ZFS freeze/livelock
Willem Jan Withagen
wjw at digiware.nl
Wed Oct 13 16:16:15 UTC 2010
On 2010-10-13 13:08, Borja Marcos wrote:
>
> On Oct 10, 2010, at 5:34 PM, Willem Jan Withagen wrote:
>
>> Hi,
>>
>> Just had my FreeBSD freeze on me with what I would think is sort of
>> an livelock....
>>
>> While I was receiving zfs snapshots on my data pool.
> There is an (as far as I know) unsolved deadlock situation when
> receiving a snapshot while you read the target dataset.
>
> I found it in a redundant server configuration. I replicate some
> datasets periodically doing an incremental send-receive. It works
> perfectly but it can deadlock if I have a process reading the
> destination dataset on the secondary server. And those things can
> happen if you have, for example, one of the nightly periodic tasks
> running.
>
> Were you doing a siimilar thing? Or are you sure there was no reading
> activity on the destination dataset?
Well I think what I did more or less fits your desciption.
But thusfar it did not happen.
And I'm (very slowly) redoing some of these steps, with all debugging
settings in the kernel.
# Debugging for use in -current
options KDB # Enable kernel debugger support.
options DDB # Support DDB.
options GDB # Support remote GDB.
options INVARIANTS # Enable calls of extra sanity
checking
options INVARIANT_SUPPORT # Extra sanity checks of
internal structures, required by INVARIANTS
options WITNESS # Enable checks to detect
deadlocks and cycles
options WITNESS_SKIPSPIN # Don't run witness on spinlocks
for speed
Things are real sloooooooooow now.
--WjW
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