diff --git a/C/absmi.c b/C/absmi.c
index 2ca523e77..53c5eb6e8 100755
--- a/C/absmi.c
+++ b/C/absmi.c
@@ -793,9 +793,16 @@ interrupt_handler_either( USES_REGS1 )
   return interrupt_handler( PASS_REGS1 );
 }
 
+/* trave interrupt calls */
+//#define DEBUG_INTERRUPTS 1
+
 static int
 interrupt_fail( USES_REGS1 )
 {
+#ifdef DEBUG_INTERRUPTS
+  fprintf(stderr,"[%d] %s:%d: INTERRUPT %lx (YENV=%p ENV=%p ASP=%p)\n",  (int)pthread_self(), \
+	  __FUNCTION__, __LINE__,LOCAL_ActiveSignals,YENV,ENV,ASP);
+#endif
   check_alarm_fail_int( FALSE PASS_REGS );
   /* don't do debugging and stack expansion here: space will
      be recovered. automatically by fail, so
@@ -817,6 +824,10 @@ interrupt_execute( USES_REGS1 )
 {
   int v;
   
+#ifdef DEBUG_INTERRUPTS
+  fprintf(stderr,"[%d] %s:%d: INTERRUPT %lx (YENV=%p ENV=%p ASP=%p)\n",  (int)pthread_self(), \
+	  __FUNCTION__, __LINE__,LOCAL_ActiveSignals,YENV,ENV,ASP);
+#endif
   check_alarm_fail_int( TRUE PASS_REGS );
   PP  = P->u.pp.p0;
   if ((PP->ExtraPredFlags & NoDebugPredFlag) && (LOCAL_ActiveSignals == YAP_CREEP_SIGNAL))
@@ -833,6 +844,10 @@ interrupt_call( USES_REGS1 )
 {
   int v;
   
+#ifdef DEBUG_INTERRUPTS
+  fprintf(stderr,"[%d] %s:%d: INTERRUPT %lx (YENV=%p ENV=%p ASP=%p)\n",  (int)pthread_self(), \
+	  __FUNCTION__, __LINE__,LOCAL_ActiveSignals,YENV,ENV,ASP);
+#endif
   check_alarm_fail_int( TRUE PASS_REGS );
   //  printf("%lx %p %p %lx\n", LOCAL_ActiveSignals, P->u.Osbpp.p, P->u.Osbpp.p0, P->u.Osbpp.p0->ExtraPredFlags);
   PP = P->u.Osbpp.p0;
@@ -850,6 +865,10 @@ interrupt_pexecute( PredEntry *pen USES_REGS )
 {
   int v;
 
+#ifdef DEBUG_INTERRUPTS
+  fprintf(stderr,"[%d] %s:%d: INTERRUPT %lx (YENV=%p ENV=%p ASP=%p)\n",  (int)pthread_self(), \
+	  __FUNCTION__, __LINE__,LOCAL_ActiveSignals,YENV,ENV,ASP);
+#endif
   check_alarm_fail_int( 2 PASS_REGS );
   PP = NULL;
   if (LOCAL_ActiveSignals == YAP_CREEP_SIGNAL)
@@ -875,6 +894,10 @@ interrupt_deallocate( USES_REGS1 )
 {
   int v;
   
+#ifdef DEBUG_INTERRUPTS
+  fprintf(stderr,"[%d] %s:%d: INTERRUPT %lx (YENV=%p ENV=%p ASP=%p)\n",  (int)pthread_self(), \
+	  __FUNCTION__, __LINE__,LOCAL_ActiveSignals,YENV,ENV,ASP);
+#endif
   check_alarm_fail_int( TRUE PASS_REGS );
   /* 
      don't do a creep here; also, if our instruction is followed by
@@ -918,6 +941,10 @@ interrupt_deallocate( USES_REGS1 )
 static int
 interrupt_cut( USES_REGS1 )
 {
+#ifdef DEBUG_INTERRUPTS
+  fprintf(stderr,"[%d] %s:%d: INTERRUPT %lx (YENV=%p ENV=%p ASP=%p)\n",  (int)pthread_self(), \
+	  __FUNCTION__, __LINE__,LOCAL_ActiveSignals,YENV,ENV,ASP);
+#endif
   check_alarm_fail_int( 2 PASS_REGS );
   if (!LOCAL_ActiveSignals || (LOCAL_ActiveSignals & (YAP_CDOVF_SIGNAL|YAP_CREEP_SIGNAL)) == LOCAL_ActiveSignals) {
     return 2;
@@ -932,6 +959,10 @@ interrupt_cut( USES_REGS1 )
 static int
 interrupt_cut_t( USES_REGS1 )
 {
+#ifdef DEBUG_INTERRUPTS
+  fprintf(stderr,"[%d] %s:%d: INTERRUPT %lx (YENV=%p ENV=%p ASP=%p)\n",  (int)pthread_self(), \
+	  __FUNCTION__, __LINE__,LOCAL_ActiveSignals,YENV,ENV,ASP);
+#endif
   check_alarm_fail_int( 2 PASS_REGS );
   if (!LOCAL_ActiveSignals || (LOCAL_ActiveSignals & (YAP_CDOVF_SIGNAL|YAP_CREEP_SIGNAL)) == LOCAL_ActiveSignals) {
     return 2;
@@ -946,7 +977,10 @@ interrupt_cut_t( USES_REGS1 )
 static int
 interrupt_commit_y( USES_REGS1 )
 {
-  check_alarm_fail_int( 2 PASS_REGS );
+#ifdef DEBUG_INTERRUPTS
+  fprintf(stderr,"[%d] %s:%d: INTERRUPT %lx (YENV=%p ENV=%p ASP=%p)\n",  (int)pthread_self(), \
+	  __FUNCTION__, __LINE__,LOCAL_ActiveSignals,YENV,ENV,ASP);
+#endif
   if (!LOCAL_ActiveSignals || (LOCAL_ActiveSignals & (YAP_CDOVF_SIGNAL|YAP_CREEP_SIGNAL)) == LOCAL_ActiveSignals) {
     return 2;
   }
@@ -960,6 +994,10 @@ interrupt_commit_y( USES_REGS1 )
 static int
 interrupt_commit_x( USES_REGS1 )
 {
+#ifdef DEBUG_INTERRUPTS
+  fprintf(stderr,"[%d] %s:%d: INTERRUPT %lx (YENV=%p ENV=%p ASP=%p)\n",  (int)pthread_self(), \
+	  __FUNCTION__, __LINE__,LOCAL_ActiveSignals,YENV,ENV,ASP);
+#endif
   check_alarm_fail_int( 2 PASS_REGS );
   if (!LOCAL_ActiveSignals || (LOCAL_ActiveSignals & (YAP_CDOVF_SIGNAL|YAP_CREEP_SIGNAL)) == LOCAL_ActiveSignals) {
     return 2;
@@ -987,6 +1025,10 @@ interrupt_either( USES_REGS1 )
 {
   int v;
   
+#ifdef DEBUG_INTERRUPTS
+  fprintf(stderr,"[%d] %s:%d: INTERRUPT %lx (YENV=%p ENV=%p ASP=%p)\n",  (int)pthread_self(), \
+	  __FUNCTION__, __LINE__,LOCAL_ActiveSignals,YENV,ENV,ASP);
+#endif
   check_alarm_fail_int( 2 PASS_REGS );
   if (LOCAL_ActiveSignals == YAP_CREEP_SIGNAL)
     return 2;
@@ -1006,6 +1048,10 @@ interrupt_dexecute( USES_REGS1 )
 {
   int v;
 
+#ifdef DEBUG_INTERRUPTS
+  fprintf(stderr,"[%d] %s:%d: INTERRUPT %lx (YENV=%p ENV=%p ASP=%p)\n",  (int)pthread_self(), \
+	  __FUNCTION__, __LINE__,LOCAL_ActiveSignals,YENV,ENV,ASP);
+#endif
   check_alarm_fail_int( 2 PASS_REGS );
   PP = P->u.pp.p0;
   if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL &&
@@ -3009,9 +3055,15 @@ Yap_absmi(int inp)
 #ifdef COROUTINING
     NoStackFail:
       BEGD(d0);
+#ifdef SHADOW_S
+      Yap_REGS.S_ = SREG;
+#endif
       saveregs();
       d0 = interrupt_fail( PASS_REGS1 );
       setregs();
+#ifdef SHADOW_S
+      SREG = Yap_REGS.S_;
+#endif
       if (!d0) FAIL();
       JMPNext();
       ENDD(d0);
@@ -3480,9 +3532,15 @@ Yap_absmi(int inp)
 
     NoStackDeallocate:
       BEGD(d0);
+#ifdef SHADOW_S
+      Yap_REGS.S_ = SREG;
+#endif
       saveregs();
       d0 = interrupt_deallocate( PASS_REGS1 );
       setregs();
+#ifdef SHADOW_S
+      SREG = Yap_REGS.S_;
+#endif
       if (!d0) FAIL();
       JMPNext();
       ENDD(d0);
@@ -13648,9 +13706,15 @@ Yap_absmi(int inp)
 	/* at this point, we have the arguments all set in the argument registers, pen says who is the current predicate. don't remove. */
       NoStackPExecute:
 	WRITEBACK_Y_AS_ENV();
+#ifdef SHADOW_S
+      Yap_REGS.S_ = SREG;
+#endif
 	saveregs();
 	d0 = interrupt_pexecute( pen PASS_REGS );
 	setregs();
+#ifdef SHADOW_S
+      SREG = Yap_REGS.S_;
+#endif
 	if (!d0) FAIL();
 	if (d0 == 2) goto execute_stack_checked;
 	goto execute_end;
diff --git a/C/tracer.c b/C/tracer.c
index d5d6044b9..7b314636f 100644
--- a/C/tracer.c
+++ b/C/tracer.c
@@ -159,7 +159,6 @@ low_level_trace(yap_low_level_port port, PredEntry *pred, CELL *args)
     gc_ENV = (CELL *) gc_ENV[E_E];	/* link to prev
 					 * environment */
   }
-  UNLOCK(Yap_heap_regs->low_level_trace_lock);
   return;
   {
     choiceptr b_p = B;
diff --git a/H/absmi.h b/H/absmi.h
index b835d6a4f..d1ee33137 100644
--- a/H/absmi.h
+++ b/H/absmi.h
@@ -1607,6 +1607,19 @@ void SET_ASP__(CELL *yreg, Int sz USES_REGS) {
      }
 
 
+#ifdef SHADOW_S
+#define PROCESS_INT( F, C ) \
+      BEGD(d0); \
+      Yap_REGS.S_ = SREG; \
+      saveregs(); \
+      d0 = F ( PASS_REGS1 );\
+      setregs(); \
+      SREG = Yap_REGS.S_; \
+      if (!d0) FAIL(); \
+      if (d0 == 2) goto C; \
+      JMPNext(); \
+      ENDD(d0);
+#else
 #define PROCESS_INT( F, C ) \
       BEGD(d0); \
       saveregs(); \
@@ -1616,4 +1629,5 @@ void SET_ASP__(CELL *yreg, Int sz USES_REGS) {
       if (d0 == 2) goto C; \
       JMPNext(); \
       ENDD(d0);
+#endif
 
diff --git a/library/dialect/swi/fli/swi.c b/library/dialect/swi/fli/swi.c
index 725afbe88..95c94568e 100755
--- a/library/dialect/swi/fli/swi.c
+++ b/library/dialect/swi/fli/swi.c
@@ -2291,7 +2291,7 @@ X_API void PL_register_foreign_in_module(const char *module, const char *name, i
   Int nflags = 0;
 
 #ifdef DEBUG
-  if (flags & (PL_FA_NOTRACE|PL_FA_CREF)) {
+  if (flags & (PL_FA_CREF)) {
     fprintf(stderr,"PL_register_foreign_in_module called with non-implemented flag %x when creating predicate %s:%s/%d\n", flags, module, name, arity);
   }      
 #endif