usr/src/lib/libtnfctl/prb_shmem.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  * Copyright (c) 1994, by Sun Microsytems, Inc.
  24  */
  25
  26 #pragma ident   "%Z%%M% %I%     %E% SMI"
  27
  28 /*
  29  * Interfaces to allocate, control, and free a shared memory lock
  30  * XXXX Could we use a semaphore or a shared memory condition variable
  31  * instead ?
  32  */
  33
  34 #include <unistd.h>
  35 #include <fcntl.h>
  36 #include <errno.h>
  37 #include <stdlib.h>
  38 #include <sys/mman.h>
  39 #include <sys/types.h>
  40
  41 #include "prb_proc_int.h"
  42 #include "dbg.h"
  43
  44 static boolean_t getspin(volatile shmem_msg_t *smp);
  45
  46 /*
  47  * prb_shmem_init() - Allocates and initializes the shared memory region
  48  */
  49 prb_status_t
  50 prb_shmem_init(volatile shmem_msg_t **ret_val)
  51 {
  52         int             shmem_fd;
  53         volatile        shmem_msg_t *smp;
  54
  55         DBG_TNF_PROBE_0(prb_shmem_init_1, "libtnfctl", "sunw%verbosity 2");
  56
  57         shmem_fd = open("/dev/zero", O_RDWR);
  58         if (shmem_fd == -1) {
  59                 DBG((void) fprintf(stderr, "couldn't open \"/dev/zero\""));
  60                 return (prb_status_map(errno));
  61         }
  62         /*LINTED pointer cast may result in improper alignment*/
  63         smp = (shmem_msg_t *) mmap(0, sizeof (struct shmem_msg),
  64                         PROT_READ | PROT_WRITE, MAP_SHARED,
  65                         shmem_fd, 0);
  66         if (smp == (struct shmem_msg *) - 1) {
  67                 DBG((void) fprintf(stderr, "couldn't mmap \"/dev/zero\""));
  68                 return (prb_status_map(errno));
  69         }
  70         (void) close(shmem_fd);
  71
  72         /* sets the shared memory region to cause waiting */
  73         smp->spin = B_TRUE;
  74
  75         *ret_val = smp;
  76
  77         return (PRB_STATUS_OK);
  78 }
  79
  80 /*
  81  * prb_shmem_wait() - spins until the shared memory flag is cleared
  82  */
  83 static boolean_t
  84 getspin(volatile shmem_msg_t *smp)
  85 {
  86         return (smp->spin);
  87 }
  88
  89 prb_status_t
  90 prb_shmem_wait(volatile shmem_msg_t *smp)
  91 {
  92         DBG_TNF_PROBE_0(prb_shmem_wait_start, "libtnfctl",
  93                 "sunw%verbosity 2; start prb_shmem_wait");
  94
  95         while (getspin(smp));
  96
  97         DBG_TNF_PROBE_0(prb_shmem_wait_end, "libtnfctl",
  98                 "sunw%verbosity 2; end prb_shmem_wait");
  99
 100         return (PRB_STATUS_OK);
 101
 102 }
 103
 104
 105 /*
 106  * prb_shmem_clear() - clears the shared memory flag and allows waiters to
 107  * proceed.
 108  */
 109 prb_status_t
 110 prb_shmem_clear(volatile shmem_msg_t *smp)
 111 {
 112         DBG_TNF_PROBE_0(prb_shmem_clear_1, "libtnfctl", "sunw%verbosity 2");
 113
 114         smp->spin = B_FALSE;
 115
 116         return (PRB_STATUS_OK);
 117 }
 118
 119 /*
 120  * prb_shmem_free() - Unmaps the shared memory region.
 121  */
 122 prb_status_t
 123 prb_shmem_free(volatile shmem_msg_t *smp)
 124 {
 125         DBG_TNF_PROBE_0(prb_shmem_free_1, "libtnfctl", "sunw%verbosity 2");
 126
 127         if (munmap((caddr_t) smp, sizeof (struct shmem_msg)) != 0) {
 128                 DBG((void) fprintf(stderr, "couldn't munmap shared memory\n"));
 129                 return (prb_status_map(errno));
 130         }
 131
 132         return (PRB_STATUS_OK);
 133 }