This is a classical synchronization problem with a classical solution:
You treat the readers as a group, and the writers individually. So you
have a write lock that each writer has to acquire and release, but it is
acquired only by the first reader and released by the last one.
Therefore you need a counter of the number of readers, and manipulations
of this counter must be protected by another lock.
I was going to suggest a similar approach but refused to because of a
problem I see with your code as well - if the readers are reading very
fast (the OP didn't state what his actual application is, so it might
not be a consumer-producer scheme which I don't think a dict would be
the natural choice anyway) they can block the writer from writing
alltogether.
Or do I miss something here?
Diez
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