Index: sys/kern/kern_tc.c
===================================================================
--- sys/kern/kern_tc.c	(revision 223446)
+++ sys/kern/kern_tc.c	(working copy)
@@ -492,6 +492,12 @@ tc_windup(void)
 
 	/* Now is a good time to change timecounters. */
 	if (th->th_counter != timecounter) {
+#if !defined(__arm__) && !defined(__ia64__)
+		if ((timecounter->tc_flags & TC_FLAGS_C3STOP) != 0)
+			cpu_disable_deep_sleep++;
+		if ((th->th_counter->tc_flags & TC_FLAGS_C3STOP) != 0)
+			cpu_disable_deep_sleep--;
+#endif
 		th->th_counter = timecounter;
 		th->th_offset_count = ncount;
 		tc_min_ticktock_freq = max(1, timecounter->tc_frequency /
Index: sys/sparc64/sparc64/counter.c
===================================================================
--- sys/sparc64/sparc64/counter.c	(revision 223446)
+++ sys/sparc64/sparc64/counter.c	(working copy)
@@ -98,6 +98,7 @@ sparc64_counter_init(const char *name, bus_space_t
 	tc->tc_name = strdup(name, M_DEVBUF);
 	tc->tc_priv = sc;
 	tc->tc_quality = COUNTER_QUALITY;
+	tc->tc_flags = 0;
 	tc_init(tc);
 }
 
Index: sys/sys/timetc.h
===================================================================
--- sys/sys/timetc.h	(revision 223446)
+++ sys/sys/timetc.h	(working copy)
@@ -57,6 +57,8 @@ struct timecounter {
 		 * another timecounter higher means better.  Negative
 		 * means "only use at explicit request".
 		 */
+	u_int			tc_flags;
+#define	TC_FLAGS_C3STOP		1	/* Timer dies in C3. */
 
 	void			*tc_priv;
 		/* Pointer to the timecounter's private parts. */
Index: sys/x86/x86/tsc.c
===================================================================
--- sys/x86/x86/tsc.c	(revision 223446)
+++ sys/x86/x86/tsc.c	(working copy)
@@ -452,6 +452,7 @@ init_TSC_tc(void)
 	if (cpu_can_deep_sleep && cpu_vendor_id == CPU_VENDOR_INTEL &&
 	    (amd_pminfo & AMDPM_TSC_INVARIANT) == 0) {
 		tsc_timecounter.tc_quality = -1000;
+		tsc_timecounter.tc_flags |= TC_FLAGS_C3STOP;
 		if (bootverbose)
 			printf("TSC timecounter disabled: C3 enabled.\n");
 		goto init;