[PATCH] libata: implement ata_poll_qc_complete and use it in polling functions

[PATCH libata-dev-2.6:upstream] implement ata_poll_qc_complete and use it in polling functions

 Previously, libata polling functions turned irq back on and completed
qc commands without holding host lock.  This creates a race condition
between the polling task and interrupts from other ports on the same
host set or spurious interrupt from itself.

 This patch implements ata_poll_qc_complete which enables irq and
completes qc atomically and convert all polling functions.

 Note: atapi_packet_task() didn't use to turn irq back on or clear
ATA_FLAG_NOINTR on error exits.  This patch makes it use
ata_poll_qc_complete which does both.

 Note: With this change, ALL invocations of ata_qc_complete() are now
done under host_set lock.

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

1 files changed, 24 insertions, 10 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index c92439fe5dae..2f68563ac3a3 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -2402,6 +2402,26 @@ static int ata_sg_setup(struct ata_queued_cmd *qc)
 }
 
 /**
+ *      ata_poll_qc_complete - turn irq back on and finish qc
+ *      @qc: Command to complete
+ *      @drv_stat: ATA status register content
+ *
+ *      LOCKING:
+ *      None.  (grabs host lock)
+ */
+
+void ata_poll_qc_complete(struct ata_queued_cmd *qc, u8 drv_stat)
+{
+        struct ata_port *ap = qc->ap;
+
+        spin_lock_irq(&ap->host_set->lock);
+        ap->flags &= ~ATA_FLAG_NOINTR;
+        ata_irq_on(ap);
+        ata_qc_complete(qc, drv_stat);
+        spin_unlock_irq(&ap->host_set->lock);
+}
+
+/**
  *      ata_pio_poll -
  *      @ap:
  *
@@ -2492,9 +2512,7 @@ static void ata_pio_complete (struct ata_port *ap)
 
         ap->pio_task_state = PIO_ST_IDLE;
 
-        ata_irq_on(ap);
-
-        ata_qc_complete(qc, drv_stat);
+        ata_poll_qc_complete(qc, drv_stat);
 }
 
 
@@ -2844,9 +2862,7 @@ static void ata_pio_block(struct ata_port *ap)
                 if ((status & ATA_DRQ) == 0) {
                         ap->pio_task_state = PIO_ST_IDLE;
 
-                        ata_irq_on(ap);
-
-                        ata_qc_complete(qc, status);
+                        ata_poll_qc_complete(qc, status);
                         return;
                 }
 
@@ -2876,9 +2892,7 @@ static void ata_pio_error(struct ata_port *ap)
 
         ap->pio_task_state = PIO_ST_IDLE;
 
-        ata_irq_on(ap);
-
-        ata_qc_complete(qc, drv_stat | ATA_ERR);
+        ata_poll_qc_complete(qc, drv_stat | ATA_ERR);
 }
 
 static void ata_pio_task(void *_data)
@@ -3791,7 +3805,7 @@ static void atapi_packet_task(void *_data)
         return;
 
 err_out:
-        ata_qc_complete(qc, ATA_ERR);
+        ata_poll_qc_complete(qc, ATA_ERR);
 }