Re: [AD] Potential uthreads hang on cleanup?

[Peter Wang <tjaden@xxxxxxxxxx>]

Chris wrote:

> As detailed here:
> http://www.allegro.cc/forums/view_thread.php?_id=438553#target
>
> it seems pthread_cancel has some problems shutting down on some 
> systems. The poster says it returns what resolves to "Resource 
> temporarily unavailable", although my man pages say pthread_cancel can 
> only fail if the requested thread doesn't exist, so I'm not really 
> sure what's going on or what the right way to deal with it is. In 
> either case, I attached a simple patch that fixes his issue.


The right way to do things is not to use pthread_cancel at all.  Sorry, 
I was still new to threads when I wrote that code.  Patch attached, but 
I didn't test it with Kdevelop or whatever.

Peter

Index: uthreads.c
===================================================================
RCS file: /cvsroot/alleg/allegro/src/unix/uthreads.c,v
retrieving revision 1.19
diff -u -r1.19 uthreads.c
--- uthreads.c	29 Nov 2004 07:58:34 -0000	1.19
+++ uthreads.c	10 Dec 2004 08:08:03 -0000
@@ -38,6 +38,7 @@
 static int max_func; /* highest+1 used entry */
 
 static pthread_t thread = 0;
+static int thread_alive = FALSE;
 static pthread_mutex_t cli_mutex;
 static pthread_cond_t cli_cond;
 static int cli_count;
@@ -70,12 +71,14 @@
    unsigned long interval;
    int n;
 
+   ASSERT(thread_alive);
+
    block_all_signals();
 
    interval = 0;
    gettimeofday(&old_time, 0);
 
-   while (1) {
+   while (thread_alive) {
       gettimeofday(&new_time, 0);
       /* add the new time difference to the remainder of the old difference */
       interval += ((new_time.tv_sec - old_time.tv_sec) * 1000000L +
@@ -107,7 +110,6 @@
       delay.tv_sec = 0;
       delay.tv_usec = 1000;
       select(0, NULL, NULL, NULL, &delay);
-      pthread_testcancel();
    }
 
    return NULL;
@@ -123,6 +125,7 @@
    int i;
 
    ASSERT(thread == 0);
+   ASSERT(!thread_alive);
 
    for (i = 0; i < MAX_FUNCS; i++)
       funcs[i] = NULL;
@@ -133,7 +136,9 @@
    pthread_mutex_init(&cli_mutex, NULL);
    pthread_cond_init(&cli_cond, NULL);
 
+   thread_alive = TRUE;
    if (pthread_create(&thread, NULL, bg_man_pthreads_threadfunc, NULL)) {
+      thread_alive = FALSE;
       pthread_mutex_destroy(&cli_mutex);
       pthread_cond_destroy(&cli_cond);
       thread = 0;
@@ -150,8 +155,10 @@
  */
 static void bg_man_pthreads_exit(void)
 {
+   ASSERT(!!thread == !!thread_alive);
+
    if (thread) {
-      pthread_cancel(thread);
+      thread_alive = FALSE;
       pthread_join(thread, NULL);
       pthread_mutex_destroy(&cli_mutex);
       pthread_cond_destroy(&cli_cond);