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lock.c
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lock.c
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/*
* Copyright (C) 2001-2003 FhG Fokus
*
* This file is part of Kamailio, a free SIP server.
*
* Kamailio is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version
*
* Kamailio is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "defs.h"
#include <errno.h>
#include "lock.h"
#include "../../dprint.h"
#ifndef GEN_LOCK_T_PREFERED
/* semaphore probing limits */
#define SEM_MIN 16
#define SEM_MAX 4096
/* we implement mutex here using lock sets; as the number of
semaphores may be limited (e.g. sysv) and number of synchronized
elements high, we partition the synced SER elements and share
semaphores in each of the partitions; we try to use as many
semaphores as OS gives us for finest granularity.
we allocate the locks according to the following plans:
1) we allocate a semaphore set for hash_entries and
try to use as many semaphores in it as OS allows;
we partition the hash_entries by available
semaphores which are shared in each partition
2) cells get always the same semaphore as its hash
entry in which they live
*/
/* and the maximum number of semaphores in the entry_semaphore set */
static int sem_nr;
gen_lock_set_t* entry_semaphore=0;
gen_lock_set_t* reply_semaphore=0;
gen_lock_set_t* async_semaphore=0;
#endif
/* initialize the locks; return 0 on success, -1 otherwise
*/
int lock_initialize()
{
#ifndef GEN_LOCK_T_PREFERED
int i;
int probe_run;
#endif
/* first try allocating semaphore sets with fixed number of semaphores */
DBG("DEBUG: lock_initialize: lock initialization started\n");
#ifndef GEN_LOCK_T_PREFERED
i=SEM_MIN;
/* probing phase: 0=initial, 1=after the first failure */
probe_run=0;
again:
do {
if (entry_semaphore!=0){ /* clean-up previous attempt */
lock_set_destroy(entry_semaphore);
lock_set_dealloc(entry_semaphore);
}
if (reply_semaphore!=0){
lock_set_destroy(reply_semaphore);
lock_set_dealloc(reply_semaphore);
}
if (async_semaphore!=0){
lock_set_destroy(async_semaphore);
lock_set_dealloc(async_semaphore);
}
if (i==0){
LOG(L_CRIT, "lock_initialize: could not allocate semaphore"
" sets\n");
goto error;
}
if (((entry_semaphore=lock_set_alloc(i))==0)||
(lock_set_init(entry_semaphore)==0)) {
DBG("DEBUG: lock_initialize: entry semaphore "
"initialization failure: %s\n", strerror( errno ) );
if (entry_semaphore){
lock_set_dealloc(entry_semaphore);
entry_semaphore=0;
}
/* first time: step back and try again */
if (probe_run==0) {
DBG("DEBUG: lock_initialize: first time "
"semaphore allocation failure\n");
i--;
probe_run=1;
continue;
/* failure after we stepped back; give up */
} else {
DBG("DEBUG: lock_initialize: second time semaphore"
" allocation failure\n");
goto error;
}
}
/* allocation succeeded */
if (probe_run==1) { /* if ok after we stepped back, we're done */
break;
} else { /* if ok otherwise, try again with larger set */
if (i==SEM_MAX) break;
else {
i++;
continue;
}
}
} while(1);
sem_nr=i;
if (((reply_semaphore=lock_set_alloc(i))==0)||
(lock_set_init(reply_semaphore)==0)){
if (reply_semaphore){
lock_set_dealloc(reply_semaphore);
reply_semaphore=0;
}
DBG("DEBUG:lock_initialize: reply semaphore initialization"
" failure: %s\n", strerror(errno));
probe_run=1;
i--;
goto again;
}
i++;
if (((async_semaphore=lock_set_alloc(i))==0)||
(lock_set_init(async_semaphore)==0)){
if (async_semaphore){
lock_set_dealloc(async_semaphore);
async_semaphore=0;
}
DBG("DEBUG:lock_initialize: async semaphore initialization"
" failure: %s\n", strerror(errno));
probe_run=1;
i--;
goto again;
}
/* return success */
LOG(L_INFO, "INFO: semaphore arrays of size %d allocated\n", sem_nr );
#endif /* GEN_LOCK_T_PREFERED*/
return 0;
#ifndef GEN_LOCK_T_PREFERED
error:
lock_cleanup();
return -1;
#endif
}
#ifdef GEN_LOCK_T_PREFERED
void lock_cleanup()
{
/* must check if someone uses them, for now just leave them allocated*/
}
#else
/* remove the semaphore set from system */
void lock_cleanup()
{
/* that's system-wide; all other processes trying to use
the semaphore will fail! call only if it is for sure
no other process lives
*/
/* sibling double-check missing here; install a signal handler */
if (entry_semaphore !=0){
lock_set_destroy(entry_semaphore);
lock_set_dealloc(entry_semaphore);
};
if (reply_semaphore !=0) {
lock_set_destroy(reply_semaphore);
lock_set_dealloc(reply_semaphore);
};
if (async_semaphore !=0) {
lock_set_destroy(async_semaphore);
lock_set_dealloc(async_semaphore);
};
entry_semaphore = reply_semaphore = async_semaphore = 0;
}
#endif /*GEN_LOCK_T_PREFERED*/
int init_cell_lock( struct cell *cell )
{
#ifdef GEN_LOCK_T_PREFERED
lock_init(&cell->reply_mutex);
#else
cell->reply_mutex.semaphore_set=reply_semaphore;
cell->reply_mutex.semaphore_index = cell->hash_index % sem_nr;
#endif /* GEN_LOCK_T_PREFERED */
return 0;
}
int init_entry_lock( struct s_table* ht, struct entry *entry )
{
#ifdef GEN_LOCK_T_PREFERED
lock_init(&entry->mutex);
#else
/* just advice which of the available semaphores to use;
specifically, all entries are partitioned into as
many partitions as number of available semaphores allows
*/
entry->mutex.semaphore_set=entry_semaphore;
entry->mutex.semaphore_index = ( ((char *)entry - (char *)(ht->entries ) )
/ sizeof(struct entry) ) % sem_nr;
#endif
return 0;
}
int init_async_lock( struct cell *cell )
{
#ifdef GEN_LOCK_T_PREFERED
lock_init(&cell->async_mutex);
#else
cell->async_mutex.semaphore_set=async_semaphore;
cell->async_mutex.semaphore_index = cell->hash_index % sem_nr;
#endif /* GEN_LOCK_T_PREFERED */
return 0;
}
int release_cell_lock( struct cell *cell )
{
#ifndef GEN_LOCK_T_PREFERED
/* don't do anything here -- the init_*_lock procedures
just advised on usage of shared semaphores but did not
generate them
*/
#endif
return 0;
}
int release_entry_lock( struct entry *entry )
{
/* the same as above */
return 0;
}