Comment fixes.

[openldap] / libraries / libldap_r / rdwr.c

diff --git a/libraries/libldap_r/rdwr.c b/libraries/libldap_r/rdwr.c
index 1be3f96211be8360e9e3548822b24faf7a9e2fed..47ed08f8242276e45144269d857ca839ff9a15b0 100644 (file)
--- a/libraries/libldap_r/rdwr.c
+++ b/libraries/libldap_r/rdwr.c
@@ -1,7 +1,7 @@
 /* $OpenLDAP$ */
 /* This work is part of OpenLDAP Software <http://www.openldap.org/>.
  *
- * Copyright 1998-2003 The OpenLDAP Foundation.
+ * Copyright 1998-2007 The OpenLDAP Foundation.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -12,15 +12,19 @@
  * 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.
-*/
+ * 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 publically available examples for:
  *     "Programming with Posix Threads"
  *             by David R Butenhof, Addison-Wesley 
@@ -36,7 +40,9 @@
 #include <ac/time.h>
 
 #include "ldap-int.h"
-#include "ldap_pvt_thread.h"
+#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 
@@ -55,6 +61,13 @@ struct ldap_int_thread_rdwr_s {
        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 
@@ -66,6 +79,8 @@ ldap_pvt_thread_rdwr_init( ldap_pvt_thread_rdwr_t *rwlock )
 
        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 );
@@ -158,8 +173,15 @@ int ldap_pvt_thread_rdwr_rlock( ldap_pvt_thread_rdwr_t *rwlock )
                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;
@@ -190,6 +212,12 @@ int ldap_pvt_thread_rdwr_rtrylock( ldap_pvt_thread_rdwr_t *rwlock )
                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 );
@@ -213,6 +241,24 @@ int ldap_pvt_thread_rdwr_runlock( ldap_pvt_thread_rdwr_t *rwlock )
        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 ); 
@@ -260,6 +306,9 @@ int ldap_pvt_thread_rdwr_wlock( ldap_pvt_thread_rdwr_t *rwlock )
                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 );
@@ -292,6 +341,9 @@ int ldap_pvt_thread_rdwr_wtrylock( ldap_pvt_thread_rdwr_t *rwlock )
                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 );
@@ -328,6 +380,10 @@ int ldap_pvt_thread_rdwr_wunlock( ldap_pvt_thread_rdwr_t *rwlock )
                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;
@@ -393,10 +449,10 @@ int ldap_pvt_thread_rdwr_active(ldap_pvt_thread_rdwr_t *rwlock)
        assert( rw->ltrw_r_active >= 0 ); 
        assert( rw->ltrw_r_wait >= 0 ); 
 
-       return(ldap_pvt_thread_rdwr_readers(rw) +
-              ldap_pvt_thread_rdwr_writers(rw));
+       return(ldap_pvt_thread_rdwr_readers(rwlock) +
+              ldap_pvt_thread_rdwr_writers(rwlock));
 }
 
-#endif /* LDAP_DEBUG */
+#endif /* LDAP_RDWR_DEBUG */
 
 #endif /* LDAP_THREAD_HAVE_RDWR */