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Passing an admitted permit -- i.e. one with count resources on it -- to the multishard reader, will possibly result in a deadlock, because the permit of the multishard reader is destroyed after the permits of its child readers. Therefore its semaphore resources won't be automatically released until children acquire their own resources. This creates a dependency (an edge in the "resource allocation graph"), where the semaphore used by the multishard reader depends on the semaphores used by children. When such dependencies create a cycle, and permits are acquired by different reads in just the right order, a deadlock will happen. Users of the multishard reader have to be aware of this gotcha -- and of course they aren't. This is small wonder, considering that not even the documentation on the multishard reader mentions this problem. To work around this, the user has to call `reader_permit::release_base_resources()` on the permit, before passing it to the multishard reader. On multiple occasions, developers (including the very author of the multishard reader), forgot or didn't know about this and this resulted in deadlocks down the line. This is a design-flaw of the multishard reader, which is addressed in this patch, after which, it is safe to pass admitted or not admitted permits to the multishard reader, it will handle the call to `release_base_resources()` if needed.