[6689] in linux-scsi channel archive
Re: hot key sequence/ kernel NULL pointer help??
daemon@ATHENA.MIT.EDU (Gilbert, Douglas)
Wed Jun 16 15:25:36 1999
From: "Gilbert, Douglas" <douglas.gilbert@rbcds.com>
To: "'heather=casler%eng%emchop1@fishbowl02.lss.emc.com'" <heather=casler%eng%emchop1@fishbowl02.lss.emc.com>
Cc: "'linux-scsi@vger.rutgers.edu'" <linux-scsi@vger.rutgers.edu>
Date: Wed, 16 Jun 1999 14:28:47 -0400
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Heather wrote:
> Is there any type of hot key sequence that can be used to create a system
> dump even after the system has frozen?
In the "kernel hacking" section of the kernel configure select
"Magic SysRq key" before rebuilding you kernel.
Then after a SCSI sub-system meltdown try:
Alt-SysRq S [emergency sync]
Alt-SysRq U [remount read-only]
Alt-SysRq S [emergency sync]
[see linux/Documentation/sysrq.txt for other options]
......
Alt-SysRq B [reboot system!]
> I'm running 2.2.5 on a Compaq AP200 with an AHA-2940UW (for the boot
drive)
> and a QLA2100F for connectivity to an external storage device. I have the
> Qlogic card as a module and insmod'd it. When I do a dd (like #dd
> if=/dev/sdb of=/dev/null bs=16384 count=500) or try to send I/O to the
> external storage via an app called Iorate, I get the message below and the
> system freezes.
> I can't figure out what the fault address is referring to either. I did a
> #ksyms -m | sort and there's nothing that refers to the fault address of
> 00000000.
> Any suggestions are greatly appreciated. Thanks!
Build the Qlogic driver into the kernel (don't use it as
a module].
The SCSI mid-level always tries to allocate memory
below the 16 MB level irrespective of whether you
have any ISA adpaters (for backward compatibility
with the distant past). The oops is probably caused
because it cannot find that memory below 16MB returning
a NULL pointer causing ...
The Qlogic module may look like it loads ok but may
have 0 command blocks allocated causing an oops as
soon as you try and use it.
BTW It makes _no_ difference if your machine has 256MB
of RAM (it just makes it worse)!!
If the driver is built into the kernel then it tries
to get that memory at boot time when it is a lot more
likely to get find it.
Contact me if you need more help.
Doug Gilbert
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<P><FONT SIZE=2> Heather wrote:</FONT>
</P>
<P><FONT SIZE=2>> Is there any type of hot key sequence that can be used to create a system </FONT>
<BR><FONT SIZE=2>> dump even after the system has frozen?</FONT>
</P>
<P><FONT SIZE=2>In the "kernel hacking" section of the kernel configure select</FONT>
<BR><FONT SIZE=2>"Magic SysRq key" before rebuilding you kernel.</FONT>
</P>
<P><FONT SIZE=2>Then after a SCSI sub-system meltdown try:</FONT>
<BR><FONT SIZE=2>Alt-SysRq S [emergency sync]</FONT>
<BR><FONT SIZE=2>Alt-SysRq U [remount read-only] </FONT>
<BR><FONT SIZE=2>Alt-SysRq S [emergency sync]</FONT>
<BR><FONT SIZE=2>[see linux/Documentation/sysrq.txt for other options]</FONT>
<BR><FONT SIZE=2>......</FONT>
<BR><FONT SIZE=2>Alt-SysRq B [reboot system!]</FONT>
</P>
<P><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2>> I'm running 2.2.5 on a Compaq AP200 with an AHA-2940UW (for the boot drive) </FONT>
<BR><FONT SIZE=2>> and a QLA2100F for connectivity to an external storage device. I have the </FONT>
<BR><FONT SIZE=2>> Qlogic card as a module and insmod'd it. When I do a dd (like #dd </FONT>
<BR><FONT SIZE=2>> if=/dev/sdb of=/dev/null bs=16384 count=500) or try to send I/O to the </FONT>
<BR><FONT SIZE=2>> external storage via an app called Iorate, I get the message below and the </FONT>
<BR><FONT SIZE=2>> system freezes.</FONT>
<BR><FONT SIZE=2>> I can't figure out what the fault address is referring to either. I did a </FONT>
<BR><FONT SIZE=2>> #ksyms -m | sort and there's nothing that refers to the fault address of </FONT>
<BR><FONT SIZE=2>> 00000000.</FONT>
<BR><FONT SIZE=2>> Any suggestions are greatly appreciated. Thanks!</FONT>
</P>
<P><FONT SIZE=2>Build the Qlogic driver into the kernel (don't use it as </FONT>
<BR><FONT SIZE=2>a module].</FONT>
<BR><FONT SIZE=2>The SCSI mid-level always tries to allocate memory </FONT>
<BR><FONT SIZE=2>below the 16 MB level irrespective of whether you </FONT>
<BR><FONT SIZE=2>have any ISA adpaters (for backward compatibility </FONT>
<BR><FONT SIZE=2>with the distant past). The oops is probably caused </FONT>
<BR><FONT SIZE=2>because it cannot find that memory below 16MB returning </FONT>
<BR><FONT SIZE=2>a NULL pointer causing ...</FONT>
<BR><FONT SIZE=2>The Qlogic module may look like it loads ok but may</FONT>
<BR><FONT SIZE=2>have 0 command blocks allocated causing an oops as</FONT>
<BR><FONT SIZE=2>soon as you try and use it.</FONT>
<BR><FONT SIZE=2>BTW It makes _no_ difference if your machine has 256MB</FONT>
<BR><FONT SIZE=2>of RAM (it just makes it worse)!!</FONT>
</P>
<P><FONT SIZE=2>If the driver is built into the kernel then it tries </FONT>
<BR><FONT SIZE=2>to get that memory at boot time when it is a lot more </FONT>
<BR><FONT SIZE=2>likely to get find it.</FONT>
</P>
<P><FONT SIZE=2>Contact me if you need more help.</FONT>
</P>
<P><FONT SIZE=2>Doug Gilbert</FONT>
</P>
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