linux-kernel - Re: sched_yield() on 2.6.25

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Date:	Mon, 09 Jun 2008 11:03:55 +0200
From:	Helge Hafting <helge.hafting@...el.hist.no>
To:	Jakub Jozwicki <jozwicki@...er.pl>
CC:	linux-kernel@...r.kernel.org, Robert Hancock <hancockr@...w.ca>
Subject: Re: sched_yield() on 2.6.25

Jakub Jozwicki wrote:
> From the man sched_yield:
>
> A  process  can  relinquish  the  processor  voluntarily without blocking by
> calling sched_yield().  The process will then be moved to the  end  of  the 
> queue  for  its static priority and a new process gets to run.
>
> and also IEEE/Open Group:
> http://www.opengroup.org/onlinepubs/000095399/functions/sched_yield.html
>
>   
>>> 	pthread_mutex_lock(&mutex);
>>> 	th = pthread_self();
>>> 	if (pthread_equal(th,last_th)) {
>>> 	    pthread_mutex_unlock(&mutex);
>>> 	    sched_yield();
>>> 	    continue;
>>>       
>
> Here with SCHED_OTHER sched_yield for the first 100-200 times does nothing.
> Should the man be updated?
>   
Having the man page mention the fact that that sched_yield() probably
won't do "what  you intend"  in the non-realtime cases is probably a 
good idea;
that way we get fewer application programmers who mistakenly think
that sched_yield can be used for their purposes. And then we'll have
less broken apps. 

A pointer to info about what they might want to use instead is even better.

Helge Hafting

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