LDAP_RDWR_DEBUG update:

- Avoid buffer overrun when too many readers.
- When remoinv reader ID, move one ID instead of all later IDs in array.
- assert(correct lock owner) before unlocking a write lock.

diff --git a/libraries/libldap_r/rdwr.c b/libraries/libldap_r/rdwr.c
index 45f642de4f46b0815959615c3803b0ffd7e76210..de6b23cb4a21cd810e7570dd26bad9faa81f7932 100644 (file)
--- a/libraries/libldap_r/rdwr.c
+++ b/libraries/libldap_r/rdwr.c
@@ -64,6 +64,7 @@ struct ldap_int_thread_rdwr_s {
 #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
@@ -173,7 +174,10 @@ int ldap_pvt_thread_rdwr_rlock( ldap_pvt_thread_rdwr_t *rwlock )
        }
 
 #ifdef LDAP_RDWR_DEBUG
-       rw->ltrw_readers[rw->ltrw_r_active] = ldap_pvt_thread_self();
+       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++;
 
@@ -209,7 +213,10 @@ int ldap_pvt_thread_rdwr_rtrylock( ldap_pvt_thread_rdwr_t *rwlock )
        }
 
 #ifdef LDAP_RDWR_DEBUG
-       rw->ltrw_readers[rw->ltrw_r_active] = ldap_pvt_thread_self();
+       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++;
 
@@ -233,23 +240,25 @@ 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 */
-       { int i, j;
-       ldap_pvt_thread_t self = ldap_pvt_thread_self();
-
-       for (i=0; i<rw->ltrw_r_active;i++)
        {
-               if (rw->ltrw_readers[i] == self) {
-                       for (j=i; j<rw->ltrw_r_active-1; j++)
-                               rw->ltrw_readers[j] = rw->ltrw_readers[j+1];
-                       rw->ltrw_readers[j] = 0;
-                       break;
+               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
-       rw->ltrw_r_active--;
 
        assert( rw->ltrw_w_active >= 0 ); 
        assert( rw->ltrw_w_wait >= 0 ); 
@@ -372,6 +381,7 @@ int ldap_pvt_thread_rdwr_wunlock( ldap_pvt_thread_rdwr_t *rwlock )
        }
 
 #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 );