[Xen-devel] Dom0 hang caused by DomU crash

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

I have found that I can hang Dom0 for upwards of 5 minutes from DomU
when I use my GPL PV drivers. Can anyone tell me something about this
crash?:

"
BUG: soft lockup detected on CPU#0!

Call Trace:
 <IRQ> [<ffffffff8029fb2c>] softlockup_tick+0xdb/0xed
 [<ffffffff80267dba>] timer_interrupt+0x38d/0x3db
 [<ffffffff80211154>] handle_IRQ_event+0x2d/0x60
 [<ffffffff8029fe6b>] __do_IRQ+0xa4/0x105
 [<ffffffff8028364e>] _local_bh_enable+0x59/0xb3
 [<ffffffff802665a8>] do_IRQ+0x65/0x73
 [<ffffffff80360feb>] evtchn_do_upcall+0x86/0xe0
 [<ffffffff8025c616>] do_hypervisor_callback+0x1e/0x2c
 <EOI> [<ffffffff8020622a>] hypercall_page+0x22a/0x1000
 [<ffffffff8020622a>] hypercall_page+0x22a/0x1000
 [<ffffffff803607c4>] force_evtchn_callback+0xa/0xb
 [<ffffffff8036a7a3>] make_response+0xeb/0x131
 [<ffffffff8036b020>] blkif_schedule+0x24f/0x328
 [<ffffffff8028fa70>] autoremove_wake_function+0x0/0x2e
 [<ffffffff8028f8ad>] keventd_create_kthread+0x0/0x61
 [<ffffffff8036add1>] blkif_schedule+0x0/0x328
 [<ffffffff8028f8ad>] keventd_create_kthread+0x0/0x61
 [<ffffffff8023352b>] kthread+0xd4/0x107
 [<ffffffff8025c86c>] child_rip+0xa/0x12
 [<ffffffff8028f8ad>] keventd_create_kthread+0x0/0x61
 [<ffffffff80233457>] kthread+0x0/0x107
 [<ffffffff8025c862>] child_rip+0x0/0x12
"

This is happening when the windows DomU is performing a crash dump
(manually triggered). The windows crash dump environment for scsiport
drivers (which xenvbd is) is at a very high IRQL, eg with all interrupts
disabled. Apart from making it a real pain to code for, I think it might
have something to do with this crash...

After 5 or so minutes, Dom0 comes good again, and DomU gets a bit
further down the crash dump path before really crashing hard. The point
at which the Dom0 'BUG' occurs is before the final DomU crash though...

Can anyone tell me what sort of conditions could cause this to happen to
Dom0?

Thanks

James

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