Partially revert previous commit. Calling getit() unconditionally fixed

a problem that could also be fixed differently without reverting previous
attempts to fix DELAY while the debugger is active (rev 1.204). The bug
was that the i8254 implements a countdown timer, while for (k)db_active
a countup timer was implemented. This resulted in premature termination
and consequently the breakage of DELAY. The fix (relative to rev 1.211)
is to implement a countdown timer for the kdb_active case. As such the
ability to step clock initialization is preserved and DELAY does what is
expected of it.

Blushed: bde :-)
Submitted by: bde

2 files changed, 44 insertions, 22 deletions

diff --git a/sys/i386/isa/clock.c b/sys/i386/isa/clock.c
index d4742598c350..1c82ffa90309 100644
--- a/sys/i386/isa/clock.c
+++ b/sys/i386/isa/clock.c
@@ -401,10 +401,7 @@ getit(void)
 {
 	int high, low;
 
-#ifdef KDB
-	if (!kdb_active)
-#endif
-		mtx_lock_spin(&clock_lock);
+	mtx_lock_spin(&clock_lock);
 
 	/* Select timer0 and latch counter value. */
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
@@ -412,11 +409,7 @@ getit(void)
 	low = inb(TIMER_CNTR0);
 	high = inb(TIMER_CNTR0);
 
-#ifdef KDB
-	if (!kdb_active)
-#endif
-		mtx_unlock_spin(&clock_lock);
-
+	mtx_unlock_spin(&clock_lock);
 	return ((high << 8) | low);
 }
 
@@ -457,8 +450,18 @@ DELAY(int n)
 	 * takes about 1.5 usec for each of the i/o's in getit().  The loop
 	 * takes about 6 usec on a 486/33 and 13 usec on a 386/20.  The
 	 * multiplications and divisions to scale the count take a while).
+	 *
+	 * However, if ddb is active then use a fake counter since reading
+	 * the i8254 counter involves acquiring a lock.  ddb must not do
+	 * locking for many reasons, but it calls here for at least atkbd
+	 * input.
 	 */
-	prev_tick = getit();
+#ifdef KDB
+	if (kdb_active)
+		prev_tick = 1;
+	else
+#endif
+		prev_tick = getit();
 	n -= 0;			/* XXX actually guess no initial overhead */
 	/*
 	 * Calculate (n * (timer_freq / 1e6)) without using floating point
@@ -485,7 +488,15 @@ DELAY(int n)
 			     / 1000000;
 
 	while (ticks_left > 0) {
-		tick = getit();
+#ifdef KDB
+		if (kdb_active) {
+			inb(0x84);
+			tick = prev_tick - 1;
+			if (tick <= 0)
+				tick = timer0_max_count;
+		} else
+#endif
+			tick = getit();
 #ifdef DELAYDEBUG
 		++getit_calls;
 #endif
diff --git a/sys/isa/atrtc.c b/sys/isa/atrtc.c
index d4742598c350..1c82ffa90309 100644
--- a/sys/isa/atrtc.c
+++ b/sys/isa/atrtc.c
@@ -401,10 +401,7 @@ getit(void)
 {
 	int high, low;
 
-#ifdef KDB
-	if (!kdb_active)
-#endif
-		mtx_lock_spin(&clock_lock);
+	mtx_lock_spin(&clock_lock);
 
 	/* Select timer0 and latch counter value. */
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
@@ -412,11 +409,7 @@ getit(void)
 	low = inb(TIMER_CNTR0);
 	high = inb(TIMER_CNTR0);
 
-#ifdef KDB
-	if (!kdb_active)
-#endif
-		mtx_unlock_spin(&clock_lock);
-
+	mtx_unlock_spin(&clock_lock);
 	return ((high << 8) | low);
 }
 
@@ -457,8 +450,18 @@ DELAY(int n)
 	 * takes about 1.5 usec for each of the i/o's in getit().  The loop
 	 * takes about 6 usec on a 486/33 and 13 usec on a 386/20.  The
 	 * multiplications and divisions to scale the count take a while).
+	 *
+	 * However, if ddb is active then use a fake counter since reading
+	 * the i8254 counter involves acquiring a lock.  ddb must not do
+	 * locking for many reasons, but it calls here for at least atkbd
+	 * input.
 	 */
-	prev_tick = getit();
+#ifdef KDB
+	if (kdb_active)
+		prev_tick = 1;
+	else
+#endif
+		prev_tick = getit();
 	n -= 0;			/* XXX actually guess no initial overhead */
 	/*
 	 * Calculate (n * (timer_freq / 1e6)) without using floating point
@@ -485,7 +488,15 @@ DELAY(int n)
 			     / 1000000;
 
 	while (ticks_left > 0) {
-		tick = getit();
+#ifdef KDB
+		if (kdb_active) {
+			inb(0x84);
+			tick = prev_tick - 1;
+			if (tick <= 0)
+				tick = timer0_max_count;
+		} else
+#endif
+			tick = getit();
 #ifdef DELAYDEBUG
 		++getit_calls;
 #endif