Take the plunge and make this driver be INTR_FAST. This re-arranges the

interrupt handler so that no locks are needed, and schedules the
command completion routine with a taskqueue_fast.  This also corrects the
locking in the command thread and removes the need for operation flags.

Simple load tests show that this is now considerably faster than FreeBSD 4.x
in the SMP case when multiple i/o tasks are running.

sys/dev/aac/aac.c

@@ -601,7 +601,6 @@ void
 aac_intr(void *arg)
 {
 	struct aac_softc *sc;
-	u_int32_t *resp_queue;
 	u_int16_t reason;
 
 	debug_called(2);
@@ -609,49 +608,37 @@ aac_intr(void *arg)
 	sc = (struct aac_softc *)arg;
 
 	/*
-	 * Optimize the common case of adapter response interrupts.
-	 * We must read from the card prior to processing the responses
-	 * to ensure the clear is flushed prior to accessing the queues.
-	 * Reading the queues from local memory might save us a PCI read.
+	 * Read the status register directly.  This is faster than taking the
+	 * driver lock and reading the queues directly.  It also saves having
+	 * to turn parts of the driver lock into a spin mutex, which would be
+	 * ugly.
 	 */
-	resp_queue = sc->aac_queues->qt_qindex[AAC_HOST_NORM_RESP_QUEUE];
-	if (resp_queue[AAC_PRODUCER_INDEX] != resp_queue[AAC_CONSUMER_INDEX])
-		reason = AAC_DB_RESPONSE_READY;
-	else 
 	reason = AAC_GET_ISTATUS(sc);
 	AAC_CLEAR_ISTATUS(sc, reason);
-	(void)AAC_GET_ISTATUS(sc);
 
-	/* It's not ok to return here because of races with the previous step */
-	if (reason & AAC_DB_RESPONSE_READY)
 	/* handle completion processing */
-		taskqueue_enqueue(taskqueue_swi, &sc->aac_task_complete);
+	if (reason & AAC_DB_RESPONSE_READY)
+		taskqueue_enqueue_fast(taskqueue_fast, &sc->aac_task_complete);
 
-	/* controller wants to talk to the log */
-	if (reason & AAC_DB_PRINTF) {
-		if (sc->aifflags & AAC_AIFFLAGS_RUNNING) {
-			sc->aifflags |= AAC_AIFFLAGS_PRINTF;
-		} else
-			aac_print_printf(sc);
-	}
-
-	/* controller has a message for us? */
-	if (reason & AAC_DB_COMMAND_READY) {
-		if (sc->aifflags & AAC_AIFFLAGS_RUNNING) {
-			sc->aifflags |= AAC_AIFFLAGS_AIF;
-		} else {
+	/* controller wants to talk to us */
+	if (reason & (AAC_DB_PRINTF | AAC_DB_COMMAND_READY)) {
 		/*
-			 * XXX If the kthread is dead and we're at this point,
-			 * there are bigger problems than just figuring out
-			 * what to do with an AIF.
+		 * XXX Make sure that we don't get fooled by strange messages
+		 * that start with a NULL.
 		 */
-		}
+		if ((reason & AAC_DB_PRINTF) &&
+		    (sc->aac_common->ac_printf[0] == 0))
+			sc->aac_common->ac_printf[0] = 32;
 
-	}
-
-	if ((sc->aifflags & AAC_AIFFLAGS_PENDING) != 0)
-		/* XXX Should this be done with cv_signal? */
+		/*
+		 * This might miss doing the actual wakeup.  However, the
+		 * tsleep that this is waking up has a timeout, so it will
+		 * wake up eventually.  AIFs and printfs are low enough
+		 * priority that they can handle hanging out for a few seconds
+		 * if needed.
+		 */
 		wakeup(sc->aifthread);
+	}
 }
 
 /*
@@ -740,41 +727,43 @@ aac_command_thread(struct aac_softc *sc)
 {
 	struct aac_fib *fib;
 	u_int32_t fib_size;
-	int size;
+	int size, retval;
 
 	debug_called(2);
 
 	sc->aifflags |= AAC_AIFFLAGS_RUNNING;
 
 	while (!(sc->aifflags & AAC_AIFFLAGS_EXIT)) {
-		if ((sc->aifflags & AAC_AIFFLAGS_PENDING) == 0)
-			tsleep(sc->aifthread, PRIBIO, "aifthd",
+		retval = tsleep(sc->aifthread, PRIBIO, "aifthd",
 				AAC_PERIODIC_INTERVAL * hz);
 
-		if ((sc->aifflags & AAC_AIFFLAGS_PENDING) == 0)
+		/*
+		 * First see if any FIBs need to be allocated.  This needs
+		 * to be called without the driver lock because contigmalloc
+		 * will grab Giant, and would result in an LOR.
+		 */
+		if ((sc->aifflags & AAC_AIFFLAGS_ALLOCFIBS) != 0) {
+			aac_alloc_commands(sc);
+			sc->aifflags &= ~AAC_AIFFLAGS_ALLOCFIBS;
+		}
+
+		AAC_LOCK_ACQUIRE(&sc->aac_io_lock);
+
+		/*
+		 * While we're here, check to see if any commands are stuck.
+		 * This is pretty low-priority, so it's ok if it doesn't
+		 * always fire.
+		 */
+		if (retval == EWOULDBLOCK)
 			aac_timeout(sc);
 
 		/* Check the hardware printf message buffer */
-		if ((sc->aifflags & AAC_AIFFLAGS_PRINTF) != 0) {
-			sc->aifflags &= ~AAC_AIFFLAGS_PRINTF;
+		if (sc->aac_common->ac_printf[0] != 0)
 			aac_print_printf(sc);
-		}
 
-		/* See if any FIBs need to be allocated */
-		if ((sc->aifflags & AAC_AIFFLAGS_ALLOCFIBS) != 0) {
-			AAC_LOCK_ACQUIRE(&sc->aac_io_lock);
-			aac_alloc_commands(sc);
-			sc->aifflags &= ~AAC_AIFFLAGS_ALLOCFIBS;
-			AAC_LOCK_RELEASE(&sc->aac_io_lock);
-		}
-
-		/* While we're here, check to see if any commands are stuck */
-		while (sc->aifflags & AAC_AIFFLAGS_AIF) {
-			if (aac_dequeue_fib(sc, AAC_HOST_NORM_CMD_QUEUE,
-					    &fib_size, &fib)) {
-				sc->aifflags &= ~AAC_AIFFLAGS_AIF;
-				break;	/* nothing to do */
-			}
+		/* Also check to see if the adapter has a command for us. */
+		while (aac_dequeue_fib(sc, AAC_HOST_NORM_CMD_QUEUE,
+				       &fib_size, &fib) == 0) {
 	
 			AAC_PRINT_FIB(sc, fib);
 	
@@ -813,6 +802,7 @@ aac_command_thread(struct aac_softc *sc)
 						     fib);
 			}
 		}
+		AAC_LOCK_RELEASE(&sc->aac_io_lock);
 	}
 	sc->aifflags &= ~AAC_AIFFLAGS_RUNNING;
 	wakeup(sc->aac_dev);
@@ -1171,6 +1161,7 @@ aac_alloc_commands(struct aac_softc *sc)
 			      aac_map_command_helper, &fibphys, 0);
 
 	/* initialise constant fields in the command structure */
+	AAC_LOCK_ACQUIRE(&sc->aac_io_lock);
 	bzero(fm->aac_fibs, AAC_FIB_COUNT * sizeof(struct aac_fib));
 	for (i = 0; i < AAC_FIB_COUNT; i++) {
 		cm = sc->aac_commands + sc->total_fibs;
@@ -1191,9 +1182,11 @@ aac_alloc_commands(struct aac_softc *sc)
 	if (i > 0) {
 		TAILQ_INSERT_TAIL(&sc->aac_fibmap_tqh, fm, fm_link);
 		debug(1, "total_fibs= %d\n", sc->total_fibs);
+		AAC_LOCK_RELEASE(&sc->aac_io_lock);
 		return (0);
 	} 
 
+	AAC_LOCK_RELEASE(&sc->aac_io_lock);
 	bus_dmamap_unload(sc->aac_fib_dmat, fm->aac_fibmap);
 	bus_dmamem_free(sc->aac_fib_dmat, fm->aac_fibs, fm->aac_fibmap);
 	free(fm, M_AACBUF);

sys/dev/aac/aac_pci.c

@@ -224,7 +224,7 @@ aac_pci_attach(device_t dev)
 #define INTR_ENTROPY 0
 #endif
 	if (bus_setup_intr(sc->aac_dev, sc->aac_irq,
-			   INTR_MPSAFE|INTR_TYPE_BIO|INTR_ENTROPY, aac_intr,
+			   INTR_FAST|INTR_TYPE_BIO, aac_intr,
 			   sc, &sc->aac_intr)) {
 		device_printf(sc->aac_dev, "can't set up interrupt\n");
 		goto out;

sys/dev/aac/aacvar.h

@@ -572,5 +572,6 @@ aac_print_printf(struct aac_softc *sc)
 	 */
 	device_printf(sc->aac_dev, "**Monitor** %.*s", AAC_PRINTF_BUFSIZE,
 		      sc->aac_common->ac_printf);
+	sc->aac_common->ac_printf[0] = 0;
 	AAC_QNOTIFY(sc, AAC_DB_PRINTF);
 }