> On Nov 5, 2015, at 6:56 PM, Chris Leech <cle...@redhat.com> wrote:
>
> On Thu, Nov 05, 2015 at 02:33:44PM -0200, Guilherme G. Piccoli wrote:
>> Hello Shlomo and Or,
>>
>> I'm Guilherme Piccoli from LTC/IBM - firstly, sorry to bother you.
>>
>>
>> We are running some tests with iSCSI and we found an issue caused possibly
>> by commit 659743b02c41 ("libiscsi: Reduce locking contention in fast path").
>>
>> After some time (+/- 1 hour) of testing with a hardware target (using fio
>> benchmark tool), we got a kernel oops; the following link is a pastebin of
>> the error message (we got lots of these messages, since our system has
>> multiple cores): http://codepad.org/KS2C9Jjt
>
> Interesting. From the trace, the list debugging code is detecting
> corruption when removing a task from some list. Could be the connection
> mgmtqueue, cmdqueue, or requeue.
>
> After the locking change adding a task to any of those lists is under
> the session fwrd_lock, but the call to iscsi_complete_task which deletes
> the task from whatever list it's on is under the back_lock.
>
> Am I missing something, or is splitting a linked list across two locks a
> major failing of this change?
You are right. Patch is really wrong. Not sure what I was thinking when I
merged it. It has had multiple issues now,
Or and Shlomo, I am going to just revert the patch for now until I can do some
performance testing with a patch to add back correct locking and also
re-rerview the patch. Maybe instead of locks I can just use some kfifos too.
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