lock_ops.h

/* $Id$ */
/*
 *
 * Copyright (C) 2001-2003 FhG Fokus
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 *   ser locking library
 *   WARNING: do not include this file directly, use instead locking.h
 *   (unless you don't need to alloc/dealloc locks)
 *
 *  2002-12-16  created by andrei
 *  2003-02-20  s/gen_lock_t/gen_lock_t/ to avoid a type conflict 
 *               on solaris  (andrei)
 *  2003-03-05  lock set support added for FAST_LOCK & SYSV (andrei)
 *  2003-03-06  removed *_alloc,*_dealloc & moved them to lock_alloc.h
 *              renamed locking.h to lock_ops.h (all this to solve
 *              the locking.h<->shm_mem.h interdependency) (andrei)
 *  2003-03-10  lock set support added also for PTHREAD_MUTEX & POSIX_SEM
 *               (andrei)
 *  2003-03-17  possible signal interruptions treated for sysv (andrei)
 *  2004-07-28  s/lock_set_t/gen_lock_set_t/ because of a type conflict
 *              on darwin (andrei)
 *  2006-04-04  added lock_try(lock) and lock_set_try(s,i) (andrei)
 *  2007-05-13  added futex support (andrei)
 *
Implements:

        simple locks:
        -------------
        gen_lock_t* lock_init(gen_lock_t* lock); - inits the lock
        void    lock_destroy(gen_lock_t* lock);  - removes the lock (e.g sysv rmid)
        void    lock_get(gen_lock_t* lock);      - lock (mutex down)
        void    lock_release(gen_lock_t* lock);  - unlock (mutex up)
        int     lock_try(gen_lock_t* lock);      - tries to get the lock, returns
                                                    0 on success and !=0 on failure
        
        lock sets: 
        ----------
        gen_lock_set_t* lock_set_init(gen_lock_set_t* set);  - inits the lock set
        void lock_set_destroy(gen_lock_set_t* s);        - removes the lock set
        void lock_set_get(gen_lock_set_t* s, int i);     - locks sem i from the set
        void lock_set_release(gen_lock_set_t* s, int i)  - unlocks sem i from the
                                                           set
        int  lock_set_try(gen_lock_set_t* s, int i);    - tries to lock the sem i,
                                                          returns 0 on success and
                                                          !=0 on failure
        
        defines:
        --------
        GEN_LOCK_T_PREFERRED - defined if using  arrays of gen_lock_t is as good as
                              using a lock set (gen_lock_set_t). 
                                                  In general is better to have the locks "close" or 
                                                  inside the protected data structure rather then 
                                                  having a separate array or lock set. However in some
                                                  case (e.g. SYSV_LOCKS) is better to use lock sets,
                                                  either due to lock number limitations, excesive 
                                                  performance or memory overhead. In this cases
                                                  GEN_LOCK_T_PREFERRED will not be defined.
        GEN_LOCK_T_UNLIMITED - defined if there is no system imposed limit on
                               the number of locks (other then the memory).
        GEN_LOCK_SET_T_UNLIMITED
                              - like above but for the size of a lock set.

WARNING: - lock_set_init may fail for large number of sems (e.g. sysv). 
         - signals are not treated! (some locks are "awakened" by the signals)
*/

#ifndef _lock_ops_h
#define _lock_ops_h

#ifdef USE_FUTEX
#include "futexlock.h"
/* if no native atomic ops support => USE_FUTEX will be undefined */
#endif


#ifdef USE_FUTEX

typedef futex_lock_t gen_lock_t;

#define lock_destroy(lock) /* do nothing */
#define lock_init(lock) futex_init(lock)
#define lock_try(lock)  futex_try(lock)
#define lock_get(lock)  futex_get(lock)
#define lock_release(lock) futex_release(lock)


#elif defined FAST_LOCK
#include "fastlock.h"

typedef fl_lock_t gen_lock_t;


#define lock_destroy(lock) /* do nothing */ 

inline static gen_lock_t* lock_init(gen_lock_t* lock)
{
        init_lock(*lock);
        return lock;
}

#define lock_try(lock) try_lock(lock)
#define lock_get(lock) get_lock(lock)
#define lock_release(lock) release_lock(lock)


#elif defined USE_PTHREAD_MUTEX
#include <pthread.h>

typedef pthread_mutex_t gen_lock_t;

#define lock_destroy(lock) /* do nothing */ 

inline static gen_lock_t* lock_init(gen_lock_t* lock)
{
        if (pthread_mutex_init(lock, 0)==0) return lock;
        else return 0;
}

#define lock_try(lock) pthread_mutex_trylock(lock)
#define lock_get(lock) pthread_mutex_lock(lock)
#define lock_release(lock) pthread_mutex_unlock(lock)



#elif defined USE_POSIX_SEM
#include <semaphore.h>

typedef sem_t gen_lock_t;

#define lock_destroy(lock) /* do nothing */ 

inline static gen_lock_t* lock_init(gen_lock_t* lock)
{
        if (sem_init(lock, 1, 1)<0) return 0;
        return lock;
}

#define lock_try(lock) sem_trywait(lock)
#define lock_get(lock) sem_wait(lock)
#define lock_release(lock) sem_post(lock)


#elif defined USE_SYSV_SEM
#include <sys/ipc.h>
#include <sys/sem.h>

#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include "dprint.h"
#include "globals.h" /* uid */

#if ((defined(HAVE_UNION_SEMUN) || defined(__GNU_LIBRARY__) )&& !defined(_SEM_SEMUN_UNDEFINED)) 
        
        /* union semun is defined by including sem.h */
#else
        /* according to X/OPEN we have to define it ourselves */
        union semun {
                int val;                      /* value for SETVAL */
                struct semid_ds *buf;         /* buffer for IPC_STAT, IPC_SET */
                unsigned short int *array;    /* array for GETALL, SETALL */
                struct seminfo *__buf;        /* buffer for IPC_INFO */
        };
#endif

typedef int gen_lock_t;




inline static gen_lock_t* lock_init(gen_lock_t* lock)
{
        union semun su;
        int euid;
        
        euid=geteuid();
        if (uid && uid!=euid)
                seteuid(uid); /* set euid to the cfg. requested one */
        *lock=semget(IPC_PRIVATE, 1, 0700);
        if (uid && uid!=euid)
                seteuid(euid); /* restore it */
        if (*lock==-1) return 0;
        su.val=1;
        if (semctl(*lock, 0, SETVAL, su)==-1){
                /* init error*/
                return 0;
        }
        return lock;
}

inline static void lock_destroy(gen_lock_t* lock)
{
        semctl(*lock, 0, IPC_RMID, (union semun)(int)0);
}


/* returns 0 if it got the lock, -1 otherwise */
inline static int lock_try(gen_lock_t* lock)
{
        struct sembuf sop;

        sop.sem_num=0;
        sop.sem_op=-1; /* down */
        sop.sem_flg=IPC_NOWAIT; 
tryagain:
        if (semop(*lock, &sop, 1)==-1){
                if (errno==EAGAIN){
                        return -1;
                }else if (errno==EINTR){
                        DBG("lock_get: signal received while waiting for on a mutex\n");
                        goto tryagain;
                }else{
                        LOG(L_CRIT, "ERROR: lock_get sysv: %s (%d)\n", strerror(errno),
                                                errno);
                        return -1;
                }
        }
        return 0;
}

inline static void lock_get(gen_lock_t* lock)
{
        struct sembuf sop;

        sop.sem_num=0;
        sop.sem_op=-1; /* down */
        sop.sem_flg=0; 
tryagain:
        if (semop(*lock, &sop, 1)==-1){
                if (errno==EINTR){
                        DBG("lock_get: signal received while waiting for on a mutex\n");
                        goto tryagain;
                }else{
                        LOG(L_CRIT, "ERROR: lock_get sysv: %s (%d)\n", strerror(errno),
                                                errno);
                }
        }
}

inline static void lock_release(gen_lock_t* lock)
{
        struct sembuf sop;
        
        sop.sem_num=0;
        sop.sem_op=1; /* up */
        sop.sem_flg=0; 
tryagain:
        if (semop(*lock, &sop, 1)==-1){
                if (errno==EINTR){
                        /* very improbable*/
                        DBG("lock_release: signal received while releasing a mutex\n");
                        goto tryagain;
                }else{
                        LOG(L_CRIT, "ERROR: lock_release sysv: %s (%d)\n",
                                        strerror(errno), errno);
                }
        }
}


#else
#error "no locking method selected"
#endif


/* lock sets */

#if defined(FAST_LOCK) || defined(USE_PTHREAD_MUTEX) || \
        defined(USE_POSIX_SEM) || defined(USE_FUTEX)
#define GEN_LOCK_T_PREFERRED
#define GEN_LOCK_T_PREFERED  /* backwards compat. */
#define GEN_LOCK_T_UNLIMITED
#define GEN_LOCK_SET_T_UNLIMITED

struct gen_lock_set_t_ {
        long size;
        gen_lock_t* locks;
}; /* must be  aligned (32 bits or 64 depending on the arch)*/
typedef struct gen_lock_set_t_ gen_lock_set_t;


#define lock_set_destroy(lock_set) /* do nothing */

inline static gen_lock_set_t* lock_set_init(gen_lock_set_t* s)
{
        int r;
        for (r=0; r<s->size; r++) if (lock_init(&s->locks[r])==0) return 0;
        return s;
}

/* WARNING: no boundary checks!*/
#define lock_set_try(set, i) lock_try(&set->locks[i])
#define lock_set_get(set, i) lock_get(&set->locks[i])
#define lock_set_release(set, i) lock_release(&set->locks[i])

#elif defined(USE_SYSV_SEM)
#undef GEN_LOCK_T_PREFERRED
#undef GEN_LOCK_T_PREFERED  /* backwards compat. */
#undef GEN_LOCK_T_UNLIMITED
#undef GEN_LOCK_SET_T_UNLIMITED
#define GEN_LOCK_T_LIMITED
#define GEN_LOCK_SET_T_LIMITED

struct gen_lock_set_t_ {
        int size;
        int semid;
};


typedef struct gen_lock_set_t_ gen_lock_set_t;
inline static gen_lock_set_t* lock_set_init(gen_lock_set_t* s)
{
        union semun su;
        int r;
        int euid;

        euid=geteuid();
        if (uid && uid!=euid)
                seteuid(uid); /* set euid to the cfg. requested one */
        s->semid=semget(IPC_PRIVATE, s->size, 0700);
        if (uid && uid!=euid)
                seteuid(euid); /* restore euid */
        if (s->semid==-1){
                LOG(L_CRIT, "ERROR: lock_set_init (SYSV): semget (..., %d, 0700)"
                                " failed: %s\n",
                                s->size, strerror(errno));
                return 0;
        }
        su.val=1;
        for (r=0; r<s->size; r++){
                if (semctl(s->semid, r, SETVAL, su)==-1){
                        LOG(L_CRIT, "ERROR: lock_set_init (SYSV): semctl failed on sem %d"
                                        ": %s\n", r, strerror(errno));
                        semctl(s->semid, 0, IPC_RMID, (union semun)(int)0);
                        return 0;
                }
        }
        return s;
}

inline static void lock_set_destroy(gen_lock_set_t* s)
{
        semctl(s->semid, 0, IPC_RMID, (union semun)(int)0);
}


/* returns 0 if it "gets" the lock, -1 otherwise */
inline static int lock_set_try(gen_lock_set_t* s, int n)
{
        struct sembuf sop;
        
        sop.sem_num=n;
        sop.sem_op=-1; /* down */
        sop.sem_flg=IPC_NOWAIT; 
tryagain:
        if (semop(s->semid, &sop, 1)==-1){
                if (errno==EAGAIN){
                        return -1;
                }else if (errno==EINTR){
                        DBG("lock_get: signal received while waiting for on a mutex\n");
                        goto tryagain;
                }else{
                        LOG(L_CRIT, "ERROR: lock_get sysv: %s (%d)\n", strerror(errno),
                                                errno);
                        return -1;
                }
        }
        return 0;
}


inline static void lock_set_get(gen_lock_set_t* s, int n)
{
        struct sembuf sop;
        sop.sem_num=n;
        sop.sem_op=-1; /* down */
        sop.sem_flg=0;
tryagain:
        if (semop(s->semid, &sop, 1)==-1){
                if (errno==EINTR){
                        DBG("lock_set_get: signal received while waiting on a mutex\n");
                        goto tryagain;
                }else{
                        LOG(L_CRIT, "ERROR: lock_set_get sysv: %s (%d)\n",
                                        strerror(errno), errno);
                }
        }
}

inline static void lock_set_release(gen_lock_set_t* s, int n)
{
        struct sembuf sop;
        sop.sem_num=n;
        sop.sem_op=1; /* up */
        sop.sem_flg=0;
tryagain:
        if (semop(s->semid, &sop, 1)==-1){
                if (errno==EINTR){
                        /* very improbable */
                        DBG("lock_set_release: signal received while releasing mutex\n");
                        goto tryagain;
                }else{
                        LOG(L_CRIT, "ERROR: lock_set_release sysv: %s (%d)\n",
                                        strerror(errno), errno);
                }
        }
}
#else 
#error "no lock set method selected"
#endif


#endif