* [9fans] Bizarre freeze
@ 2008-08-05 18:01 sqweek
2008-08-05 18:16 ` Sape Mullender
0 siblings, 1 reply; 6+ messages in thread
From: sqweek @ 2008-08-05 18:01 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
Ran into an interesting one setting up my cpu server. The following
reliably freezes the box:
# echo dma on >/dev/sdC0/ctl
# 9fat:
Leaves the console totally unresponsive, no ^T^Tp, no ^P. rc -x on
9fat: gives "rfork e" as the final command.
sdC0 is a cdrom. I can turn dma on for my sata disks (sdE0/sdF0) no problem.
-sqweek
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] Bizarre freeze
2008-08-05 18:01 [9fans] Bizarre freeze sqweek
@ 2008-08-05 18:16 ` Sape Mullender
2008-08-05 18:26 ` ron minnich
0 siblings, 1 reply; 6+ messages in thread
From: Sape Mullender @ 2008-08-05 18:16 UTC (permalink / raw)
To: 9fans
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I wonder why there is a command to turn on DMA on disks. Could
it be that some disks don't work with DMA on?
Sape
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From: sqweek <sqweek@gmail.com>
To: "Fans of the OS Plan 9 from Bell Labs" <9fans@9fans.net>
Subject: [9fans] Bizarre freeze
Date: Wed, 6 Aug 2008 02:01:17 +0800
Message-ID: <140e7ec30808051101n5df6bcdbx4ab515e643f5d9f@mail.gmail.com>
Ran into an interesting one setting up my cpu server. The following
reliably freezes the box:
# echo dma on >/dev/sdC0/ctl
# 9fat:
Leaves the console totally unresponsive, no ^T^Tp, no ^P. rc -x on
9fat: gives "rfork e" as the final command.
sdC0 is a cdrom. I can turn dma on for my sata disks (sdE0/sdF0) no problem.
-sqweek
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] Bizarre freeze
2008-08-05 18:16 ` Sape Mullender
@ 2008-08-05 18:26 ` ron minnich
2008-08-05 19:01 ` erik quanstrom
2008-08-07 10:17 ` matt
0 siblings, 2 replies; 6+ messages in thread
From: ron minnich @ 2008-08-05 18:26 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
On Tue, Aug 5, 2008 at 11:16 AM, Sape Mullender
<sape@plan9.bell-labs.com> wrote:
> I wonder why there is a command to turn on DMA on disks. Could
> it be that some disks don't work with DMA on?
sure. it's PC hardware, so it's crap :-)
ron
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] Bizarre freeze
2008-08-05 18:26 ` ron minnich
@ 2008-08-05 19:01 ` erik quanstrom
2008-08-07 10:17 ` matt
1 sibling, 0 replies; 6+ messages in thread
From: erik quanstrom @ 2008-08-05 19:01 UTC (permalink / raw)
To: 9fans
>> I wonder why there is a command to turn on DMA on disks. Could
>> it be that some disks don't work with DMA on?
>
> sure. it's PC hardware, so it's crap :-)
> ron
the ata spec does not require dma for pata devices.
sata, first specified in ata 7, requires udma mode 5,
though sata:pata bridges routinely do not.
it's impossible to know without a bit more information,
but the dma command may be a red herring.
> sdC0 is a cdrom. I can turn dma on for my sata disks (sdE0/sdF0) no problem.
can you access the cdrom at all? i'm wondering if
you're accessing a ahci-capable chipset in ahci *and*
ata modes at the same time.
- erik
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] Bizarre freeze
2008-08-05 18:26 ` ron minnich
2008-08-05 19:01 ` erik quanstrom
@ 2008-08-07 10:17 ` matt
1 sibling, 0 replies; 6+ messages in thread
From: matt @ 2008-08-07 10:17 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
> Could it be that some disks don't work with DMA on?
Not all compact flash supports DMA
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] Bizarre freeze
@ 2008-08-05 19:49 erik quanstrom
0 siblings, 0 replies; 6+ messages in thread
From: erik quanstrom @ 2008-08-05 19:49 UTC (permalink / raw)
To: 9fans
> > I wonder why there is a command to turn on DMA on disks. Could
> > it be that some disks don't work with DMA on?
> sure. it's PC hardware, so it's crap :-)
unfortunately, this isn't a pc hardware thing. pata
devices are not required to support dma. ata 7, which
is the first to include sata support, requires udma mode
5 support. (many sata:pata bridges violate this part of
the spec, e.g. sata doms.)
but i'm wondering if dma support isn't a red herring.
> sdC0 is a cdrom. I can turn dma on for my sata disks (sdE0/sdF0) no problem.
it could be that this is a chipset that advertizes sata and
pata pci devices concurrently, but only one may be accessed
by the operating system. some ich 7 chipsets fall into this
category.
does this also hang your machine?
echo probe|scuzz
if so, i would put some debugging in atapktio.
otherwise, it just might be a bug in sdata.c
- erik
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2008-08-07 10:17 UTC | newest]
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2008-08-05 18:01 [9fans] Bizarre freeze sqweek
2008-08-05 18:16 ` Sape Mullender
2008-08-05 18:26 ` ron minnich
2008-08-05 19:01 ` erik quanstrom
2008-08-07 10:17 ` matt
2008-08-05 19:49 erik quanstrom
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