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Date: Tue, 27 Apr 2010 11:07:49 +0100
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From: Martin Simmons <martin@lispworks.com>
To: freebsd-threads@freebsd.org
In-reply-to: <6AD0A971B01FA1DE632BAF65@HPQuadro64.dmpriest.net.uk> (message
	from Karl Pielorz on Tue, 27 Apr 2010 09:00:35 +0100)
References: <6AD0A971B01FA1DE632BAF65@HPQuadro64.dmpriest.net.uk>
Subject: Re: Advice / best practice - thread connection pools / mutexes
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Assuming it is safe share MySQL connections between threads like that (I don't
know), then using a data structure to track the unused connections sounds like
the simplest approach.

Protect access to the data structure with a mutex and use a condition variable
to wait (with pthread_cond_wait) for a free connection if they are all in use.

When a connection is freed, use pthread_cond_signal to wake a waiting thread.
Note that both pthread_cond_wait and pthread_cond_signal must be called while
holding the mutex to prevent missed wakups.

__Martin