Re: Mixing pass-through I/o with standard block I/O?

Douglas Gilbert (dgilbert@interlog.com)
Fri, 17 Sep 1999 23:33:32 -0400

"casler, heather" wrote:
>
> Hello....is there a restriction on mixing pass-through I/O and standard
> block I/O?
> I'm using an inquiry command that goes out to identify and list the
> /dev/sg"x" devices which is hanging the machine I'm using. It's a Dell
> PowerEdge 2300 running 2.2.11 w/ tcp.diff patch, 2 450MHz cpu's , 512MB,
> 4.3GB Seagate, and attached to an external differential storage device
> (Symmetrix) via AHA-2944UW. It appears to be entirely hanging the system
> when the inquiry command hits /dev/sga (internal root drive)....no oops or
> core dump and no hot keys are available.

Heather,
There is no restriction. I do it all the time when testing.
My root file system is on a SCSI disk corresponding to
/dev/sgb and as I write this email the following is executing:
# sg_dd512 if=/dev/sgb of=/dev/null
That command is a variant of "dd" that uses the sg
device (with 512 byte blocks in this case). My hardware is
different: AMD K6-2 300MHz, Advansys 940UW, IBM DCHS04U
disk using kernel 2.2.12 .

Note that I never try to write to that disk through the
sg device! That obviously wouldn't be very clever. The SCSI
INQUIRY command should be perfectly safe in all contexts.
So it seems like a SMP related problem.

Doug Gilbert

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