Index: sys/kern/kern_synch.c
===================================================================
RCS file: /cvsroot/src/sys/kern/kern_synch.c,v
retrieving revision 1.309
diff -u -r1.309 kern_synch.c
--- sys/kern/kern_synch.c	13 Oct 2015 00:25:51 -0000	1.309
+++ sys/kern/kern_synch.c	5 Mar 2016 20:51:16 -0000
@@ -277,6 +277,7 @@
 	KASSERT(lwp_locked(l, l->l_cpu->ci_schedstate.spc_lwplock));
 	KASSERT(l->l_stat == LSONPROC);
 	l->l_kpriority = false;
+	/*printf("yield() before mi_switch()\n");	*/
 	(void)mi_switch(l);
 	KERNEL_LOCK(l->l_biglocks, l);
 }
@@ -296,6 +297,7 @@
 	KASSERT(l->l_stat == LSONPROC);
 	l->l_kpriority = false;
 	l->l_nivcsw++;
+	/*printf("preempt() before mi_switch()\n");*/
 	(void)mi_switch(l);
 	KERNEL_LOCK(l->l_biglocks, l);
 }
@@ -376,6 +378,7 @@
 			kpreempt_ev_immed.ev_count++;
 		}
 		lwp_lock(l);
+		/*printf("kpreempt() before mi_switch()\n");*/
 		mi_switch(l);
 		l->l_nopreempt++;
 		splx(s);
@@ -506,6 +509,9 @@
 int
 mi_switch(lwp_t *l)
 {
+#if 1
+printf("mi_switch() %p (%s)\n", (void*)l, l->l_name);
+#endif 
 	struct cpu_info *ci;
 	struct schedstate_percpu *spc;
 	struct lwp *newl;
@@ -716,7 +722,38 @@
 		KASSERT(curlwp == ci->ci_curlwp);
 #endif
 		KASSERTMSG(l == curlwp, "l %p curlwp %p", l, curlwp);
+#if 1		
+printf("mi_switch() %p before cpu_switchto() from %s to %s\n", (void*)newl, l->l_name, newl->l_name);
+#endif 
+#if 1
+ struct pcb* opcb = (struct pcb*)l->l_addr;
+printf("mi_switch() l->l_pcb %p\n", (void*)opcb);
+ struct pcb* pcb = (struct pcb*)newl->l_addr;
+printf("mi_switch() newl->l_pcb %p\n", (void*)pcb);
+#if 0 
+ unsigned char* tmp = (unsigned char*)pcb; 
+ for (int i=0; i < USPACE; i++) {
+	 if ( i % 32 == 0 )
+		 printf("\n%p  ", (void*)(tmp+i));
+	 printf("%02x ", tmp[i]);
+ }
+ printf("\n");
+#endif 
+printf("mi_switch() newl->l_pcb->pcb_sp %lx\n", (long unsigned int)pcb->pcb_sp);
+printf("mi_switch() newl->l_pcb->pcb_pc %lx\n", (long unsigned int)pcb->pcb_pc);
+#if 0
+ Debugger();
+#endif
+#endif 
 		prevlwp = cpu_switchto(l, newl, returning);
+#if 0		
+#if 1
+ Debugger();
+#endif
+#if 0 
+printf("mi_switch() %p after cpu_switchto()\n", (void*)newl);
+#endif 
+#endif 
 		ci = curcpu();
 #ifdef MULTIPROCESSOR
 		KASSERT(curlwp == ci->ci_curlwp);
@@ -729,8 +766,8 @@
 		 * Restore VM context and IPL.
 		 */
 		pmap_activate(l);
-		uvm_emap_switch(l);
-		pcu_switchpoint(l);
+		uvm_emap_switch(l);  /* FIXME check this for sun4v */
+		pcu_switchpoint(l);  /* FIXME check this for sun4v */
 
 		if (prevlwp != NULL) {
 			/* Normalize the count of the spin-mutexes */