On 18/05/2013 00:37, Roland Dreier wrote:
you see that when freeing a CQ, we first do the HW2SW_CQ firmware
command; once this command completes, no more events will be generated
for that CQ. Then we do synchronize_irq for the CQ's interrupt
vector. Once that completes, no more completion handlers will be
running for the CQ, so we can safely delete the CQ from the radix tree
(relying on the radix tree's safety of deleting one entry while
possibly looking up other entries, so no lock is needed). We also use
the lock to synchronize against the CQ event function, which as you
noted does take the lock too.
Basic idea is that we're tricky and careful so we can make the fast
path (completion interrupt handling) lock-free, but then use locks and
whatever else needed in the slow path (CQ async event handling, CQ
destroy).
Jack, so do we finally agree to this analysis? last time when this was
on the list, I was under the impression that there was no consensus and
I also see that on the stack we provide to customers there's a patch of
yours in that area, or it may fix another bug?
Or.
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