PERFORCE change 94252 for review

[Marcel Moolenaar]

http://perforce.freebsd.org/chv.cgi?CH=94252

Change 94252 by marcel at marcel_nfs on 2006/03/29 18:27:21

	Remove sc_schedih. It was used to limit calling
	swi_sched(), but introduced a race. Instead call
	swi_sched() on the 0 to !0 transition of the TTY
	pending interrupt status. Do this atomically.

Affected files ...

.. //depot/projects/uart/dev/uart/uart_bus.h#42 edit
.. //depot/projects/uart/dev/uart/uart_core.c#49 edit
.. //depot/projects/uart/dev/uart/uart_kbd_sun.c#8 edit
.. //depot/projects/uart/dev/uart/uart_tty.c#26 edit

Differences ...

==== //depot/projects/uart/dev/uart/uart_bus.h#42 (text+ko) ====

@@ -100,7 +100,6 @@
 	int		sc_opened:1;	/* This UART is open for business. */
 	int		sc_polled:1;	/* This UART has no interrupts. */
 	int		sc_txbusy:1;	/* This UART is transmitting. */
-	int		sc_schedih:1;	/* The softih needs (re)scheduling. */
 
 	struct uart_devinfo *sc_sysdev;	/* System device (or NULL). */
 

==== //depot/projects/uart/dev/uart/uart_core.c#49 (text+ko) ====

@@ -71,17 +71,21 @@
 }
 
 /*
- * Schedule a soft interrupt.
+ * Schedule a soft interrupt. We do this on the 0 to !0 transition
+ * of the TTY pending interrupt status.
  */
-static __inline void
+static void
 uart_sched_softih(struct uart_softc *sc, uint32_t ipend)
 {
+	uint32_t new, old;
+
+	do {
+		old = sc->sc_ttypend;
+		new = old | ipend;
+	} while (!atomic_cmpset_32(&sc->sc_ttypend, old, new));
 
-	atomic_set_32(&sc->sc_ttypend, ipend);
-	if (sc->sc_schedih) {
+	if (old == 0)
 		swi_sched(sc->sc_softih, 0);
-		sc->sc_schedih = 0;
-	}
 }
 
 /*

==== //depot/projects/uart/dev/uart/uart_kbd_sun.c#8 (text+ko) ====

@@ -258,7 +258,6 @@
 		    &sunkbd_softc, SWI_TTY, INTR_TYPE_TTY, &sc->sc_softih);
 
 		sc->sc_opened = 1;
-		sc->sc_schedih = 1;
 		KBD_INIT_DONE(&sunkbd_softc.sc_kbd);
 	}
 
@@ -274,7 +273,6 @@
 	if (sc->sc_uart->sc_leaving)
 		return;
 
-	sc->sc_uart->sc_schedih = 1;
 	pend = atomic_readandclear_32(&sc->sc_uart->sc_ttypend);
 	if (!(pend & SER_INT_MASK))
 		return;

==== //depot/projects/uart/dev/uart/uart_tty.c#26 (text+ko) ====

@@ -306,7 +306,6 @@
 	if (sc->sc_leaving)
 		return;
 
-	sc->sc_schedih = 1;
 	pend = atomic_readandclear_32(&sc->sc_ttypend);
 	if (!(pend & SER_INT_MASK))
 		return;
@@ -380,7 +379,6 @@
 
 	swi_add(&tty_intr_event, uart_driver_name, uart_tty_intr, sc, SWI_TTY,
 	    INTR_TYPE_TTY, &sc->sc_softih);
-	sc->sc_schedih = 1;
 
 	ttycreate(tp, TS_CALLOUT, "u%r", unit);