(struct filemon *filemon)
   45 {
   46         mtx_lock(&filemon->mtx);
   47 
   48         if (filemon->locker == curthread)
   49                 filemon->locker = NULL;
   50 
   51         /* Wake up threads waiting. */
   52         cv_broadcast(&filemon->cv);
   53 
   54         mtx_unlock(&filemon->mtx);
   55 }
   56 
   57 static void
   58 filemon_lock_read(void)
   59 {
   60         mtx_lock(&access_mtx);
   61 
   62         while (access_owner != NULL || access_requester != NULL)
   63                 cv_wait(&access_cv, &access_mtx);
   64 
   65         n_readers++;
   66 
   67         /* Wake up threads waiting. */
   68         cv_broadcast(&access_cv);
   69 
   70         mtx_unlock(&access_mtx);
   71 }
   72 
   73 static void
   74 filemon_unlock_read(void)
   75 {
   76         mtx_lock(&access_mtx);
   77 
   78         if (n_readers > 0)
   79                 n_readers--;
   80 
   81         /* Wake up a thread waiting. */
   82         cv_broadcast(&access_cv);
   83 
   84         mtx_unlock(&access_mtx);
   85 }
   86 
   87 static void
   88 filemon_lock_write(void)
   89 {
   90         mtx_lock(&access_mtx);
   91 
   92         while (access_owner != curthread) {
   93                 if (access_owner == NULL &&
   94                     (access_requester == NULL ||
   95                     access_requester == curthread)) {
   96                         access_owner = curthread;
   97                         access_requester = NULL;
   98                 } else {
   99                         if (access_requester == NULL)
  100                                 access_requester = curthread;
  101 
  102                         cv_wait(&access_cv, &access_mtx);
  103                 }
  104         }
  105 
  106         mtx_unlock(&access_mtx);
  107 }
  108 
  109 static void
  110 filemon_unlock_write(void)
  111 {
  112         mtx_lock(&access_mtx);
  113 
  114         /* Sanity check that the current thread actually has the write lock. */
  115         if (access_owner == curthread)
  116                 access_owner = NULL;
  117 
  118         /* Wake up a thread waiting. */
  119         cv_broadcast(&access_cv);
  120 
  121         mtx_unlock(&access_mtx);
  122 }

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FreeBSD/Linux Kernel Cross Reference sys/dev/filemon/filemon_lock.c

FreeBSD/Linux Kernel Cross Reference
sys/dev/filemon/filemon_lock.c