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/* Copyright (c) 1996-2004, Adaptec Corporation
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* - Neither the name of the Adaptec Corporation nor the names of its
* contributors may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
//File - SEMAPHOR.C
//***************************************************************************
//
//Description:
//
// This file contains function definitions to work with mutually
//exclusive semaphors in an OS independent manner.
//
//Author:
//Date:
//
//Editors:
//
//Remarks:
//
// NOTE NOTE!
//
// The method of using file read and write locks to know if you are the
// only one who has the semaphore open will not work if multiple threads
// in a single process open the same named semaphore. This is because a
// file lock is per process not per thread. So, one thread could change
// another thread's read lock to a write lock and not know it.
//
// Currently at DPT, threads share the same semaphore handle, so it is
// not a problem.
//
//***************************************************************************
/* Include Files ------------------------------------------------------------*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <signal.h>
#include "osd_util.h"
/*
* Some Unixes require a fourth parameter to semctl of type 'union semun',
* while other variants are more flexible but also don't define that type.
*
* To make matters even more interesting, SCO UNIX 3.2.4.2 defines it, but SCO
* OpenServer doesn't. Since we still need to support 3.2.4.2, if compiling
* on OpenServer add -D_DPT_DEFINE_SEMUN=1 to your makefile.
*
* Also, for new operating systems, it is preferrable to add the above define
* in your makefile rather than add the OS-define below in the code.
*/
#if !defined(_DPT_DEFINE_SEMUN)
#if defined(_DPT_FREE_BSD) || defined(_DPT_BSDI)
#define _DPT_DEFINE_SEMUN 0
#else
#define _DPT_DEFINE_SEMUN 1
#endif
#endif
/* Definitions - Defines & Constants ----------------------------------------*/
#define MAX_LOCAL_SEM 10
#define MAX_SEM_NAME_LEN 80 /* including 5 characters added here "/tmp/" */
/* Definitions - Structures -------------------------------------------------*/
typedef struct {
char semName[MAX_SEM_NAME_LEN];
int handle;
int semID;
int index;
} DPT_Semaphore_S;
#if _DPT_DEFINE_SEMUN != 0
union semun {
int val;
};
#endif
/* Global Variables ---------------------------------------------------------*/
static char LocalSemaphoreName[MAX_SEM_NAME_LEN] = "";
static int LocalSemaphoreInUse[MAX_LOCAL_SEM];
static int LocalSemID = -1;
extern int Verbose;
/* Function Prototypes ------------------------------------------------------*/
//Function - privateCreateNamedSemaphore() - start
//===========================================================================
//
//Description:
//
// This function creates a semaphore to provide mutually exclusive
//or event-type access to an application resource.
//
//Parameters:
//
//Return Value:
//
// NULL = Failure, unable to create a new semaphore
// Non-zero = Success, handle to the newly created semaphore
//
//Remarks: (Side effects, Assumptions, Warnings...)
//
// A helper function for other routines in this file. It is internal to
// this file and should not be called from outside.
//
//---------------------------------------------------------------------------
static SEMAPHORE_T privateCreateNamedSemaphore(char *name, int initialValue)
{
DPT_Semaphore_S *rtnVal;
int iAmFirst = 0;
key_t key;
union semun arg;
struct flock lock;
rtnVal = (DPT_Semaphore_S *) malloc(sizeof(DPT_Semaphore_S));
if (rtnVal != NULL) {
// Open the file so we can get file lock on it and create if it
// doesn't exist
rtnVal->handle = open(name, O_CREAT | O_RDWR, S_IRWXU | S_IRWXG);
if (rtnVal->handle < 0) {
free(rtnVal);
rtnVal = NULL;
}
}
if (rtnVal != NULL) {
strcpy(rtnVal->semName, name);
rtnVal->index = 0;
// See if anyone else is using the semaphore. If anyone else is using
// it, they will have a read lock and I wouldn't be able to get the
// write lock without waiting. If someone else is using it, wait for
// them and get a read lock. If I exit this code block without error,
// I'll have some kind of lock
lock.l_type = F_WRLCK;
lock.l_whence = SEEK_SET;
lock.l_start = 0;
lock.l_len = 0; // till end-of-file
if (fcntl(rtnVal->handle, F_SETLK, &lock) != 0) {
if (errno != EACCES && errno != EAGAIN) {
close(rtnVal->handle);
free(rtnVal);
rtnVal = NULL;
} else {
// Let others know I'm using the semaphore
lock.l_type = F_RDLCK;
if (fcntl(rtnVal->handle, F_SETLKW, &lock) != 0) {
close(rtnVal->handle);
free(rtnVal);
rtnVal = NULL;
}
}
} else {
iAmFirst = 1;
}
}
lock.l_type = F_UNLCK; // if anything goes wrong I need to unlock
if (rtnVal != NULL) {
// Get the key for the file to use to get the actual semaphore
key = ftok(rtnVal->semName, 'D');
if (key == (key_t) -1) {
fcntl(rtnVal->handle, F_SETLKW, &lock);
close(rtnVal->handle);
free(rtnVal);
rtnVal = NULL;
}
}
if (rtnVal != NULL) {
// Get the semaphore handle and create it if it isn't already there.
// Let other processes access it as well
rtnVal->semID = semget(key, 1, IPC_CREAT | S_IRWXU | S_IRWXG);
if (rtnVal->semID == -1) {
if (Verbose)
perror("\nprivateCreateNamedSemaphore");
fcntl(rtnVal->handle, F_SETLKW, &lock);
close(rtnVal->handle);
free(rtnVal);
rtnVal = NULL;
}
}
// At this point, if we are the first (and only) person to get the
// semaphore, initialize its start value
if (rtnVal != NULL && iAmFirst) {
arg.val = initialValue;
if (semctl(rtnVal->semID, rtnVal->index, SETVAL, arg) != 0) {
// note arg is unused for IPC_RMID
semctl(rtnVal->semID, 0, IPC_RMID, arg);
fcntl(rtnVal->handle, F_SETLKW, &lock);
close(rtnVal->handle);
free(rtnVal);
rtnVal = NULL;
} else {
// Release the Write lock and change to a read lock
lock.l_type = F_RDLCK;
if (fcntl(rtnVal->handle, F_SETLK, &lock) != 0) {
// note arg is unused for IPC_RMID
semctl(rtnVal->semID, 0, IPC_RMID, arg);
close(rtnVal->handle);
free(rtnVal);
rtnVal = NULL;
}
}
}
return((SEMAPHORE_T) rtnVal);
}
//privateCreateNamedSemaphore() - end
//Function - privateCreateUnnamedSemaphore() - start
//===========================================================================
//
//Description:
//
// This function creates a semaphore to provide mutually exclusive
//or event-type access to an application resource.
//
//Parameters:
//
//Return Value:
//
// NULL = Failure, unable to create a new semaphore
// Non-zero = Success, handle to the newly created semaphore
//
//Remarks: (Side effects, Assumptions, Warnings...)
//
// A helper function for other routines in this file. It is internal to
// this file and should not be called from outside.
//
//---------------------------------------------------------------------------
static SEMAPHORE_T privateCreateUnnamedSemaphore(int initialValue)
{
DPT_Semaphore_S *rtnVal;
union semun arg;
int i;
if (LocalSemID == -1) {
// If we can't get the program name or create the file, go with the
// private semaphore instead of a key based on ftok()
key_t key = IPC_PRIVATE;
if (LocalSemaphoreName[0] == '\0') {
extern char **Argv;
char *name;
int handle;
name = Argv[0];
if (name != NULL) {
name = strrchr(name, '/');
if (name != NULL)
name++;
else
name = Argv[0];
}
if (name != NULL) {
strcpy(LocalSemaphoreName, "/tmp/");
strcat(LocalSemaphoreName, name);
strcat(LocalSemaphoreName,"_unnamed");
handle = open(LocalSemaphoreName, O_CREAT | O_RDWR, 0);
if (handle < 0)
LocalSemaphoreName[0] = '\0';
else {
close(handle);
key = ftok(LocalSemaphoreName, 'D');
if (key == (key_t) -1) {
LocalSemaphoreName[0] = '\0';
key = IPC_PRIVATE;
}
}
}
}
// Get the semaphore ID for the block of unnamed semaphores
LocalSemID = semget(key, MAX_LOCAL_SEM, IPC_CREAT);
if (LocalSemID == -1) {
if (Verbose)
perror("\nprivateCreateUnnamedSemaphore");
return NULL;
}
for (i = 0; i < MAX_LOCAL_SEM; i++)
LocalSemaphoreInUse[i] = 0;
}
for (i = 0; i < MAX_LOCAL_SEM && LocalSemaphoreInUse[i]; i++) {
// Nothing
}
if (i == MAX_LOCAL_SEM) {
if (Verbose)
printf("\nToo many unnamed semaphores!");
return NULL;
}
rtnVal = (DPT_Semaphore_S *) malloc(sizeof(DPT_Semaphore_S));
if (rtnVal != NULL) {
LocalSemaphoreInUse[i] = 1;
rtnVal->semName[0] = '\0';
rtnVal->semID = LocalSemID;
rtnVal->handle = -1;
rtnVal->index = i;
}
// Initialize the semaphore's start value
if (rtnVal != NULL) {
arg.val = initialValue;
if (semctl(LocalSemID, rtnVal->index, SETVAL, arg) != 0) {
LocalSemaphoreInUse[rtnVal->index] = 0;
free(rtnVal);
rtnVal = NULL;
}
}
return((SEMAPHORE_T) rtnVal);
}
//privateCreateUnnamedSemaphore() - end
//Function - osdCreateSemaphore() - start
//===========================================================================
//
//Description:
//
// This function creates a semaphore to provide mutually exclusive
//access to an application resource.
//
//Parameters:
//
//Return Value:
//
// NULL = Failure, unable to create a new semaphore
// Non-zero = Success, handle to the newly created semaphore
//
//Remarks: (Side effects, Assumptions, Warnings...)
//
//---------------------------------------------------------------------------
SEMAPHORE_T osdCreateSemaphore()
{
SEMAPHORE_T rtnVal;
rtnVal = privateCreateUnnamedSemaphore(0);
if (Verbose)
printf("\nosdCreateSemaphore : Rtn = %lx", (unsigned long)rtnVal);
return(rtnVal);
}
//osdCreateSemaphore() - end
//Function - osdCreateNamedSemaphore - start
//===========================================================================
//
//Description: creates a named semaphore so outside processes can gain access
// to it
//
//
//Parameters:
//
//Return Value:
//
// NULL = Failure, unable to create a new semaphore
// Non-zero = Success, handle to the newly created semaphore
//
//Global Variables Affected:
//
//Remarks: (Side effects, Assumptions, Warnings...)
//
//
//---------------------------------------------------------------------------
SEMAPHORE_T osdCreateNamedSemaphore(char *name)
{
char temp[MAX_SEM_NAME_LEN];
SEMAPHORE_T rtnVal;
strcpy(temp, "/tmp/");
strcat(temp, name);
rtnVal = privateCreateNamedSemaphore(temp, 0);
if (Verbose)
printf("\nosdCreateNamedSemaphore : Rtn = %lx", (unsigned long)rtnVal);
return(rtnVal);
}
//osdCreateNamedSemaphore() - end
//Function - osdDestroySemaphore() - start
//===========================================================================
//
//Description:
//
// This function destroys the specified mutually exclusive
//semaphore.
//
//Parameters:
//
// semHandle = Handle to the semaphore to be destroyed
//
//Return Value:
//
// 0 = Success, semaphore destroyed
// non-zero = Failure, semaphore not destroyed
//
//Remarks: (Side effects, Assumptions, Warnings...)
//
//---------------------------------------------------------------------------
uSHORT osdDestroySemaphore(SEMAPHORE_T semHandle)
{
DPT_Semaphore_S *sem = (DPT_Semaphore_S *) semHandle;
uSHORT rtnVal = 0;
if (sem->semName[0] == '\0') {
int i;
// It's an unnamed semaphore, set the index in the block to not-in-use
if (sem->index < MAX_LOCAL_SEM)
LocalSemaphoreInUse[sem->index] = 0;
// If all unnamed semaphores are now not-in-use, give back the
// semaphore block
for (i = 0; i < MAX_LOCAL_SEM && !LocalSemaphoreInUse[i]; i++) {
// Nothing
}
if (i == MAX_LOCAL_SEM) {
union semun arg;
// note arg is unused for IPC_RMID
arg.val = 0;
rtnVal = semctl(LocalSemID, 0, IPC_RMID, arg) != 0;
if (rtnVal == 0) {
LocalSemID = -1;
unlink(LocalSemaphoreName);
}
}
} else {
// It's a nammed semaphore
struct flock lock;
// See if anyone else is using the semaphore. If anyone else is using
// it, they will have a read lock and I wouldn't be able to change my
// lock to a write lock without waiting.
lock.l_type = F_WRLCK;
lock.l_whence = SEEK_SET;
lock.l_start = 0;
lock.l_len = 0; // till end-of-file
if (fcntl(sem->handle, F_SETLK, &lock) == 0) {
union semun arg;
// I got the write lock; I must be the last one using the
// semaphore. Delete it and the file associated with it.
// note arg is unused for IPC_RMID
arg.val = 0;
semctl(sem->semID, 0, IPC_RMID, arg);
unlink(sem->semName);
}
else
{
// I didn't get the write lock; someone else has the semaphore
// open. Release my read lock now that I'm not using the
// semaphore any more.
lock.l_type = F_UNLCK;
rtnVal = fcntl(sem->handle, F_SETLKW, &lock) != 0;
}
close(sem->handle);
}
if (rtnVal == 0)
free(sem);
if (Verbose)
printf("\nosdDestroySemaphore : Rtn = %x", rtnVal);
return(rtnVal);
}
//osdDestroySemaphore() - end
//Function - osdRequestSemaphore() - start
//===========================================================================
//
//Description:
//
// This function requests access to the specified mutually
//exclusive semaphore.
//
//Parameters:
//
// semHandle = Handle to the semaphore to request access
// timeout = # of milliseconds to wait for the semaphore
//
//Return Value:
//
// 0 = Access granted
// Non-zero = Access denied (timed out)
//
//Remarks: (Side effects, Assumptions, Warnings...)
//
//---------------------------------------------------------------------------
static void semaphoreSignalHandler(int sig)
{
// do nothing, we'll get an error back from semop()
sig = sig;
}
uLONG osdRequestSemaphore(SEMAPHORE_T semHandle, uLONG timeout)
{
DPT_Semaphore_S *sem = (DPT_Semaphore_S *) semHandle;
uLONG rtnVal = 0;
int resetAction = 0;
unsigned int oldAlarm;
unsigned int waited;
struct sembuf semOps[2];
struct sigaction newSig;
struct sigaction oldSig;
// Set up for two operations on this semaphore. First wait for it to
// go to 0, and then set it to 1
semOps[0].sem_num = sem->index;
semOps[0].sem_op = 0;
semOps[0].sem_flg = 0;
semOps[1].sem_num = sem->index;
semOps[1].sem_op = 1;
semOps[1].sem_flg = 0;
// If they don't want to wait, set the appropriate flag and change the
// timeout variable as a signal to code below not to set an alarm
if (timeout == 0) {
semOps[0].sem_flg |= IPC_NOWAIT;
semOps[1].sem_flg |= IPC_NOWAIT;
timeout = 0xffffffff;
}
// Set up an alarm signal to timeout our semop() call unless the user
// asked for an "infinite" timeout by sending FFFFFFFF or we are asked
// not to wait at all.
//
// Remember how much time was remaining on old Alarm, if any, and reset
// signal handler to point to ours for the duration of our wait. Then
// set an alarm for our timeout.
//
if (timeout != 0xffffffff)
{
// Convert timeout to seconds and round up
timeout = (timeout + 999) / 1000;
memset(&newSig, 0, sizeof(newSig));
newSig.sa_handler = semaphoreSignalHandler;
oldAlarm = alarm(0);
rtnVal = (sigaction (SIGALRM, &newSig, &oldSig) != 0);
if (rtnVal == 0) {
resetAction = 1;
alarm((unsigned int) timeout);
} else {
// try to set back to their original alarm value remaining
alarm(oldAlarm);
}
}
// Now wait for the semaphore
if (rtnVal == 0) {
rtnVal = (semop(sem->semID, semOps, 2) != 0);
}
// If we set an alarm above, adjust things
if (timeout != 0xffffffff) {
// Calculate how much time we were waiting and if necessary, restart
// the Alarm for the remaining time from the caller's original alarm.
// If we waited longer than they had remaining when we started, raise
// the signal after replacing their handler so they'll get it
// immediately
waited = (unsigned int) timeout - alarm(0);
if (resetAction) {
sigaction (SIGALRM, &oldSig, NULL);
}
if (oldAlarm != 0) {
if (oldAlarm > waited) {
alarm(oldAlarm - waited);
} else {
raise(SIGALRM);
}
}
}
if (Verbose)
printf("\nosdRequestSemaphore : Rtn = %lx\n", rtnVal);
return(rtnVal);
}
//osdRequestSemaphore() - end
//Function - osdReleaseSemaphore() - start
//===========================================================================
//
//Description:
//
// This function relinquishes control of the specified mutually
//exclusive semaphore.
//
//Parameters:
//
// semHandle = Handle to the semaphore to be released.
//
//Return Value:
//
// 0 = Success, the semaphore has been released
// Non-zero = Failure, unable to release the semaphore
//
//Remarks: (Side effects, Assumptions, Warnings...)
//
//---------------------------------------------------------------------------
uSHORT osdReleaseSemaphore(SEMAPHORE_T semHandle)
{
DPT_Semaphore_S *sem = (DPT_Semaphore_S *) semHandle;
uSHORT rtnVal = 1;
struct sembuf semOp;
// Set Up To Decrement The Semaphore Value By 1
semOp.sem_num = sem->index;
semOp.sem_op = -1;
semOp.sem_flg = IPC_NOWAIT;
rtnVal = semop(sem->semID, &semOp, 1) != 0;
if (rtnVal && errno == EAGAIN) {
// Ignore errors caused by releasing the semaphore too many times.
// This can happen legitimately through osdSignalEventSemaphore().
rtnVal = 0;
}
if (Verbose)
printf("\nosdReleaseSemaphore : Rtn = %x\n", rtnVal);
return(rtnVal);
}
//osdReleaseSemaphore() - end
//Function - osdResetEventSemaphore - start
//===========================================================================
//
//Description: resets the event to the unhappened state
//
//
//
//Parameters:
//
//Return Value:
//
//Global Variables Affected:
//
//Remarks: (Side effects, Assumptions, Warnings...)
//
//
//---------------------------------------------------------------------------
uLONG osdResetEventSemaphore(SEMAPHORE_T semHandle)
{
semHandle = semHandle;
return 0;
}
//osdResetEventSemaphore() - end
//Function - osdSignalEventSemaphore - start
//===========================================================================
//
//Description: set this event to happened
//
//
//
//Parameters:
//
//Return Value:
//
//Global Variables Affected:
//
//Remarks: (Side effects, Assumptions, Warnings...)
//
//
//---------------------------------------------------------------------------
uLONG osdSignalEventSemaphore(SEMAPHORE_T semHandle)
{
return (uLONG) osdReleaseSemaphore(semHandle);
}
//osdSignalEventSemaphore() - end
//Function - osdWaitForEventSemaphore - start
//===========================================================================
//
//Description: waits for an event semaphore to be signaled either forever
// or until the number of milliseconds has expired
//
//
//
//Parameters:
//
//Return Value: 0 success
//
//Global Variables Affected:
//
//Remarks: (Side effects, Assumptions, Warnings...)
//
//
//---------------------------------------------------------------------------
uLONG osdWaitForEventSemaphore(SEMAPHORE_T semHandle, uLONG timeout)
{
return osdRequestSemaphore(semHandle, timeout);
}
//osdWaitForEventSemaphore() - end
//Function - osdCreateEventSemaphore() - start
//===========================================================================
//
//Description:
//
// This function creates an event semaphore to allow synchronization between
// threads
//
//
//Parameters:
//
//Return Value:
//
// NULL = Failure, unable to create a new semaphore
// Non-zero = Success, handle to the newly created semaphore
//
//Remarks: (Side effects, Assumptions, Warnings...)
//
//---------------------------------------------------------------------------
SEMAPHORE_T osdCreateEventSemaphore()
{
SEMAPHORE_T rtnVal;
rtnVal = privateCreateUnnamedSemaphore(1);
if (Verbose)
printf("\nosdCreateEventSemaphore : Rtn = %lx", (unsigned long)rtnVal);
return(rtnVal);
}
//osdCreateEventSemaphore() - end
//Function - osdCreateNamedEventSemaphore - start
//===========================================================================
//
// This function creates a named event semaphore to allow synchronization
// between threads and processes
//
//
//Parameters:
//
//Return Value:
//
//Global Variables Affected:
//
//Remarks: (Side effects, Assumptions, Warnings...)
//
//
//---------------------------------------------------------------------------
SEMAPHORE_T osdCreateNamedEventSemaphore(char *name)
{
char temp[MAX_SEM_NAME_LEN];
SEMAPHORE_T rtnVal;
strcpy(temp, "/tmp/");
strcat(temp, name);
rtnVal = privateCreateNamedSemaphore(temp, 1);
if (Verbose)
printf("\nosdCreateNamedEventSemaphore : Rtn = %lx", (unsigned long)rtnVal);
return(rtnVal);
}
//osdCreateNamedEventSemaphore() - end
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