Problems of partially freed waiting quque fixed (BUG#35040)

mysys/wqueue.c:
  Problems of partially freed waiting quque fixed.
storage/maria/unittest/ma_pagecache_rwconsist.c:
  Explicitly assigned initial value for increasing readability.
  Dbug file flush after each line for better debugging.
  Fixed code style.

mysys/wqueue.c

@@ -140,55 +140,58 @@ void wqueue_release_queue(WQUEUE *wqueue)
   @brief Removes all threads waiting for read or first one waiting for write.
 
   @param wqueue          pointer to the queue structure
-  @apram thread          pointer to the thread to be added to the queue
+  @param thread          pointer to the thread to be added to the queue
+
+  @note This function is applicable only to single linked lists.
 */
 
 void wqueue_release_one_locktype_from_queue(WQUEUE *wqueue)
 {
   struct st_my_thread_var *last= wqueue->last_thread;
   struct st_my_thread_var *next= last->next;
-  struct st_my_thread_var **prev= &last->next;
   struct st_my_thread_var *thread;
-  struct st_my_thread_var *new_last= NULL;
+  struct st_my_thread_var *new_list= NULL;
   uint first_type= next->lock_type;
   if (first_type == MY_PTHREAD_LOCK_WRITE)
   {
     /* release first waiting for write lock */
-    thread= next;
-    pthread_cond_signal(&thread->suspend);
-    if (thread == last)
+    pthread_cond_signal(&next->suspend);
+#ifndef DBUG_OFF
+    next->prev= NULL; /* force segfault if used */
+#endif
+    if (next == last)
       wqueue->last_thread= NULL;
-    *prev= thread->next;
-    thread->next= NULL;
+    else
+      last->next= next->next;
+    next->next= NULL;
     return;
   }
   do
   {
     thread= next;
     next= thread->next;
+#ifndef DBUG_OFF
+    thread->prev= NULL; /* force segfault if used */
+#endif
     if (thread->lock_type == MY_PTHREAD_LOCK_WRITE)
     {
       /* skip waiting for write lock */
-      *prev= thread;
-      prev= &thread->next;
-      new_last= NULL;
+      if (new_list)
+      {
+        thread->next= new_list->next;
+        new_list= new_list->next= thread;
+      }
+      else
+        new_list= thread->next= thread;
     }
     else
     {
       /* release waiting for read lock */
       pthread_cond_signal(&thread->suspend);
-      new_last= thread->next;
       thread->next= NULL;
     }
   } while (thread != last);
-  if (new_last)
-  {
-    /* last was deleted */
-    if (new_last == last)
-      wqueue->last_thread= NULL; /* empty list */
-    else
-      wqueue->last_thread= new_last;
-  }
+  wqueue->last_thread= new_list;
 }
 
 

storage/maria/unittest/ma_pagecache_rwconsist.c

@@ -37,7 +37,7 @@ static char *file1_name= (char*)"page_cache_test_file_1";
 static PAGECACHE_FILE file1;
 static pthread_cond_t COND_thread_count;
 static pthread_mutex_t LOCK_thread_count;
-static uint thread_count;
+static uint thread_count= 0;
 static PAGECACHE pagecache;
 
 static uint number_of_readers= 5;
@@ -214,7 +214,7 @@ int main(int argc __attribute__((unused)),
 #if defined(__WIN__)
   default_dbug_option= "d:t:i:O,\\test_pagecache_consist.trace";
 #else
-  default_dbug_option= "d:t:i:o,/tmp/test_pagecache_consist.trace";
+  default_dbug_option= "d:t:i:O,/tmp/test_pagecache_consist.trace";
 #endif
   if (argc > 1)
   {
@@ -335,8 +335,8 @@ int main(int argc __attribute__((unused)),
   pthread_mutex_lock(&LOCK_thread_count);
   while (thread_count)
   {
-    if ((error= pthread_cond_wait(&COND_thread_count,&LOCK_thread_count)))
-      diag("COND_thread_count: %d from pthread_cond_wait\n",error);
+    if ((error= pthread_cond_wait(&COND_thread_count, &LOCK_thread_count)))
+      diag("COND_thread_count: %d from pthread_cond_wait\n", error);
   }
   pthread_mutex_unlock(&LOCK_thread_count);
   DBUG_PRINT("info", ("thread ended"));