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459 lines
11 KiB
C
459 lines
11 KiB
C
/* $OpenLDAP$ */
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/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
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*
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* Copyright 1998-2017 The OpenLDAP Foundation.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted only as authorized by the OpenLDAP
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* Public License.
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*
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* A copy of this license is available in file LICENSE in the
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* top-level directory of the distribution or, alternatively, at
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* <http://www.OpenLDAP.org/license.html>.
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*/
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/* This work was initially developed by Kurt D. Zeilenga for inclusion
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* in OpenLDAP Software. Additional significant contributors include:
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* Stuart Lynne
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*/
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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" /* Get the thread interface */
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#define LDAP_THREAD_RDWR_IMPLEMENTATION
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#include "ldap_thr_debug.h" /* May rename the symbols defined below */
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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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#ifdef LDAP_RDWR_DEBUG
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/* keep track of who has these locks */
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#define MAX_READERS 32
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int ltrw_more_readers; /* Set if ltrw_readers[] is incomplete */
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ldap_pvt_thread_t ltrw_readers[MAX_READERS];
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ldap_pvt_thread_t ltrw_writer;
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#endif
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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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if ( !rw )
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return LDAP_NO_MEMORY;
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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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#ifdef LDAP_RDWR_DEBUG
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if( rw->ltrw_r_active < MAX_READERS )
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rw->ltrw_readers[rw->ltrw_r_active] = ldap_pvt_thread_self();
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else
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rw->ltrw_more_readers = 1;
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#endif
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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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#ifdef LDAP_RDWR_DEBUG
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if( rw->ltrw_r_active < MAX_READERS )
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rw->ltrw_readers[rw->ltrw_r_active] = ldap_pvt_thread_self();
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else
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rw->ltrw_more_readers = 1;
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#endif
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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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#ifdef LDAP_RDWR_DEBUG
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/* Remove us from the list of readers */
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{
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ldap_pvt_thread_t self = ldap_pvt_thread_self();
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int i, j;
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for( i = j = rw->ltrw_r_active; i >= 0; i--) {
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if (rw->ltrw_readers[i] == self) {
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rw->ltrw_readers[i] = rw->ltrw_readers[j];
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rw->ltrw_readers[j] = 0;
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break;
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}
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}
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if( !rw->ltrw_more_readers )
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assert( i >= 0 );
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else if( j == 0 )
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rw->ltrw_more_readers = 0;
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}
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#endif
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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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#ifdef LDAP_RDWR_DEBUG
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rw->ltrw_writer = ldap_pvt_thread_self();
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#endif
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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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#ifdef LDAP_RDWR_DEBUG
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rw->ltrw_writer = ldap_pvt_thread_self();
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#endif
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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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#ifdef LDAP_RDWR_DEBUG
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assert( rw->ltrw_writer == ldap_pvt_thread_self() );
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rw->ltrw_writer = 0;
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#endif
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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(rwlock) +
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ldap_pvt_thread_rdwr_writers(rwlock));
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}
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#endif /* LDAP_RDWR_DEBUG */
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#endif /* LDAP_THREAD_HAVE_RDWR */
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