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From: Alexander Monakov <amonakov@ispras.ru>
Newsgroups: gmane.linux.lib.musl.general
Subject: Re: semaphore redesign
Date: Sun, 1 Mar 2015 21:54:13 +0300 (MSK)
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A few more things from IRC discussion.

Fields in the semaphore struct should be made volatile.

The new implementation eliminates the last call site with non-dummy cleanup
argument to __timedwait.

New sem_timedwait shows worse performance in Rich's sem-bench on my desktop, I
think primarily because it does not have sem_trywait preceding the spin loop
anymore, plus the loop itself is also a bit leaner.  My proposal is to use a 
different spin count somewhere in 150-200 range instead of 100.

Alexander