[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Pine.LNX.4.44L0.0908031142180.16208-100000@iolanthe.rowland.org>
Date: Mon, 3 Aug 2009 11:45:26 -0400 (EDT)
From: Alan Stern <stern@...land.harvard.edu>
To: Artur Skawina <art.08.09@...il.com>
cc: "Lev A. Melnikovsky" <melnikovsky@...l.ru>,
Linux Kernel <linux-kernel@...r.kernel.org>,
<linux-usb@...r.kernel.org>
Subject: Re: reading errors on JMicron JM20337 USB-SATA
On Mon, 3 Aug 2009, Artur Skawina wrote:
> > You are correct except for the term "indefinitely". The retries _will_
> > stop if you wait long enough. Unfortunately, because of all the nested
> > retry loops in the SCSI drivers and at the application level, you may
> > have to wait as long as half an hour.
>
> iirc, i had stalls _way_ longer than that, probably because the reads
> eventually succeeded, only to stall on the next ones.
>
> > I agree that this should be fixed. But it is a SCSI issue, not a USB
> > issue. You could try bringing it up on the linux-scsi mailing list.
>
> actually, the number of retries should probably be configurable, but i
> wouldn't lower them by default; losing data because of recoverable errors
> is bad. In this case the bridge may be at fault (by not passing along the
> error), but to make a significant difference you'd have to reduce the number
> of retries to something like zero, maybe one at most, and that's just too
> low for a default.
As I understand it, the SCSI and block layers conspire to keep retrying
each command until a timeout expires, not until the number of retries
reaches a limit.
But the situation is complicated, because some kinds of retries reset
the timer. And if the application repeats the I/O request then of
course everything starts over again.
Alan Stern
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists