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

[Andy Grover]

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?

Regards -- Andy
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