[PATCH 045/145] [SCSI] aacraid: Fix for arrays are going offline in the system. System hangs

[Kamal Mostafa]

3.8.13.5 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mahesh Rajashekhara <Mahesh.Rajashekhara at pmcs.com>

commit c5bebd829dd95602c15f8da8cc50fa938b5e0254 upstream.

One of the customer had reported that the set of raid logical arrays will
become unavailable (I/O offline) after a long hours of IO stress test.  The OS
wouldn`t be accessible afterwards and require a hard reset.

This driver patch has a fix for race condition between the doorbell and the
circular buffer. The driver is modified to do an extra read after clearing the
doorbell in case there had been a completion posted during the small timing
window.

With this fix, we ran IO stress for ~13 days. There were no IO failures.

Signed-off-by: Mahesh Rajashekhara <Mahesh.Rajashekhara at pmcs.com>
Signed-off-by: James Bottomley <JBottomley at Parallels.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/scsi/aacraid/src.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/scsi/aacraid/src.c b/drivers/scsi/aacraid/src.c
index 3b021ec..e34418f 100644
--- a/drivers/scsi/aacraid/src.c
+++ b/drivers/scsi/aacraid/src.c
@@ -93,6 +93,9 @@ static irqreturn_t aac_src_intr_message(int irq, void *dev_id)
 			int send_it = 0;
 			extern int aac_sync_mode;
 
+			src_writel(dev, MUnit.ODR_C, bellbits);
+			src_readl(dev, MUnit.ODR_C);
+
 			if (!aac_sync_mode) {
 				src_writel(dev, MUnit.ODR_C, bellbits);
 				src_readl(dev, MUnit.ODR_C);
-- 
1.8.1.2