--- src/include/cpu.h	Mon Mar 11 03:37:34 2002
+++ src/include/cpu.h	Mon Mar 18 17:01:32 2002
@@ -179,7 +179,7 @@
 
   /* Flag setting and clearing, and testing */
         /* interrupt flag */
-#define set_IF() ((_EFLAGS |= (VIF | IF)), (dpmi_eflags |= IF), pic_sti())
+#define set_IF() ((_EFLAGS |= (VIF | IF)), (dpmi_eflags |= IF), is_cli = 0, pic_sti())
 #define clear_IF() ((_EFLAGS &= ~(VIF | IF)), (dpmi_eflags &= ~IF), pic_cli())
 #define isset_IF() ((_EFLAGS & VIF) != 0)
        /* carry flag */
--- src/dosext/dpmi/dpmi.h	Sat Nov 17 05:40:34 2001
+++ src/dosext/dpmi/dpmi.h	Sun Nov 25 22:04:18 2001
@@ -40,6 +40,7 @@
 EXTERN int in_dpmi_timer_int INIT(0);
 EXTERN int dpmi_mhp_TF INIT(0);
 EXTERN unsigned char dpmi_mhp_intxxtab[256] INIT({0});
+EXTERN int is_cli INIT(0);
 
 void dpmi_get_entry_point();
 
@@ -64,6 +65,8 @@
 void dpmi_mhp_setreg(int regnum, unsigned long val);
 #endif
 
+void add_cli_to_blacklist(void);
+
 /* DANG_BEGIN_REMARK
  * Handling of the virtual interrupt flag is still not correct and there
  * are many open questions since DPMI specifications are unclear in this
@@ -78,7 +81,7 @@
 
 #define dpmi_cli() 	({ dpmi_eflags &= ~IF; pic_cli(); })
 
-#define dpmi_sti() 	({ dpmi_eflags |= IF; pic_sti(); })
+#define dpmi_sti() 	({ dpmi_eflags |= IF; is_cli = 0; pic_sti(); })
 
 #define CHECK_SELECTOR(x) \
 { if ( (((x) >> 3) >= MAX_SELECTORS) || (!Segments[((x) >> 3)].used) \
--- src/dosext/dpmi/dpmi.c	Sat Nov 24 02:48:43 2001
+++ src/dosext/dpmi/dpmi.c	Sun Nov 25 22:04:32 2001
@@ -118,6 +118,12 @@
 /* for real mode call back, DPMI function 0x303 0x304 */
 static RealModeCallBack realModeCallBack[DPMI_MAX_CLIENTS][0x10];
 
+#define CLI_BLACKLIST_LEN 128
+static unsigned char * cli_blacklist[CLI_BLACKLIST_LEN];
+static unsigned char * current_cli;
+static int cli_blacklisted = 0;
+static int find_cli_in_blacklist(unsigned char *);
+
 static RealModeCallBack mouseCallBack; /* user\'s mouse routine */
 
 struct vm86_regs DPMI_rm_stack[DPMI_max_rec_rm_func];
@@ -1917,6 +1923,7 @@
     if (ldt_buffer) free(ldt_buffer);
     if (pm_stack) free(pm_stack);
   }
+  cli_blacklisted = 0;
   in_dpmi_dos_int = 1;
   in_dpmi--;
   in_win31 = 0;
@@ -3157,7 +3164,14 @@
 	dbug_printf("OUCH! deadly loop, cannot continue");
 	leavedos(97);
       }
+      if (find_cli_in_blacklist(lina)) {
+        D_printf("DPMI: Ignoring blacklisted cli\n");
+	break;
+      }
+      current_cli = lina;
       dpmi_cli();
+      if (!is_cli)
+	is_cli = 1;
       break;
     case 0xfb:			/* sti */
       _eip += 1;
@@ -3884,4 +3898,33 @@
 
 #endif /* dosdebug support */
 
+void add_cli_to_blacklist(void)
+{
+  if (*current_cli != 0xfa) {
+    error("DPMI: add_cli_to_blacklist() called with no cli at %p (0x%x)!\n",
+      current_cli, *current_cli);
+    return;
+  }
+  if (cli_blacklisted < CLI_BLACKLIST_LEN) {
+    if (debug_level('M') > 5)
+      D_printf("DPMI: adding cli to blacklist: lina=%p\n", current_cli);
+    cli_blacklist[cli_blacklisted++] = current_cli;
+  }
+  else
+    D_printf("DPMI: Warning: cli blacklist is full!\n");
+}
+
+static int find_cli_in_blacklist(unsigned char * cur_cli)
+{
+int i;
+  if (debug_level('M') > 8)
+    D_printf("DPMI: searching blacklist (%d elements) for cli (lina=%p)\n",
+      cli_blacklisted, cur_cli);
+  for (i=0; i<cli_blacklisted; i++) {
+    if (cli_blacklist[i] == cur_cli)
+      return 1;
+  }
+  return 0;
+}
+
 #undef DPMI_C
--- src/base/dev/misc/timers.c	Sat Nov 24 05:02:59 2001
+++ src/base/dev/misc/timers.c	Sat Nov 24 05:04:20 2001
@@ -154,6 +154,20 @@
   /* Save old value of the timer */
   time_old = time_curr;
   
+  if (config.features[0] && in_dpmi && !in_dpmi_dos_int && is_cli) {
+/*
+   XXX as IF is not set by popf, we have to set it explicitly after a
+   reasonable delay. This will allow Doom to work with sound one day.
+   $_features="0:10" is recommended.
+*/
+    if (is_cli++ >= config.features[0]) {
+      D_printf("DPMI: Warning: Interrupts were disabled for too long, "
+      "re-enabling.\n");
+      add_cli_to_blacklist();
+      dpmi_sti();
+    }
+  }
+  
   /* test for stuck interrupts, trigger any scheduled interrupts */
   pic_watch(&tp);
 }