My server (SUSE ppc) became un-responsive, no one can login, but it pings, I am NOT able to open a terminal window even from the HMC console, it has to be rebooted through HMC. Then its fine again.

/var/log/messages show this

21:54:35 myserver kernel: kernel BUG in shmem_writepage at mm/shmem.c:864!
21:54:35 myserver kernel: Oops: Exception in kernel mode, sig: 5 [#1]
21:54:35 myserver kernel: SMP NR_CPUS=128 NUMA PSERIES LPAR
21:54:35 myserver kernel: Modules linked in: joydev st ide_cd lp parport_pc parport mmfs mmfslinux tracedev ipv6 autofs4 nfsd exportfs
nfs lockd nfs_acl sunrpc apparmor aamatch_pcre loop sr_mod cdrom s2io pata_pdc2027x e1000 linear raid1 raid0 dm_snapshot dm_mod raid5 xor sg i
pr libata firmware_class sd_mod scsi_mod
21:54:35 myserver kernel: NIP: C0000000000C479C LR: C0000000000C4790 CTR: C0000000000C46C8
21:54:35 myserver kernel: REGS: c00000000fb57800 TRAP: 0700 Tainted: P U (2.6.16.37-0.17-ppc64)
21:54:35 myserver kernel: MSR: 8000000000029032 <EE,ME,IR,DR> CR: 24000042 XER: 00000018
21:54:35 myserver kernel: TASK = c00000000f81e9d0[584] 'kswapd0' THREAD: c00000000fb54000 CPU: 2
21:54:35 myserver kernel: NIP [C0000000000C479C] .shmem_writepage+0xd4/0x1cc
21:54:35 myserver kernel: LR [C0000000000C4790] .shmem_writepage+0xc8/0x1cc
.
.
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21:54:35 myserver kernel: LR [C0000000000C4790] .shmem_writepage+0xc8/0x1cc
.
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At this point of time the server went unresposive!!!

Some info about my environment:
SUSE Linux Enterprise Server 10 SP1 Beta3 (ppc)
kernel-ppc64-2.6.16.37-0.17

Can this be diagonosed and prevented in future ?
Thanks

Do you really have 128 CPUs? If not, it looks like you have a problem here.

You might try not using a Beta kernel. Rolling back to an earlier version may make the problem go away.