Re: [PATCH v3 20/77] ncr5380: Introduce unbound workqueue

Hannes Reinecke
2015-12-22T07:10:46Z

On 12/22/2015 02:17 AM, Finn Thain wrote:
> Allocate a work queue that will permit busy waiting and sleeping. This
> means NCR5380_init() can potentially fail, so add this error path.
>
> Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
>
> ---
>
> In subsequent patches, the work function adopts this work queue so it
> can sleep while polling, which allows the removal of some flawed and
> complicated code in NCR5380_select() in NCR5380.c.
>
> Changed since v1:
> - Dropped WQ_CPU_INTENSIVE flag because Documentation/workqueue.txt says it
> "is meaningless for unbound wq".
>
> ---
> drivers/scsi/NCR5380.c | 15 +++++++++++----
> drivers/scsi/NCR5380.h | 1 +
> drivers/scsi/arm/cumana_1.c | 8 ++++++--
> drivers/scsi/arm/oak.c | 8 ++++++--
> drivers/scsi/atari_NCR5380.c | 8 +++++++-
> drivers/scsi/atari_scsi.c | 5 ++++-
> drivers/scsi/dmx3191d.c | 17 +++++++++++------
> drivers/scsi/dtc.c | 11 +++++++++--
> drivers/scsi/g_NCR5380.c | 31 +++++++++++++++----------------
> drivers/scsi/mac_scsi.c | 5 ++++-
> drivers/scsi/pas16.c | 10 ++++++++--
> drivers/scsi/sun3_scsi.c | 5 ++++-
> drivers/scsi/t128.c | 13 ++++++++++---
> 13 files changed, 96 insertions(+), 41 deletions(-)
>
> Index: linux/drivers/scsi/NCR5380.c
> ===================================================================
> --- linux.orig/drivers/scsi/NCR5380.c 2015-12-22 12:15:52.000000000 +1100
> +++ linux/drivers/scsi/NCR5380.c 2015-12-22 12:15:56.000000000 +1100
> @@ -514,7 +514,7 @@ static int should_disconnect(unsigned ch
> static void NCR5380_set_timer(struct NCR5380_hostdata *hostdata, unsigned long timeout)
> {
> hostdata->time_expires = jiffies + timeout;
> - schedule_delayed_work(&hostdata->coroutine, timeout);
> + queue_delayed_work(hostdata->work_q, &hostdata->coroutine, timeout);
> }
>
>
> @@ -791,7 +791,12 @@ static int NCR5380_init(struct Scsi_Host
> hostdata->disconnected_queue = NULL;
>
> INIT_DELAYED_WORK(&hostdata->coroutine, NCR5380_main);
> -
> + hostdata->work_q = alloc_workqueue("ncr5380_%d",
> + WQ_UNBOUND | WQ_MEM_RECLAIM,
> + 1, instance->host_no);
> + if (!hostdata->work_q)
> + return -ENOMEM;
> +
> /* The CHECK code seems to break the 53C400. Will check it later maybe */
> if (flags & FLAG_NCR53C400)
> hostdata->flags = FLAG_HAS_LAST_BYTE_SENT | flags;

Wouldn't it be better to use a normal (ie bound) workqueue here?
SCSI-2 is pretty much single-threaded, so shifting things onto arbitrary
CPUs don't sound very appealing.

Cheers,

Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@suse.de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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