I've now tested for this bug using a simplified methodology on the
latest patched-versions of the host (2.4.27 and 2.6.8) and guest
(2.4.27 and 2.6.9).
New methodology
My Debian guest system raises two xterms at startup. On each I log in
as root. On one, I enter:
while true; do echo >/dev/null; done
On the second, I enter:
cat /dev/urandom
The devastating symptom: within 5 seconds the guest kernel has paniced
and exited with the message (below) "kernel BUG at sched.c:564!".
Findings
guest 2.6.9: patched with uml-2.6.9-bb2.patch.bz2 - I am pleased to say
I have not so far been able to reproduce this bug on this configuration.
guest 2.4.27: patched with uml-2.4.27-bs1.patch and
uml-patch-2.4.24-1base.patch - no change; this bug is readily
reproducible and so IS NOT FIXED, regardless of whether the guest is
run on host 2.4.27 or 2.6.8
Conclusion
If such a simple pair of commands as this causes such devastating
consequences, it seems the 2.4.27 kernel sched.c line 564 needs to be
taken a look at - unless, that is, Jeff Dike's recent post about
uml-patch-2.4.27-1 "a nasty scheduler race fixed" addresses this bug.
Jeff: where can I get your uml-patch-2.4.27-1 ?
Struan
Struan Bartlett wrote:
Posted
to SourceForge:
For the record, this is not entirely fixed. I'm running a Debian host
with 2.4.25 kernel and host-skas3-2.4.25.patch, and a Debian
guest with 2.4.27 kernel and uml-patch-2.4.26-3.
In one xterm I ran "while true; do ls -la /dev/*; done" (see
also bug report 617709). In the other, "cat /dev/urandom".
After 5-10 seconds, the 'linux' host process crashes
completely with:
Scheduling in interrupt
Kernel panic: kernel BUG at sched.c:564!
In interrupt handler - not syncing
<6>SysRq : Show Regs
EIP: 0023:[<400e4b38>] CPU: 0 Not tainted ESP: 002b:bffffc68
EFLAGS: 00000246
Not tainted
EAX: ffffffda EBX: 00000001 ECX: 0804cdf0 EDX: 00001000
ESI: 00001000 EDI: 0804cdf0 EBP: bffffc88 DS: 002b ES: 002b
Call Trace: [<a0010e5f>] [<a00cae60>] [<a018db51>]
[<a018dade>] [<a000dc93>] [<a00cade9>]
[<a00b526f>] [<a0010e5f>] [<a001d2ec>]
[<a012d637>] [<a017561e>] [<a0010e5f>]
[<a017561e>] [<a0010405>] [<a00103f1>]
[<a0010e5f>] [<a000d965>] [<a017561e>]
[<a0175616>] [<a00b26ec>] [<a00bd0d1>]
[<a0015e2f>] [<a00bd268>] [<a00e1fc4>]
[<a00b4caf>] [<a00e0057>] [<a00c32d5>]
[<a00b4caf>] [<a00c3a6a>] [<a012f024>]
[<a00c42e2>] [<a00b2816>] [<a00b2855>]
[<a00b277e>] [<a00c3035>] [<a00c8bc0>]
[<a001622f>] [<a001a8e3>] [<a0016153>]
[<a001607b>] [<a0016037>] [<a00b26ec>]
[<a0015de1>] [<a0015dcf>] [<a00ada41>]
[<a00ada52>] [<a00b3dfe>] [<a00b4108>]
[<a00bb278>] [<a00bb211>] [<a00bb211>]
[<a00bb278>] [<a00b4bed>] [<a00b4ba8>]
[<a012ef38>] [<a014639d>] [<a014639d>]
[<a012ef38>] [<a00c8db0>] [<a00bb56e>]
[<a00bb3e0>] [<a00bb7f0>] [<a00b0404>]
[<a00bb7f0>] [<a00bb304>] [<a0053f2f>]
[<a00bb64c>] [<a00ab920>] [<a00b0404>]
[<a00bb3d4>] [<a00c8c7b>] [<a00bb304>]
[<a00bb458>] [<a00bb59c>] [<a00bb64c>]
[<a012f024>] [<a00bb59c>] [<a00bb3d4>]
[<a00b0404>] [<a00bb64c>] [<a00bb458>]
[<a00bb59c>] [<a00bb59c>] [<a00b597f>]
[<a00b2855>] [<a00bb458>] [<a00be776>]
[<a00be776>] [<a00be81d>] [<a0146380>]
[<a00b0658>] [<a00be81d>] [<a00e031b>]
[<a00e05d6>] [<a00bb59c>] [<a00e1458>]
[<a00bb637>] [<a00e0057>] [<a00e0057>]
[<a00c3a29>] [<a00c32d5>] [<a00c5f3d>]
[<a00c5e11>] [<a00c0e91>] [<a00c5d50>]
[<a0033e1a>] [<a00bad8e>] [<a00b35bb>]
[<a00b36e3>] [<a00baddc>] [<a00badd3>]
[<a00b9fb5>] [<a00ba0bd>] [<a00b01ba>]
[<a00ba31a>] [<a00b26ec>] [<a00baa87>]
[<a00baa71>] [<a012ef38>] [<a012efd1>]
-------------------------------------------------------
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