BUG: soft lockup detected on CPU#0!

I got this on a server box today. Kernel 2.6.21, x86_64, LVM2:

Jun 19 10:58:16 phoenix Ending XFS recovery on filesystem: dm-5 (logdev: internal)
Jun 19 10:58:16 phoenix BUG: soft lockup detected on CPU#0!
Jun 19 10:58:16 phoenix
Jun 19 10:58:16 phoenix Call Trace:
Jun 19 10:58:16 phoenix <IRQ>  [<ffffffff80277a60>] wake_up_process+0x10/0x20
Jun 19 10:58:16 phoenix [<ffffffff80297829>] softlockup_tick+0xe9/0x110
Jun 19 10:58:16 phoenix [<ffffffff8024dc93>] run_local_timers+0x13/0x20
Jun 19 10:58:16 phoenix [<ffffffff802815e7>] update_process_times+0x57/0x90
Jun 19 10:58:16 phoenix [<ffffffff8026eea4>] smp_local_timer_interrupt+0x34/0x60
Jun 19 10:58:16 phoenix [<ffffffff8026f49e>] smp_apic_timer_interrupt+0x4e/0x70
Jun 19 10:58:16 phoenix [<ffffffff8025ed56>] apic_timer_interrupt+0x66/0x70
Jun 19 10:58:16 phoenix <EOI>  [<ffffffff8026368c>] _spin_unlock_irqrestore+0xc/0x10
Jun 19 10:58:16 phoenix [<ffffffff80221acb>] __up_read+0x9b/0xb0
Jun 19 10:58:16 phoenix [<ffffffff8028d6e9>] up_read+0x9/0x10
Jun 19 10:58:16 phoenix [<ffffffff8034699d>] xfs_iunlock+0x3d/0xa0
Jun 19 10:58:16 phoenix [<ffffffff80362b1a>] xfs_rwunlock+0x3a/0x50
Jun 19 10:58:16 phoenix [<ffffffff80369c46>] xfs_vm_bmap+0x66/0x90
Jun 19 10:58:16 phoenix [<ffffffff8025cecc>] bmap+0x1c/0x20
Jun 19 10:58:16 phoenix [<ffffffff802a684e>] sys_swapon+0x6ae/0xae0
Jun 19 10:58:16 phoenix [<ffffffff8025e11e>] system_call+0x7e/0x83

What does it tell me?

Regards,
Hannes Dorbath

That you've got a fragemented swap file and that sys_swapon() does not yield the CPU in it's main loop that maps the extents in the swap file.

Harmless, AFAICT.

Cheers,

Dave.

Dave Chinner
Principal Engineer
SGI Australian Software Group