mirror of
https://git.openldap.org/openldap/openldap.git
synced 2024-12-21 03:10:25 +08:00
389 lines
8.8 KiB
C
389 lines
8.8 KiB
C
/* $OpenLDAP$ */
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/*
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** This is an improved implementation of Reader/Writer locks does
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** not protect writers from starvation. That is, if a writer is
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** currently waiting on a reader, any new reader will get
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** the lock before the writer.
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**
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** Does not support cancellation nor does any status checking.
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*/
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/* Adapted from publically available examples for:
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* "Programming with Posix Threads"
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* by David R Butenhof, Addison-Wesley
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* http://cseng.aw.com/bookpage.taf?ISBN=0-201-63392-2
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*/
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#include "portable.h"
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#include <ac/stdlib.h>
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#include <ac/errno.h>
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#include <ac/string.h>
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#include <ac/time.h>
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#include "ldap-int.h"
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#include "ldap_pvt_thread.h"
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/*
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* implementations that provide their own compatible
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* reader/writer locks define LDAP_THREAD_HAVE_RDWR
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* in ldap_pvt_thread.h
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*/
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#ifndef LDAP_THREAD_HAVE_RDWR
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struct ldap_int_thread_rdwr_s {
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ldap_pvt_thread_mutex_t ltrw_mutex;
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ldap_pvt_thread_cond_t ltrw_read; /* wait for read */
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ldap_pvt_thread_cond_t ltrw_write; /* wait for write */
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int ltrw_valid;
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#define LDAP_PVT_THREAD_RDWR_VALID 0x0bad
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int ltrw_r_active;
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int ltrw_w_active;
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int ltrw_r_wait;
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int ltrw_w_wait;
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};
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int
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ldap_pvt_thread_rdwr_init( ldap_pvt_thread_rdwr_t *rwlock )
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{
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struct ldap_int_thread_rdwr_s *rw;
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assert( rwlock != NULL );
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rw = (struct ldap_int_thread_rdwr_s *) LDAP_CALLOC( 1,
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sizeof( struct ldap_int_thread_rdwr_s ) );
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/* we should check return results */
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ldap_pvt_thread_mutex_init( &rw->ltrw_mutex );
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ldap_pvt_thread_cond_init( &rw->ltrw_read );
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ldap_pvt_thread_cond_init( &rw->ltrw_write );
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rw->ltrw_valid = LDAP_PVT_THREAD_RDWR_VALID;
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*rwlock = rw;
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return 0;
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}
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int
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ldap_pvt_thread_rdwr_destroy( ldap_pvt_thread_rdwr_t *rwlock )
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{
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struct ldap_int_thread_rdwr_s *rw;
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assert( rwlock != NULL );
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rw = *rwlock;
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assert( rw != NULL );
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assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
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if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
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return LDAP_PVT_THREAD_EINVAL;
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ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
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assert( rw->ltrw_w_active >= 0 );
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assert( rw->ltrw_w_wait >= 0 );
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assert( rw->ltrw_r_active >= 0 );
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assert( rw->ltrw_r_wait >= 0 );
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/* active threads? */
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if( rw->ltrw_r_active > 0 || rw->ltrw_w_active > 0) {
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ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
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return LDAP_PVT_THREAD_EBUSY;
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}
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/* waiting threads? */
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if( rw->ltrw_r_wait > 0 || rw->ltrw_w_wait > 0) {
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ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
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return LDAP_PVT_THREAD_EBUSY;
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}
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rw->ltrw_valid = 0;
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ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
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ldap_pvt_thread_mutex_destroy( &rw->ltrw_mutex );
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ldap_pvt_thread_cond_destroy( &rw->ltrw_read );
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ldap_pvt_thread_cond_destroy( &rw->ltrw_write );
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LDAP_FREE(rw);
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*rwlock = NULL;
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return 0;
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}
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int ldap_pvt_thread_rdwr_rlock( ldap_pvt_thread_rdwr_t *rwlock )
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{
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struct ldap_int_thread_rdwr_s *rw;
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assert( rwlock != NULL );
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rw = *rwlock;
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assert( rw != NULL );
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assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
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if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
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return LDAP_PVT_THREAD_EINVAL;
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ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
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assert( rw->ltrw_w_active >= 0 );
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assert( rw->ltrw_w_wait >= 0 );
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assert( rw->ltrw_r_active >= 0 );
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assert( rw->ltrw_r_wait >= 0 );
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if( rw->ltrw_w_active > 0 ) {
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/* writer is active */
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rw->ltrw_r_wait++;
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do {
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ldap_pvt_thread_cond_wait(
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&rw->ltrw_read, &rw->ltrw_mutex );
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} while( rw->ltrw_w_active > 0 );
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rw->ltrw_r_wait--;
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assert( rw->ltrw_r_wait >= 0 );
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}
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rw->ltrw_r_active++;
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ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
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return 0;
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}
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int ldap_pvt_thread_rdwr_rtrylock( ldap_pvt_thread_rdwr_t *rwlock )
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{
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struct ldap_int_thread_rdwr_s *rw;
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assert( rwlock != NULL );
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rw = *rwlock;
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assert( rw != NULL );
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assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
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if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
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return LDAP_PVT_THREAD_EINVAL;
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ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
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assert( rw->ltrw_w_active >= 0 );
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assert( rw->ltrw_w_wait >= 0 );
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assert( rw->ltrw_r_active >= 0 );
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assert( rw->ltrw_r_wait >= 0 );
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if( rw->ltrw_w_active > 0) {
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ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
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return LDAP_PVT_THREAD_EBUSY;
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}
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rw->ltrw_r_active++;
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ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
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return 0;
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}
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int ldap_pvt_thread_rdwr_runlock( ldap_pvt_thread_rdwr_t *rwlock )
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{
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struct ldap_int_thread_rdwr_s *rw;
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assert( rwlock != NULL );
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rw = *rwlock;
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assert( rw != NULL );
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assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
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if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
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return LDAP_PVT_THREAD_EINVAL;
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ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
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rw->ltrw_r_active--;
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assert( rw->ltrw_w_active >= 0 );
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assert( rw->ltrw_w_wait >= 0 );
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assert( rw->ltrw_r_active >= 0 );
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assert( rw->ltrw_r_wait >= 0 );
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if (rw->ltrw_r_active == 0 && rw->ltrw_w_wait > 0 ) {
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ldap_pvt_thread_cond_signal( &rw->ltrw_write );
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}
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ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
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return 0;
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}
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int ldap_pvt_thread_rdwr_wlock( ldap_pvt_thread_rdwr_t *rwlock )
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{
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struct ldap_int_thread_rdwr_s *rw;
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assert( rwlock != NULL );
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rw = *rwlock;
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assert( rw != NULL );
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assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
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if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
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return LDAP_PVT_THREAD_EINVAL;
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ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
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assert( rw->ltrw_w_active >= 0 );
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assert( rw->ltrw_w_wait >= 0 );
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assert( rw->ltrw_r_active >= 0 );
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assert( rw->ltrw_r_wait >= 0 );
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if ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 ) {
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rw->ltrw_w_wait++;
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do {
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ldap_pvt_thread_cond_wait(
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&rw->ltrw_write, &rw->ltrw_mutex );
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} while ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 );
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rw->ltrw_w_wait--;
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assert( rw->ltrw_w_wait >= 0 );
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}
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rw->ltrw_w_active++;
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ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
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return 0;
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}
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int ldap_pvt_thread_rdwr_wtrylock( ldap_pvt_thread_rdwr_t *rwlock )
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{
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struct ldap_int_thread_rdwr_s *rw;
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assert( rwlock != NULL );
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rw = *rwlock;
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assert( rw != NULL );
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assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
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if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
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return LDAP_PVT_THREAD_EINVAL;
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ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
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assert( rw->ltrw_w_active >= 0 );
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assert( rw->ltrw_w_wait >= 0 );
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assert( rw->ltrw_r_active >= 0 );
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assert( rw->ltrw_r_wait >= 0 );
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if ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 ) {
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ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
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return LDAP_PVT_THREAD_EBUSY;
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}
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rw->ltrw_w_active++;
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ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
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return 0;
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}
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int ldap_pvt_thread_rdwr_wunlock( ldap_pvt_thread_rdwr_t *rwlock )
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{
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struct ldap_int_thread_rdwr_s *rw;
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assert( rwlock != NULL );
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rw = *rwlock;
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assert( rw != NULL );
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assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
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if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
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return LDAP_PVT_THREAD_EINVAL;
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ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
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rw->ltrw_w_active--;
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assert( rw->ltrw_w_active >= 0 );
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assert( rw->ltrw_w_wait >= 0 );
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assert( rw->ltrw_r_active >= 0 );
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assert( rw->ltrw_r_wait >= 0 );
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if (rw->ltrw_r_wait > 0) {
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ldap_pvt_thread_cond_broadcast( &rw->ltrw_read );
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} else if (rw->ltrw_w_wait > 0) {
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ldap_pvt_thread_cond_signal( &rw->ltrw_write );
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}
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ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
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return 0;
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}
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#ifdef LDAP_RDWR_DEBUG
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/* just for testing,
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* return 0 if false, suitable for assert(ldap_pvt_thread_rdwr_Xchk(rdwr))
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*
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* Currently they don't check if the calling thread is the one
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* that has the lock, just that there is a reader or writer.
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*
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* Basically sufficent for testing that places that should have
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* a lock are caught.
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*/
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int ldap_pvt_thread_rdwr_readers(ldap_pvt_thread_rdwr_t *rwlock)
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{
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struct ldap_int_thread_rdwr_s *rw;
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assert( rwlock != NULL );
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rw = *rwlock;
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assert( rw != NULL );
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assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
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assert( rw->ltrw_w_active >= 0 );
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assert( rw->ltrw_w_wait >= 0 );
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assert( rw->ltrw_r_active >= 0 );
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assert( rw->ltrw_r_wait >= 0 );
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return( rw->ltrw_r_active );
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}
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int ldap_pvt_thread_rdwr_writers(ldap_pvt_thread_rdwr_t *rwlock)
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{
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struct ldap_int_thread_rdwr_s *rw;
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assert( rwlock != NULL );
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rw = *rwlock;
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assert( rw != NULL );
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assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
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assert( rw->ltrw_w_active >= 0 );
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assert( rw->ltrw_w_wait >= 0 );
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assert( rw->ltrw_r_active >= 0 );
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assert( rw->ltrw_r_wait >= 0 );
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return( rw->ltrw_w_active );
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}
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int ldap_pvt_thread_rdwr_active(ldap_pvt_thread_rdwr_t *rwlock)
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{
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struct ldap_int_thread_rdwr_s *rw;
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assert( rwlock != NULL );
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rw = *rwlock;
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assert( rw != NULL );
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assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
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assert( rw->ltrw_w_active >= 0 );
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assert( rw->ltrw_w_wait >= 0 );
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assert( rw->ltrw_r_active >= 0 );
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assert( rw->ltrw_r_wait >= 0 );
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return(ldap_pvt_thread_rdwr_readers(rw) +
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ldap_pvt_thread_rdwr_writers(rw));
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}
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#endif /* LDAP_DEBUG */
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#endif /* LDAP_THREAD_HAVE_RDWR */
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