MFi386: machdep.c:1.570 clock.c:1.204 by bde: Quick fix for calling DELAY

for ddb input in some atkbd-based console drivers.  ddb must not use any
normal locks but DELAY() normally calls getit() which needs clock_lock.
This also removes the need for recursion on clock_lock.

2 files changed, 19 insertions, 3 deletions

diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 86fff6c..1f5948b 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -1166,7 +1166,7 @@ hammer_time(u_int64_t modulep, u_int64_t physfree)
 	 *	     under witness.
 	 */
 	mutex_init();
-	mtx_init(&clock_lock, "clk", NULL, MTX_SPIN | MTX_RECURSE);
+	mtx_init(&clock_lock, "clk", NULL, MTX_SPIN);
 	mtx_init(&icu_lock, "icu", NULL, MTX_SPIN | MTX_NOWITNESS);
 
 	/* exceptions */
diff --git a/sys/amd64/isa/clock.c b/sys/amd64/isa/clock.c
index 2ed1544..c88e488 100644
--- a/sys/amd64/isa/clock.c
+++ b/sys/amd64/isa/clock.c
@@ -413,8 +413,18 @@ 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 go
+	 * locking for many reasons, but it calls here for at least atkbd
+	 * input.
 	 */
-	prev_tick = getit();
+#ifdef DDB
+	if (db_active)
+		prev_tick = 0;
+	else
+#endif
+		prev_tick = getit();
 	n -= 0;			/* XXX actually guess no initial overhead */
 	/*
 	 * Calculate (n * (timer_freq / 1e6)) without using floating point
@@ -441,7 +451,13 @@ DELAY(int n)
 			     / 1000000;
 
 	while (ticks_left > 0) {
-		tick = getit();
+#ifdef DDB
+		if (db_active) {
+			inb(0x84);
+			tick = prev_tick + 1;
+		} else
+#endif
+			tick = getit();
 #ifdef DELAYDEBUG
 		++getit_calls;
 #endif