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SubjectRe: [PATCH] block: strip out locking optimization in put_io_context()
From
2012/2/14 Tejun Heo <tj@kernel.org>:
> Hello, Shaohua.
>
> Can you please test the following patch?  It's combination of three
> patches which invokes elevator icq exit from exit_io_context().  This
> unfortunately ends up adding another reverse locking loop and using
> RCU could be better; unfortunately, the change isn't trivial due to
> q->queue_lock modification during blk_cleanup_queue() and ioc cleanup
> being called after that from blk_release_queue() - IOW, while holding
> RCU, we might end up grabbing the wrong q lock (I don't think this is
> a new problem).
>
> Now that we have proper request draining on queue exit, we can
> probably move ioc clearing and other operations to blk_cleanup_queue()
> and then apply RCU, but that's for another merge window.
This fixed the regression. Thanks!
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