From 0a4e36125451165847c6d4e7d5633d92e53f5c69 Mon Sep 17 00:00:00 2001 From: Finn Thain Date: Sun, 3 Jan 2016 16:06:07 +1100 Subject: ncr5380: Fix soft lockups Because of the rudimentary design of the chip, it is necessary to poll the SCSI bus signals during PIO and this tends to hog the CPU. The driver will accept new commands while others execute, and this causes a soft lockup because the workqueue item will not terminate until the issue queue is emptied. When exercising dmx3191d using sequential IO from dd, the driver is sent 512 KiB WRITE commands and 128 KiB READs. For a PIO transfer, the rate is is only about 300 KiB/s, so these are long-running commands. And although PDMA may run at several MiB/s, interrupts are disabled for the duration of the transfer. Fix the unresponsiveness and soft lockup issues by calling cond_resched() after each command is completed and by limiting max_sectors for drivers that don't implement real DMA. Signed-off-by: Finn Thain Reviewed-by: Hannes Reinecke Tested-by: Ondrej Zary Tested-by: Michael Schmitz Signed-off-by: Martin K. Petersen --- drivers/scsi/dtc.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/scsi/dtc.c') diff --git a/drivers/scsi/dtc.c b/drivers/scsi/dtc.c index f6166e34e3b0..6c736b071cf4 100644 --- a/drivers/scsi/dtc.c +++ b/drivers/scsi/dtc.c @@ -453,5 +453,6 @@ static struct scsi_host_template driver_template = { .cmd_per_lun = 2, .use_clustering = DISABLE_CLUSTERING, .cmd_size = NCR5380_CMD_SIZE, + .max_sectors = 128, }; #include "scsi_module.c" -- cgit v1.2.1