Re: [PATCH 0/2] eventfd: new EFD_STATE flag

From: Paolo Bonzini
Date: Tue Aug 25 2009 - 02:59:46 EST

There are userspace libraries that do almost everything, but you hardly
see things like pthread_(EFD_STATE-like)_create() or similar system
interfaces based on such abstraction.

It actually seems as close to a condition variable as an eventfd can be.

A pthread condition typical code usage maps to eventfd like:

while (read(efd, ...)> 0)

So a pthread condition is really a wakeup gate like eventfd is.
EFD_STATE has nothing to do with a pthread condition.

No, your code does not work for pthread_cond_broadcast (which arguably is the common case) because all the eventfd readers after the first would block.

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