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Cc: Howard Chu <hyc@symas.com>, Christopher Friesen <cfriesen@nortel.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       hancockr@shaw.ca
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From: Kyle Moffett <mrmacman_g4@mac.com>
Subject: Re: pthread_mutex_unlock (was Re: sched_yield() makes OpenLDAP slow)
Date: Thu, 26 Jan 2006 09:15:15 -0500
To: Nick Piggin <nickpiggin@yahoo.com.au>
Sender: linux-kernel-owner@vger.kernel.org
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Haven't you OpenLDAP guys realized that the pthread model you're  
actually looking for is this?  POSIX mutexes are not designed to  
mandate scheduling requirements *precisely* because this achieves  
your scheduling goals by explicitly stating what they are.

s: pthread_mutex_lock(&mutex);
s: pthread_cond_wait(&wake_slave, &mutex);

m: [do some work]
m: pthread_cond_signal(&wake_slave);
m: pthread_cond_wait(&wake_master, &mutex);

s: [return from pthread_cond_wait]
s: [do some work]
s: pthread_cond_signal(&wake_master);
s: pthread_cond_wait(&wake_slave, &mutex);

Of course, if that's the model you're looking for, you could always  
do this instead:

void master_func() {
	while (1) {
		[do some work]
		slave_func();
	}
}

void slave_func() {
	[do some work]
}

The semantics are effectively the same.

Cheers,
Kyle Moffett

--
Premature optimization is the root of all evil in programming
   -- C.A.R. Hoare


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