usr/src/lib/libnsl/rpc/fdsync.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22
  23 /*
  24  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
  25  * Use is subject to license terms.
  26  */
  27
  28 #pragma ident   "%Z%%M% %I%     %E% SMI"
  29
  30 /*
  31  * This file contains functions that enables the rpc library to synchronize
  32  * between various threads while they compete for a particular file descriptor.
  33  */
  34
  35 #include "mt.h"
  36 #include "rpc_mt.h"
  37 #include <rpc/rpc.h>
  38 #include <errno.h>
  39 #include <sys/poll.h>
  40 #include <syslog.h>
  41 #include <sys/types.h>
  42 #include <stdlib.h>
  43 #include <unistd.h>
  44
  45 /*
  46  * A block holds an array of maxBlockSize cell and associated recursive locks
  47  */
  48
  49 #define CELLTBLSZ       1024
  50
  51 typedef struct rpcfd_block {
  52         struct rpcfd_block *next;       /* Next Block */
  53         struct rpcfd_block *prev;       /* prev Block */
  54         int     end;                    /* fd of last lock in the list */
  55         mutex_t lock[CELLTBLSZ];        /* recursive locks */
  56 } rpcfd_block_t;
  57
  58 mutex_t rpc_fd_list_lock = DEFAULTMUTEX;        /* protects list manipulation */
  59
  60 /* Following functions create and manipulates the dgfd lock object */
  61
  62 static mutex_t *search(const void *handle, int fd);
  63 static rpcfd_block_t *create_block(const void *handle, int fd);
  64
  65 void *
  66 rpc_fd_init(void)
  67 {
  68         /*
  69          * Create first chunk of CELLTBLSZ
  70          * (No lock is required for initial creation.)
  71          */
  72         return (create_block(NULL, 0));
  73 }
  74
  75 /*
  76  * If rpc_fd_lock() fails to acquire a lock, it returns non-zero (ENOMEM).
  77  * (The operation can only fail due to a malloc() failure.)
  78  * The caller of rpc_fd_lock() must call rpc_fd_unlock() even if
  79  * rpc_fd_lock() failed.  This keeps _sigoff() and _sigon() balanced.
  80  *
  81  * If search() and create_block() fail for rpc_fd_lock(), then search()
  82  * will fail for rpc_fd_unlock(), so mutex_lock() and mutex_unlock()
  83  * calls will be balanced.  In any case, since the mutex is marked
  84  * LOCK_ERRORCHECK, an additional mutex_unlock() does nothing.
  85  */
  86 int
  87 rpc_fd_lock(const void *handle, int fd)
  88 {
  89         mutex_t *mp;
  90         rpcfd_block_t *p;
  91
  92         _sigoff();
  93         (void) mutex_lock(&rpc_fd_list_lock);
  94         mp = search(handle, fd);
  95         if (mp == NULL) {
  96                 p = create_block(handle, fd);
  97                 if (p != NULL)
  98                         mp = &p->lock[fd % CELLTBLSZ];
  99         }
 100         (void) mutex_unlock(&rpc_fd_list_lock);
 101         if (mp == NULL)
 102                 return (ENOMEM);
 103         (void) mutex_lock(mp);
 104         return (0);
 105 }
 106
 107 void
 108 rpc_fd_unlock(const void *handle, int fd)
 109 {
 110         mutex_t *mp;
 111
 112         (void) mutex_lock(&rpc_fd_list_lock);
 113         mp = search(handle, fd);
 114         (void) mutex_unlock(&rpc_fd_list_lock);
 115         if (mp != NULL)
 116                 (void) mutex_unlock(mp);
 117         _sigon();
 118 }
 119
 120 static rpcfd_block_t *
 121 create_block(const void *handle, int fd)
 122 {
 123         rpcfd_block_t *l, *lprev;
 124         rpcfd_block_t *p;
 125         int i;
 126
 127         p = malloc(sizeof (rpcfd_block_t));
 128         if (p == NULL)
 129                 return (NULL);
 130
 131         for (i = 0; i < CELLTBLSZ; i++) {
 132                 (void) mutex_init(&p->lock[i],
 133                         USYNC_THREAD | LOCK_RECURSIVE | LOCK_ERRORCHECK, NULL);
 134         }
 135         p->end = (((fd + CELLTBLSZ) / CELLTBLSZ) * CELLTBLSZ) - 1;
 136         lprev = NULL;
 137         for (l = (rpcfd_block_t *)handle; l; l = l->next) {
 138                 lprev = l;
 139                 if (fd < l->end)
 140                         break;
 141         }
 142
 143         p->next = l;
 144         p->prev = lprev;
 145         if (lprev)
 146                 lprev->next = p;
 147         if (l)
 148                 l->prev = p;
 149
 150         return (p);
 151 }
 152
 153 /*
 154  * Called with rpc_fd_list_lock held.
 155  */
 156 static mutex_t *
 157 search(const void *handle, int fd)
 158 {
 159         rpcfd_block_t *p;
 160
 161         for (p = (rpcfd_block_t *)handle; p; p = p->next) {
 162                 if (fd <= p->end)
 163                         return (&p->lock[fd % CELLTBLSZ]);
 164         }
 165
 166         return (NULL);
 167 }