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From: David Howells on 12 May 2010 06:50
Michel Lespinasse <walken(a)google.com> wrote:
> If there are no active threasd using a semaphore, it is always correct to
> unqueue blocked threads. This seems to be what was intended in the undo code.
> What was done instead, was to look for a sem count of zero - this is an
> impossible situation, given that at least one thread is known to be queued
> on the semaphore. The code might be correct as written, but it's hard to
> reason about and it's not what was intended (otherwise the goto out would
> have been unconditional).
> Go for checking the active count - the alternative is not worth the headache.
I think this is a definite bug fix, so I've sent it upstream in advance.
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