Re: kgdb 2.3 hangs

On Tue, 2006-01-31 at 19:01 +0530, Amit Kale wrote:
> KGDB paniced right here ->
> 
> Sending packet: $mc0566328,4#9e...Packet instead of Ack, ignoring it
> 
> Any packets after this are unreliable.
> Looks like access to memory location 0xc0566328 caused the kernel to panic. 
> This address should be in direct mapped region of the kernel. It couldn't 
> have segfaulted here, besides we have tested kgdb 2.3 with different memory 
> accesses, to ensure that it doesn't panic this way.
> 
> Seems like the other processor tried to send some printk related packets (O 
> packets). Could you confirm whether all processors are in debugger? Issue "p 
> procindebug" It'll print the procindebug array. You should see as many 1s as 
> the number processors. If there are fewer 1s there, other processors are 
> still not inside KGDB, in which case you'll see behavior of this kind.

added this and this time hangs in another place i feel. log is attached.

ming



> 
> Is this an Opteron system? We have seen too many nmi problems on Opterons.
> -Amit
> 
> On Monday 30 Jan 2006 10:28 pm, Ming Zhang wrote:
> > On Mon, 2006-01-30 at 12:26 +0530, Amit Kale wrote:
> > > Tom, Ming,
> > >
> > > module debugging patch uses read memory packets, so it won't have any smp
> > > issues.
> > >
> > > Have you passed "nmi_watchdog=1" to kernel through grub.conf file? Please
> > > also check the output of dmesg, to confirm that NMI watchdog in deed
> > > works. If it doesn't you'll see a message in dmesg output. If
> > > nmi_watchdog=1 doesn't work try nmi_watchdog=2. (Yeah, seems like a joke,
> > > but that's exactly what it is :-)
> >
> > yes, i knew this nmi trick, it is funny.
> >
> > > I see two different issues here.
> > >
> > > 1. You could go ahead after turning off console messages over kgdb. This
> > > should be required. I would like to see a dump of packets with this
> > > option turned on. We'll get some idea about why this option is causing a
> > > problem.
> >
> > i selected it, compiled, and loaded the new kernel. got this.
> >
> > ----------------------------
> > This GDB was configured as "i686-pc-linux-gnu"...
> > (gdb) set remotebaud 57600
> > (gdb) set debug remote 1
> > (gdb) set solib-search-path /root/kgdb/module26
> > (gdb) target remote /dev/ttyS0
> > Remote debugging using /dev/ttyS0
> > Sending packet: $Hc-1#09...Ack
> > Packet received: OK
> > Sending packet: $qC#b4...Ack
> > Packet received: QC0000000000008000
> > Sending packet: $qOffsets#4b...Ack
> > Packet received:
> > Sending packet: $?#3f...Ack
> > Packet received: S05
> > Sending packet: $Hg8000#77...Ack
> > Packet received: OK
> > Sending packet: $g#67...Ack
> > Packet received:
> > 01000000c01a64c000000000728362c0209f60c0249f60c07b8362c042f762c
> > 08bbf14c08600000060000000680000007b0000007b000000ffff0000ffff0000
> > breakpoint () at kernel/kgdb.c:1776
> > 1776            atomic_set(&kgdb_setting_breakpoint, 0);
> > Sending packet: $mc0566328,4#9e...Packet instead of Ack, ignoring it
> > Packet instead of Ack, ignoring it
> > Packet instead of Ack, ignoring it
> > Packet instead of Ack, ignoring it
> > Packet instead of Ack, ignoring it
> > Bad checksum, sentsum=0xd1, csum=0x9b, buf=28356c0
> > Packet instead of Ack, ignoring it
> > Packet instead of Ack, ignoring it
> > Bad checksum, sentsum=0xd1, csum=0x9b, buf=28356c0
> > Packet instead of Ack, ignoring it
> > Packet instead of Ack, ignoring it
> > Bad checksum, sentsum=0xd1, csum=0x9b, buf=28356c0
> > Packet instead of Ack, ignoring it
> > Packet instead of Ack, ignoring it
> > Bad checksum, sentsum=0xd1, csum=0x9b, buf=28356c0
> > Packet instead of Ack, ignoring it
> > putpkt: Junk: 286356c0#d1
> > ----------------------------
> >
> > then after a while, saw this. seems that serial link is broken
> >
> >
> > Sending packet: $mc0566328,4#9e...putpkt: write failed: Input/output
> > error.
> >
> > (gdb) c
> > Continuing.
> > Sending packet: $Z0,c014bc80,1#38...putpkt: write failed: Input/output
> > error.
> > (gdb) c
> > Continuing.
> > Sending packet: $Z0,c014bc80,1#38...putpkt: write failed: Input/output
> > error.
> >
> > > I have seen a bug report earlier where console message packets got mixed
> > > up with regular gdb packets, don't know how. Couldn't reproduce it later.
> > > I think we should print a message from kgdb indicating that smp isn't
> > > working. Perhaps halt kernel at that point.
> > >
> > > 2. The output you have sent is rather limited. Could you send the _whole_
> > > output. That is right from the point where gdb prints it's initial
> > > version no. etc. to the point where debugging fails.
> > >
> > > -Amit
> > >
> > > On Friday 27 Jan 2006 9:12 pm, Ming Zhang wrote:
> > > > On Fri, 2006-01-27 at 08:31 -0700, Tom Rini wrote:
> > > > > On Fri, Jan 27, 2006 at 10:12:46AM -0500, Ming Zhang wrote:
> > > > > > thanks for the hint.
> > > > > >
> > > > > > now i deselect the "console message over kgdb" and use this 'set
> > > > > > debug remote 1', the boot process is good.
> > > > > >
> > > > > >
> > > > > > now is another problem.
> > > > > >
> > > > > > it hangs when loading module.
> > > > >
> > > > > You need to have a custom compiled GDB with the patches found in CVS,
> > > > > if you've also got the 'module.patch' patch applied.
> > > >
> > > > i run the gdb_mod 2.3 from download page. i assumed that is the one you
> > > > mentioned.
> > > >
> > > > > But I'll admit I haven't tested module autoloading stuff on SMP, but
> > > > > it should work.
> > > >
> > > > though i am using a dual opteron, i already disabled SMP and choose P4
> > > > for a 32bit compilation.
> > > >
> > > > ming
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
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