Bug 509614 - Incomplete Panic Messages from Kdump VMCore
Incomplete Panic Messages from Kdump VMCore
Product: Red Hat Enterprise Linux 5
Classification: Red Hat
Component: kexec-tools (Show other bugs)
All Linux
medium Severity medium
: rc
: ---
Assigned To: Neil Horman
Red Hat Kernel QE team
Depends On:
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Reported: 2009-07-04 01:09 EDT by CAI Qian
Modified: 2009-09-06 23:09 EDT (History)
1 user (show)

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Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2009-08-06 19:44:48 EDT
Type: ---
Regression: ---
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RHEL 7.3 requirements from Atomic Host:
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Description CAI Qian 2009-07-04 01:09:55 EDT
Description of problem:
There looks like a problem which will block the following RHEL5.4 feature working properly,

Bug 475414 - FEAT RHEL5.4: [kdump] Salvaging panic messages from kdump vmcore

Bug 485308 - FEAT RHEL5.4: [kdump] Salvaging panic messages from kdump vmcore

I am getting incomplete dmesgs on almost all architectures with or without filtering VMCores (although I don't think whether filtering or not is really matter, "makedumpfile --dump-dmesg" is running on /proc/vmcore directly anyway, i.e., never on a filtered VMCore). Anyway, I have tested it for both with or without filtering, but the results are the same -- incomplete dmesgs.

# cat /etc/kdump.conf
ext3 /dev/mapper/VolGroup00-LogVol00
core_collector makedumpfile -c -d 31
kdump_post /bin/dump-dmesg-script

# cat /bin/dump-dmesg-script

makedumpfile --dump-dmesg /proc/vmcore /mnt/dmesg.txt

exit 0

After the kdump finished, I am getting the following files,

1) i386
# cat dmesg.txt
<5>Linux version 2.6.18-156.el5

2) ppc
# cat dmesg.txt
<6>Using pSeries machine description
<7>Page orders: linear map

3) x86_64
# cat dmesg.txt
<5>Linux version 2.6.18-156.el5

In addition, it also does not work without filtering,

# cat /etc/kdump.conf
ext3 /dev/mapper/VolGroup00-LogVol00
extra_bins /sbin/makedumpfile
kdump_post /bin/dump-dmesg-script

# cat /bin/dump-dmesg-script

makedumpfile --dump-dmesg /proc/vmcore /mnt/dmesg.txt

exit 0

1) i386
# cat dmesg.txt
<5>Linux version 2.6.18-156.el5

2) x86_64
# cat dmesg.txt
<5>Linux version 2.6.18-156.el5

3) ppc
# cat dmesg.txt
<6>Using pSeries machine description
<7>Page orders: linear map

4) ia64
# cat dmesg.txt
<5>Linux version 2.6.18-156.el5

For the data point, if I manually run this command when login into the kdump kernel, i.e., run through INIT process; disable kdump daemon, I can see that the dmesg file is more complete. Note, this should not be considered as a workaround of this problem, because kdump has seldom been used this way.

# makedumpfile --dump-dmesg /proc/vmcore dmesg.txt

makedumpfile Completed.

# cat dmesg.txt
<5>Linux version 2.6.18-156.el5PAE (mockbuild@ls20-bc1-14.build.redhat.com) (gcc
version 4.1.2 20080704 (Red Hat 4.1.2-44)) #1 SMP Mon Jun 29 18:34:12 EDT 2009
<6>BIOS-provided physical RAM map:
<4> BIOS-e820: 0000000000010000 - 000000000009b000 (usable)
<4> BIOS-e820: 000000000009b000 - 00000000000a0000 (reserved)
<4> BIOS-e820: 00000000000ce000 - 0000000000100000 (reserved)
<4> BIOS-e820: 0000000000100000 - 00000000e3f70000 (usable)
<4> BIOS-e820: 00000000e3f70000 - 00000000e3f77000 (ACPI data)
<4> BIOS-e820: 00000000e3f77000 - 00000000e3f80000 (ACPI NVS)
<4> BIOS-e820: 00000000e3f80000 - 00000000e4000000 (reserved)
<4> BIOS-e820: 00000000fec00000 - 00000000fec00400 (reserved)
<4> BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
<4> BIOS-e820: 00000000fff80000 - 0000000100000000 (reserved)
<4> BIOS-e820: 0000000100000000 - 0000000400000000 (usable)

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. configure kdump using the above kdump.conf and dump-dmesg-script.
2. manually crash the system -- SysRq-C.
3. cat /dmesg.txt (assume /dev/mapper/VolGroup00-LogVol00 is the root
Actual results:
incomplete demsg

Expected results:
complete desmg
Comment 1 Neil Horman 2009-07-04 14:10:13 EDT
I disagree with your assertion regarding the workaround.  Nothing in the origional RFE indicates that the feature needs to be used from within kdump itself. It just requests that we be able to extract the dmesg log from a vmcore without needing to have the debuginfo pacage installed (as crash would otherwise require).  To say that kdump is seldom used this way is a misnomer, since kdump has never been able to be used this way previously.  Certainly I need to look at this problem and fix it, but I don't see why it needs to block the 5.4 release (especially since I think it went out already).  Adjusting flags for 5.5

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