1 files changed, 463 insertions, 0 deletions
diff --git a/libraries/libldap/rdwr.c b/libraries/libldap/rdwr.c
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+/* $OpenLDAP$ */
+/* 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 */