[stgt] [PATCH] Put locking around each entry in cmd_hash_list

[FUJITA Tomonori]

On Thu, 22 Sep 2011 16:33:50 -0700
Andy Grover <agrover at redhat.com> wrote:

> On 09/21/2011 11:53 PM, FUJITA Tomonori wrote:
> > On Wed, 21 Sep 2011 15:38:45 -0700
> > Andy Grover <agrover at redhat.com> wrote:
> > 
> >> Both the receiving thread and the bs worker threads access the hash of
> >> lists at it_nexus->cmd_hash_list. It may be the case that this is causing
> > 
> > Really? Can you explain how worker threads touch
> > it_nexus->cmd_hash_list?
> 
> Sorry, I was wrong, they don't.
> 
> But, the backtraces point strongly at list corruption when traversing a
> list off of the cmd_hash_list in abort_task_set(). Kiefer also mentioned
> reducing the number of worker threads seemed to help. But maybe that
> just lowered performance so the issue was less likely? I thought it
> might be interesting to see if a possible race was fixed by locking
> around that structure. Now that I have a better understanding of the tgt
> event loop mechanism, there don't appear to be any accesses to
> cmd_hash_list except by the main thread.
> 
> How else could this be happening? Use after free?

We might handle the same command twice. I don't have a clear idea yet.

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