On 12/22/2015 02:18 AM, Finn Thain wrote:
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 <fthain@xxxxxxxxxxxxxxxxxxx> --- Changed since v2: - Moved max_sectors initialization to wrapper drivers. It isn't really relevant to the core driver and compile-time configuration using macros like REAL_DMA should be avoided. --- drivers/scsi/NCR5380.c | 6 ++++-- drivers/scsi/arm/cumana_1.c | 1 + drivers/scsi/arm/oak.c | 1 + drivers/scsi/atari_NCR5380.c | 6 ++++-- drivers/scsi/dmx3191d.c | 1 + drivers/scsi/dtc.c | 1 + drivers/scsi/g_NCR5380.c | 1 + drivers/scsi/mac_scsi.c | 1 + drivers/scsi/pas16.c | 1 + drivers/scsi/t128.c | 1 + 10 files changed, 16 insertions(+), 4 deletions(-)
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