202 lines
3.6 KiB
C
202 lines
3.6 KiB
C
/*
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* Copyright (c) 2000-2001, 2005 Sendmail, Inc. and its suppliers.
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* All rights reserved.
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*
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* By using this file, you agree to the terms and conditions set
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* forth in the LICENSE file which can be found at the top level of
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* the sendmail distribution.
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*/
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#include <sm/gen.h>
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SM_RCSID("@(#)$Id: sem.c,v 1.12 2005/03/25 21:27:02 ca Exp $")
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#if SM_CONF_SEM
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# include <stdlib.h>
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# include <unistd.h>
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# include <sm/sem.h>
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# include <sm/heap.h>
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/*
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** SM_SEM_START -- initialize semaphores
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**
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** Parameters:
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** key -- key for semaphores.
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** nsem -- number of semaphores.
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** semflg -- flag for semget(), if 0, use a default.
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** owner -- create semaphores.
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**
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** Returns:
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** id for semaphores.
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** < 0 on failure.
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*/
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int
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sm_sem_start(key, nsem, semflg, owner)
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key_t key;
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int nsem;
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int semflg;
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bool owner;
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{
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int semid, i;
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unsigned short *semvals;
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semvals = NULL;
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if (semflg == 0)
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semflg = (SEM_A|SEM_R)|((SEM_A|SEM_R) >> 3);
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if (owner)
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semflg |= IPC_CREAT|IPC_EXCL;
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semid = semget(key, nsem, semflg);
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if (semid < 0)
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goto error;
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if (owner)
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{
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union semun semarg;
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semvals = (unsigned short *) sm_malloc(nsem * sizeof semvals);
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if (semvals == NULL)
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goto error;
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semarg.array = semvals;
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/* initialize semaphore values to be available */
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for (i = 0; i < nsem; i++)
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semvals[i] = 1;
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if (semctl(semid, 0, SETALL, semarg) < 0)
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goto error;
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}
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return semid;
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error:
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if (semvals != NULL)
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sm_free(semvals);
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if (semid >= 0)
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sm_sem_stop(semid);
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return -1;
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}
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/*
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** SM_SEM_STOP -- stop using semaphores.
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**
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** Parameters:
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** semid -- id for semaphores.
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**
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** Returns:
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** 0 on success.
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** < 0 on failure.
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*/
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int
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sm_sem_stop(semid)
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int semid;
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{
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return semctl(semid, 0, IPC_RMID, NULL);
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}
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/*
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** SM_SEM_ACQ -- acquire semaphore.
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**
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** Parameters:
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** semid -- id for semaphores.
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** semnum -- number of semaphore.
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** timeout -- how long to wait for operation to succeed.
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**
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** Returns:
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** 0 on success.
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** < 0 on failure.
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*/
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int
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sm_sem_acq(semid, semnum, timeout)
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int semid;
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int semnum;
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int timeout;
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{
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int r;
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struct sembuf semops[1];
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semops[0].sem_num = semnum;
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semops[0].sem_op = -1;
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semops[0].sem_flg = SEM_UNDO |
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(timeout != SM_TIME_FOREVER ? 0 : IPC_NOWAIT);
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if (timeout == SM_TIME_IMMEDIATE || timeout == SM_TIME_FOREVER)
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return semop(semid, semops, 1);
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do
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{
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r = semop(semid, semops, 1);
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if (r == 0)
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return r;
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sleep(1);
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--timeout;
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} while (timeout > 0);
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return r;
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}
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/*
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** SM_SEM_REL -- release semaphore.
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**
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** Parameters:
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** semid -- id for semaphores.
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** semnum -- number of semaphore.
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** timeout -- how long to wait for operation to succeed.
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**
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** Returns:
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** 0 on success.
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** < 0 on failure.
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*/
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int
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sm_sem_rel(semid, semnum, timeout)
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int semid;
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int semnum;
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int timeout;
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{
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int r;
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struct sembuf semops[1];
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#if PARANOID
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/* XXX should we check whether the value is already 0 ? */
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SM_REQUIRE(sm_get_sem(semid, semnum) > 0);
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#endif /* PARANOID */
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semops[0].sem_num = semnum;
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semops[0].sem_op = 1;
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semops[0].sem_flg = SEM_UNDO |
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(timeout != SM_TIME_FOREVER ? 0 : IPC_NOWAIT);
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if (timeout == SM_TIME_IMMEDIATE || timeout == SM_TIME_FOREVER)
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return semop(semid, semops, 1);
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do
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{
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r = semop(semid, semops, 1);
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if (r == 0)
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return r;
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sleep(1);
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--timeout;
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} while (timeout > 0);
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return r;
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}
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/*
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** SM_SEM_GET -- get semaphore value.
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**
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** Parameters:
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** semid -- id for semaphores.
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** semnum -- number of semaphore.
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**
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** Returns:
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** value of semaphore on success.
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** < 0 on failure.
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*/
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int
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sm_sem_get(semid, semnum)
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int semid;
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int semnum;
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{
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int semval;
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if ((semval = semctl(semid, semnum, GETVAL, NULL)) < 0)
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return -1;
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return semval;
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}
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#endif /* SM_CONF_SEM */
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