thread accounting in libpthread

[Daniel Eischen]

On Sun, 20 Feb 2005, Kazuaki Oda wrote:

> Daniel Eischen wrote:
>
> >If there was no running thread before kse_wait(), then after
> >kse_wait() returns and if there are completed threads, then
> >either one thread completed or N threads completed.  Either
> >way, they are all added to the end of the run queue.  But
> >the run queue must have been empty to begin with, otherwise
> >kse_wait() would not have been called.  So it doesn't matter
> >whether they are added to the head or the end of the queue.
> >If one thread completes, then it will be run right away
> >since it will be the only thread in the queue.  If N threads
> >complete (assuming they are all at the same priority) then
> >the first thread pulled from the completed list will be
> >run first since it will be the first thread added to the
> >run queue.
>
> Did you try to run the program attached to my past mail?  If you run it
> under X11 terminal on a UP machine, you probably get a unfair result.

I don't get much of a difference with and without patch at
end.  Depending on what your threads are blocking on, I
think it can be random.

  with patch
  ----------
  thread 00: 4716
  thread 01: 4307
  thread 02: 3631
  thread 03: 3698
  thread 04: 3455

  without patch
  -------------
  thread 00: 4289
  thread 01: 2903
  thread 02: 4352
  thread 03: 3444
  thread 04: 4405

-- 
DE

Index: thread/thr_kern.c
===================================================================
RCS file: /opt/FreeBSD/cvs/src/lib/libpthread/thread/thr_kern.c,v
retrieving revision 1.116
diff -u -r1.116 thr_kern.c
--- thread/thr_kern.c	18 Dec 2004 18:07:37 -0000	1.116
+++ thread/thr_kern.c	20 Feb 2005 15:36:33 -0000
@@ -1465,14 +1465,22 @@
 static void
 kse_check_completed(struct kse *kse)
 {
-	struct pthread *thread;
+	TAILQ_HEAD(, pthread) completeq;
+	struct pthread *thread, *next;
 	struct kse_thr_mailbox *completed;
 	int sig;

 	if ((completed = kse->k_kcb->kcb_kmbx.km_completed) != NULL) {
+		TAILQ_INIT(&completeq);
 		kse->k_kcb->kcb_kmbx.km_completed = NULL;
 		while (completed != NULL) {
 			thread = completed->tm_udata;
+			TAILQ_INSERT_HEAD(&completeq, thread, pqe);
+			completed = completed->tm_next;
+		}
+		for (thread = TAILQ_FIRST(&completeq); thread != NULL;
+		    thread = next) {
+			next = TAILQ_NEXT(thread, pqe);
 			DBG_MSG("Found completed thread %p, name %s\n",
 			    thread,
 			    (thread->name == NULL) ? "none" : thread->name);
@@ -1505,7 +1513,6 @@
 					    &thread->tcb->tcb_tmbx.tm_syncsig);
 				thread->tcb->tcb_tmbx.tm_syncsig.si_signo = 0;
 			}
-			completed = completed->tm_next;
 		}
 	}
 }