[PATCH] fix atapi_packet_task vs. intr race (take 2)

Interrupts from devices sharing the same IRQ could cause
ata_host_intr to finish commands being processed by atapi_packet_task
if the commands are using ATA_PROT_ATAPI_NODATA or ATA_PROT_ATAPI_DMA
protocol.  This is because libata interrupt handler is unaware that
interrupts are not expected during that period.  This patch adds
ATA_FLAG_NOINTR flag to tell the interrupt handler that we're not
expecting interrupts.

 Note that once proper HSM is implemented for interrupt-driven PIO,
this should be merged into it and this flag will be removed.

 ahci.c is a different kind of beast, so it's left alone.

* The following drivers use ata_qc_issue_prot and ata_interrupt, so
  changes in libata core will do.

  ata_piix sata_sil sata_svw sata_via sata_sis sata_uli

* The following drivers use ata_qc_issue_prot and custom intr handler.
  They need this change to work correctly.

  sata_nv sata_vsc

* The following drivers use custom issue function and intr handler.
  Currently all custom issue functions don't support ATAPI, so this
  change is irrelevant, updated for consistency and to avoid later
  mistakes.

  sata_promise sata_qstor sata_sx4

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>

1 files changed, 22 insertions, 11 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 9a6aacf467b8..c92439fe5dae 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -3350,11 +3350,13 @@ int ata_qc_issue_prot(struct ata_queued_cmd *qc)
 		break;
 
 	case ATA_PROT_ATAPI_NODATA:
+		ap->flags |= ATA_FLAG_NOINTR;
 		ata_tf_to_host_nolock(ap, &qc->tf);
 		queue_work(ata_wq, &ap->packet_task);
 		break;
 
 	case ATA_PROT_ATAPI_DMA:
+		ap->flags |= ATA_FLAG_NOINTR;
 		ap->ops->tf_load(ap, &qc->tf);	 /* load tf registers */
 		ap->ops->bmdma_setup(qc);	    /* set up bmdma */
 		queue_work(ata_wq, &ap->packet_task);
@@ -3708,7 +3710,8 @@ irqreturn_t ata_interrupt (int irq, void *dev_instance, struct pt_regs *regs)
 		struct ata_port *ap;
 
 		ap = host_set->ports[i];
-		if (ap && (!(ap->flags & ATA_FLAG_PORT_DISABLED))) {
+		if (ap &&
+		    !(ap->flags & (ATA_FLAG_PORT_DISABLED | ATA_FLAG_NOINTR))) {
 			struct ata_queued_cmd *qc;
 
 			qc = ata_qc_from_tag(ap, ap->active_tag);
@@ -3760,19 +3763,27 @@ static void atapi_packet_task(void *_data)
 	/* send SCSI cdb */
 	DPRINTK("send cdb\n");
 	assert(ap->cdb_len >= 12);
-	ata_data_xfer(ap, qc->cdb, ap->cdb_len, 1);
 
-	/* if we are DMA'ing, irq handler takes over from here */
-	if (qc->tf.protocol == ATA_PROT_ATAPI_DMA)
-		ap->ops->bmdma_start(qc);	    /* initiate bmdma */
+	if (qc->tf.protocol == ATA_PROT_ATAPI_DMA ||
+	    qc->tf.protocol == ATA_PROT_ATAPI_NODATA) {
+		unsigned long flags;
 
-	/* non-data commands are also handled via irq */
-	else if (qc->tf.protocol == ATA_PROT_ATAPI_NODATA) {
-		/* do nothing */
-	}
+		/* Once we're done issuing command and kicking bmdma,
+		 * irq handler takes over.  To not lose irq, we need
+		 * to clear NOINTR flag before sending cdb, but
+		 * interrupt handler shouldn't be invoked before we're
+		 * finished.  Hence, the following locking.
+		 */
+		spin_lock_irqsave(&ap->host_set->lock, flags);
+		ap->flags &= ~ATA_FLAG_NOINTR;
+		ata_data_xfer(ap, qc->cdb, ap->cdb_len, 1);
+		if (qc->tf.protocol == ATA_PROT_ATAPI_DMA)
+			ap->ops->bmdma_start(qc);	/* initiate bmdma */
+		spin_unlock_irqrestore(&ap->host_set->lock, flags);
+	} else {
+		ata_data_xfer(ap, qc->cdb, ap->cdb_len, 1);
 
-	/* PIO commands are handled by polling */
-	else {
+		/* PIO commands are handled by polling */
 		ap->pio_task_state = PIO_ST;
 		queue_work(ata_wq, &ap->pio_task);
 	}