Messages in this thread | | | Date | Thu, 2 Aug 2018 10:59:38 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH 2/4] aio: add a iocb refcount |
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On Thu, Aug 02, 2018 at 12:19:56AM +0100, Al Viro wrote: > On Mon, Jul 30, 2018 at 09:15:42AM +0200, Christoph Hellwig wrote: > > This is needed to prevent races caused by the way the ->poll API works. > > To avoid introducing overhead for other users of the iocbs we initialize > > it to zero and only do refcount operations if it is non-zero in the > > completion path. > > refcount_t looks like a bad match - you, AFAICS, have count 0 for everything > except poll, while for poll you start with 2. That looks like > if (iocb->shared && test_and_clear_bit(0, &iocb->shared)) > return; > kill the sucker > in your iocb_put() and initializing it to 1 in poll. No?
For non-poll we don't need the recount, so we can ignore that.
For poll we have two reference - submitting and wakee context. We could replace the refcount_t with an atomic bitops - but it would
a) make the code harder to read than plain old refcounting b) make the iocb bigger - at least for now as there is nothing else we can share that unsigned long with.
Your call - I can respin it either way.
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