From e3a513aa0d9f133917ec7e914452a40eeee1b05a Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Mon, 5 Feb 2007 14:26:41 +0000
Subject: [PATCH] fix scheduler bug; see plt-scheme 2007-Feb-5 post and reply

svn: r5552
---
 src/mzscheme/src/schpriv.h | 2 +-
 src/mzscheme/src/sema.c    | 9 ++++++---
 src/mzscheme/src/thread.c  | 8 +++-----
 3 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/src/mzscheme/src/schpriv.h b/src/mzscheme/src/schpriv.h
index 66e226ce99..d35ca785b7 100644
--- a/src/mzscheme/src/schpriv.h
+++ b/src/mzscheme/src/schpriv.h
@@ -385,7 +385,7 @@ typedef struct Scheme_Security_Guard {
 
 /* Always allocated on the stack: */
 typedef struct {
-  int false_positive_ok;  /* non-zero => return 1 to swap in thread rather than running Scheme code */
+  Scheme_Thread *false_positive_ok;  /* non-zero => return 1 to swap in thread rather than running Scheme code */
   int potentially_false_positive; /* => returning 1 to swap thread in, but truth may be 0 */
   Scheme_Object *current_syncing;
   double sleep_end;
diff --git a/src/mzscheme/src/sema.c b/src/mzscheme/src/sema.c
index 33515586cb..ea698bf82b 100644
--- a/src/mzscheme/src/sema.c
+++ b/src/mzscheme/src/sema.c
@@ -430,7 +430,10 @@ static void ext_get_into_line(Scheme_Object *ch, Scheme_Schedule_Info *sinfo)
   /* Get into line */
   w = MALLOC_ONE_RT(Scheme_Channel_Syncer);
   w->so.type = scheme_channel_syncer_type;
-  w->p = scheme_current_thread;
+  if (sinfo->false_positive_ok)
+    w->p = sinfo->false_positive_ok;
+  else
+    w->p = scheme_current_thread;
   w->syncing = (Syncing *)sinfo->current_syncing;
   w->obj = ch;
   w->syncing_i = sinfo->w_i;
@@ -459,8 +462,8 @@ static int try_channel(Scheme_Sema *sema, Syncing *syncing, int pos, Scheme_Obje
 	w = w->next;
       } else {
 	Scheme_Channel_Put *chp = (Scheme_Channel_Put *)w->obj;
-	
-	if (!w->syncing->result && !pending_break(w->p)) {
+
+        if (!w->syncing->result && !pending_break(w->p)) {
 	  w->picked = 1;
 	  w->syncing->result = w->syncing_i + 1;
 	  if (w->syncing->disable_break)
diff --git a/src/mzscheme/src/thread.c b/src/mzscheme/src/thread.c
index 70cd9c40cd..83c35d062a 100644
--- a/src/mzscheme/src/thread.c
+++ b/src/mzscheme/src/thread.c
@@ -3288,9 +3288,7 @@ END_XFORM_SKIP;
 
 #endif
 
-#define FALSE_POS_OK_INIT 1
-
-static void init_schedule_info(Scheme_Schedule_Info *sinfo, int false_pos_ok, 
+static void init_schedule_info(Scheme_Schedule_Info *sinfo, Scheme_Thread *false_pos_ok, 
 			       double sleep_end)
 {
   sinfo->false_positive_ok = false_pos_ok;
@@ -3647,7 +3645,7 @@ void scheme_thread_block(float sleep_time)
 	  if (next->block_check) {
 	    Scheme_Ready_Fun_FPC f = (Scheme_Ready_Fun_FPC)next->block_check;
 	    Scheme_Schedule_Info sinfo;
-	    init_schedule_info(&sinfo, FALSE_POS_OK_INIT, next->sleep_end);
+	    init_schedule_info(&sinfo, next, next->sleep_end);
 	    if (f(next->blocker, &sinfo))
 	      break;
 	    next->sleep_end = sinfo.sleep_end;
@@ -3795,7 +3793,7 @@ void scheme_thread_block(float sleep_time)
 	if (p->block_check) {
 	  Scheme_Ready_Fun_FPC f = (Scheme_Ready_Fun_FPC)p->block_check;
 	  Scheme_Schedule_Info sinfo;
-	  init_schedule_info(&sinfo, FALSE_POS_OK_INIT, sleep_end);
+	  init_schedule_info(&sinfo, p, sleep_end);
 	  if (f(p->blocker, &sinfo)) {
 	    sleep_end = 0;
 	  } else {