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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 16:35:32 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 16:35:32 +0000 |
commit | 5ea77a75dd2d2158401331879f3c8f47940a732c (patch) | |
tree | d89dc06e9f4850a900f161e25f84e922c4f86cc8 /libraries/libldap/rdwr.c | |
parent | Initial commit. (diff) | |
download | openldap-5ea77a75dd2d2158401331879f3c8f47940a732c.tar.xz openldap-5ea77a75dd2d2158401331879f3c8f47940a732c.zip |
Adding upstream version 2.5.13+dfsg.upstream/2.5.13+dfsgupstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | libraries/libldap/rdwr.c | 463 |
1 files changed, 463 insertions, 0 deletions
diff --git a/libraries/libldap/rdwr.c b/libraries/libldap/rdwr.c new file mode 100644 index 0000000..dde9403 --- /dev/null +++ b/libraries/libldap/rdwr.c @@ -0,0 +1,463 @@ +/* $OpenLDAP$ */ +/* This work is part of OpenLDAP Software <http://www.openldap.org/>. + * + * Copyright 1998-2022 The OpenLDAP Foundation. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted only as authorized by the OpenLDAP + * Public License. + * + * A copy of this license is available in file LICENSE in the + * top-level directory of the distribution or, alternatively, at + * <http://www.OpenLDAP.org/license.html>. + */ +/* This work was initially developed by Kurt D. Zeilenga for inclusion + * in OpenLDAP Software. Additional significant contributors include: + * Stuart Lynne + */ + +/* + * This is an improved implementation of Reader/Writer locks does + * not protect writers from starvation. That is, if a writer is + * currently waiting on a reader, any new reader will get + * the lock before the writer. + * + * Does not support cancellation nor does any status checking. + */ +/* Adapted from publicly available examples for: + * "Programming with Posix Threads" + * by David R Butenhof, Addison-Wesley + * http://cseng.aw.com/bookpage.taf?ISBN=0-201-63392-2 + */ + +#include "portable.h" + +#include <ac/stdlib.h> + +#include <ac/errno.h> +#include <ac/string.h> +#include <ac/time.h> + +#include "ldap-int.h" + +#ifdef LDAP_R_COMPILE + +#include "ldap_pvt_thread.h" /* Get the thread interface */ +#define LDAP_THREAD_RDWR_IMPLEMENTATION +#include "ldap_thr_debug.h" /* May rename the symbols defined below */ + +/* + * implementations that provide their own compatible + * reader/writer locks define LDAP_THREAD_HAVE_RDWR + * in ldap_pvt_thread.h + */ +#ifndef LDAP_THREAD_HAVE_RDWR + +struct ldap_int_thread_rdwr_s { + ldap_pvt_thread_mutex_t ltrw_mutex; + ldap_pvt_thread_cond_t ltrw_read; /* wait for read */ + ldap_pvt_thread_cond_t ltrw_write; /* wait for write */ + int ltrw_valid; +#define LDAP_PVT_THREAD_RDWR_VALID 0x0bad + int ltrw_r_active; + int ltrw_w_active; + int ltrw_r_wait; + int ltrw_w_wait; +#ifdef LDAP_RDWR_DEBUG + /* keep track of who has these locks */ +#define MAX_READERS 32 + int ltrw_more_readers; /* Set if ltrw_readers[] is incomplete */ + ldap_pvt_thread_t ltrw_readers[MAX_READERS]; + ldap_pvt_thread_t ltrw_writer; +#endif +}; + +int +ldap_pvt_thread_rdwr_init( ldap_pvt_thread_rdwr_t *rwlock ) +{ + struct ldap_int_thread_rdwr_s *rw; + + assert( rwlock != NULL ); + + rw = (struct ldap_int_thread_rdwr_s *) LDAP_CALLOC( 1, + sizeof( struct ldap_int_thread_rdwr_s ) ); + if ( !rw ) + return LDAP_NO_MEMORY; + + /* we should check return results */ + ldap_pvt_thread_mutex_init( &rw->ltrw_mutex ); + ldap_pvt_thread_cond_init( &rw->ltrw_read ); + ldap_pvt_thread_cond_init( &rw->ltrw_write ); + + rw->ltrw_valid = LDAP_PVT_THREAD_RDWR_VALID; + + *rwlock = rw; + return 0; +} + +int +ldap_pvt_thread_rdwr_destroy( ldap_pvt_thread_rdwr_t *rwlock ) +{ + struct ldap_int_thread_rdwr_s *rw; + + assert( rwlock != NULL ); + rw = *rwlock; + + assert( rw != NULL ); + assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID ); + + if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID ) + return LDAP_PVT_THREAD_EINVAL; + + ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex ); + + assert( rw->ltrw_w_active >= 0 ); + assert( rw->ltrw_w_wait >= 0 ); + assert( rw->ltrw_r_active >= 0 ); + assert( rw->ltrw_r_wait >= 0 ); + + /* active threads? */ + if( rw->ltrw_r_active > 0 || rw->ltrw_w_active > 0) { + ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex ); + return LDAP_PVT_THREAD_EBUSY; + } + + /* waiting threads? */ + if( rw->ltrw_r_wait > 0 || rw->ltrw_w_wait > 0) { + ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex ); + return LDAP_PVT_THREAD_EBUSY; + } + + rw->ltrw_valid = 0; + + ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex ); + + ldap_pvt_thread_mutex_destroy( &rw->ltrw_mutex ); + ldap_pvt_thread_cond_destroy( &rw->ltrw_read ); + ldap_pvt_thread_cond_destroy( &rw->ltrw_write ); + + LDAP_FREE(rw); + *rwlock = NULL; + return 0; +} + +int ldap_pvt_thread_rdwr_rlock( ldap_pvt_thread_rdwr_t *rwlock ) +{ + struct ldap_int_thread_rdwr_s *rw; + + assert( rwlock != NULL ); + rw = *rwlock; + + assert( rw != NULL ); + assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID ); + + if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID ) + return LDAP_PVT_THREAD_EINVAL; + + ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex ); + + assert( rw->ltrw_w_active >= 0 ); + assert( rw->ltrw_w_wait >= 0 ); + assert( rw->ltrw_r_active >= 0 ); + assert( rw->ltrw_r_wait >= 0 ); + + if( rw->ltrw_w_active > 0 ) { + /* writer is active */ + + rw->ltrw_r_wait++; + + do { + ldap_pvt_thread_cond_wait( + &rw->ltrw_read, &rw->ltrw_mutex ); + } while( rw->ltrw_w_active > 0 ); + + rw->ltrw_r_wait--; + assert( rw->ltrw_r_wait >= 0 ); + } + +#ifdef LDAP_RDWR_DEBUG + if( rw->ltrw_r_active < MAX_READERS ) + rw->ltrw_readers[rw->ltrw_r_active] = ldap_pvt_thread_self(); + else + rw->ltrw_more_readers = 1; +#endif + rw->ltrw_r_active++; + + + ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex ); + + return 0; +} + +int ldap_pvt_thread_rdwr_rtrylock( ldap_pvt_thread_rdwr_t *rwlock ) +{ + struct ldap_int_thread_rdwr_s *rw; + + assert( rwlock != NULL ); + rw = *rwlock; + + assert( rw != NULL ); + assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID ); + + if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID ) + return LDAP_PVT_THREAD_EINVAL; + + ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex ); + + assert( rw->ltrw_w_active >= 0 ); + assert( rw->ltrw_w_wait >= 0 ); + assert( rw->ltrw_r_active >= 0 ); + assert( rw->ltrw_r_wait >= 0 ); + + if( rw->ltrw_w_active > 0) { + ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex ); + return LDAP_PVT_THREAD_EBUSY; + } + +#ifdef LDAP_RDWR_DEBUG + if( rw->ltrw_r_active < MAX_READERS ) + rw->ltrw_readers[rw->ltrw_r_active] = ldap_pvt_thread_self(); + else + rw->ltrw_more_readers = 1; +#endif + rw->ltrw_r_active++; + + ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex ); + + return 0; +} + +int ldap_pvt_thread_rdwr_runlock( ldap_pvt_thread_rdwr_t *rwlock ) +{ + struct ldap_int_thread_rdwr_s *rw; + + assert( rwlock != NULL ); + rw = *rwlock; + + assert( rw != NULL ); + assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID ); + + if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID ) + return LDAP_PVT_THREAD_EINVAL; + + ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex ); + + rw->ltrw_r_active--; +#ifdef LDAP_RDWR_DEBUG + /* Remove us from the list of readers */ + { + ldap_pvt_thread_t self = ldap_pvt_thread_self(); + int i, j; + for( i = j = rw->ltrw_r_active; i >= 0; i--) { + if (rw->ltrw_readers[i] == self) { + rw->ltrw_readers[i] = rw->ltrw_readers[j]; + rw->ltrw_readers[j] = 0; + break; + } + } + if( !rw->ltrw_more_readers ) + assert( i >= 0 ); + else if( j == 0 ) + rw->ltrw_more_readers = 0; + } +#endif + + assert( rw->ltrw_w_active >= 0 ); + assert( rw->ltrw_w_wait >= 0 ); + assert( rw->ltrw_r_active >= 0 ); + assert( rw->ltrw_r_wait >= 0 ); + + if (rw->ltrw_r_active == 0 && rw->ltrw_w_wait > 0 ) { + ldap_pvt_thread_cond_signal( &rw->ltrw_write ); + } + + ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex ); + + return 0; +} + +int ldap_pvt_thread_rdwr_wlock( ldap_pvt_thread_rdwr_t *rwlock ) +{ + struct ldap_int_thread_rdwr_s *rw; + + assert( rwlock != NULL ); + rw = *rwlock; + + assert( rw != NULL ); + assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID ); + + if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID ) + return LDAP_PVT_THREAD_EINVAL; + + ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex ); + + assert( rw->ltrw_w_active >= 0 ); + assert( rw->ltrw_w_wait >= 0 ); + assert( rw->ltrw_r_active >= 0 ); + assert( rw->ltrw_r_wait >= 0 ); + + if ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 ) { + rw->ltrw_w_wait++; + + do { + ldap_pvt_thread_cond_wait( + &rw->ltrw_write, &rw->ltrw_mutex ); + } while ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 ); + + rw->ltrw_w_wait--; + assert( rw->ltrw_w_wait >= 0 ); + } + +#ifdef LDAP_RDWR_DEBUG + rw->ltrw_writer = ldap_pvt_thread_self(); +#endif + rw->ltrw_w_active++; + + ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex ); + + return 0; +} + +int ldap_pvt_thread_rdwr_wtrylock( ldap_pvt_thread_rdwr_t *rwlock ) +{ + struct ldap_int_thread_rdwr_s *rw; + + assert( rwlock != NULL ); + rw = *rwlock; + + assert( rw != NULL ); + assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID ); + + if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID ) + return LDAP_PVT_THREAD_EINVAL; + + ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex ); + + assert( rw->ltrw_w_active >= 0 ); + assert( rw->ltrw_w_wait >= 0 ); + assert( rw->ltrw_r_active >= 0 ); + assert( rw->ltrw_r_wait >= 0 ); + + if ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 ) { + ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex ); + return LDAP_PVT_THREAD_EBUSY; + } + +#ifdef LDAP_RDWR_DEBUG + rw->ltrw_writer = ldap_pvt_thread_self(); +#endif + rw->ltrw_w_active++; + + ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex ); + + return 0; +} + +int ldap_pvt_thread_rdwr_wunlock( ldap_pvt_thread_rdwr_t *rwlock ) +{ + struct ldap_int_thread_rdwr_s *rw; + + assert( rwlock != NULL ); + rw = *rwlock; + + assert( rw != NULL ); + assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID ); + + if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID ) + return LDAP_PVT_THREAD_EINVAL; + + ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex ); + + rw->ltrw_w_active--; + + assert( rw->ltrw_w_active >= 0 ); + assert( rw->ltrw_w_wait >= 0 ); + assert( rw->ltrw_r_active >= 0 ); + assert( rw->ltrw_r_wait >= 0 ); + + if (rw->ltrw_r_wait > 0) { + ldap_pvt_thread_cond_broadcast( &rw->ltrw_read ); + + } else if (rw->ltrw_w_wait > 0) { + ldap_pvt_thread_cond_signal( &rw->ltrw_write ); + } + +#ifdef LDAP_RDWR_DEBUG + assert( rw->ltrw_writer == ldap_pvt_thread_self() ); + rw->ltrw_writer = 0; +#endif + ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex ); + + return 0; +} + +#ifdef LDAP_RDWR_DEBUG + +/* just for testing, + * return 0 if false, suitable for assert(ldap_pvt_thread_rdwr_Xchk(rdwr)) + * + * Currently they don't check if the calling thread is the one + * that has the lock, just that there is a reader or writer. + * + * Basically sufficient for testing that places that should have + * a lock are caught. + */ + +int ldap_pvt_thread_rdwr_readers(ldap_pvt_thread_rdwr_t *rwlock) +{ + struct ldap_int_thread_rdwr_s *rw; + + assert( rwlock != NULL ); + rw = *rwlock; + + assert( rw != NULL ); + assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID ); + assert( rw->ltrw_w_active >= 0 ); + assert( rw->ltrw_w_wait >= 0 ); + assert( rw->ltrw_r_active >= 0 ); + assert( rw->ltrw_r_wait >= 0 ); + + return( rw->ltrw_r_active ); +} + +int ldap_pvt_thread_rdwr_writers(ldap_pvt_thread_rdwr_t *rwlock) +{ + struct ldap_int_thread_rdwr_s *rw; + + assert( rwlock != NULL ); + rw = *rwlock; + + assert( rw != NULL ); + assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID ); + assert( rw->ltrw_w_active >= 0 ); + assert( rw->ltrw_w_wait >= 0 ); + assert( rw->ltrw_r_active >= 0 ); + assert( rw->ltrw_r_wait >= 0 ); + + return( rw->ltrw_w_active ); +} + +int ldap_pvt_thread_rdwr_active(ldap_pvt_thread_rdwr_t *rwlock) +{ + struct ldap_int_thread_rdwr_s *rw; + + assert( rwlock != NULL ); + rw = *rwlock; + + assert( rw != NULL ); + assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID ); + assert( rw->ltrw_w_active >= 0 ); + assert( rw->ltrw_w_wait >= 0 ); + assert( rw->ltrw_r_active >= 0 ); + assert( rw->ltrw_r_wait >= 0 ); + + return(ldap_pvt_thread_rdwr_readers(rwlock) + + ldap_pvt_thread_rdwr_writers(rwlock)); +} + +#endif /* LDAP_RDWR_DEBUG */ + +#endif /* LDAP_THREAD_HAVE_RDWR */ + +#endif /* LDAP_R_COMPILE */ |