Re: [Boost-users] [Thread] Writer/Reader strange scheduling

Subject: Re: [Boost-users] [Thread] Writer/Reader strange scheduling
From: Gaetano Mendola (mendola_at_[hidden])
Date: 2010-08-10 11:28:23

On 08/10/2010 05:05 PM, Roland Bock wrote:
> On 08/10/2010 04:28 PM, Stefan Strasser wrote:
>>> isn't that a waste? Why make reader 3 and 4 waiting and then make
>>> those running
>>> before the writer? The code to reproduce that is at the end.
>>
>> I don't think Boost.Thread specifies this behaviour, so it is probably
>> platform-dependent.
>> I'm guessing readers 3 and 4 have to wait because the writer thread
>> requested an exclusive lock (and otherwise the writer thread would be
>> starved), but once all locks have been released it is a decision of the
>> OS scheduler which thread is then woken up first and can acquire a lock
>> - one of the reader threads in this case apparently.
> 
> Right, if you want an "order preserving shared mutex", you have to write it yourself.

That was clear to me, still I think, I don't know who fault is, having a reader
waiting and then being scheduled is a waste :D

I guess I'll write one my self.

Regards
Gaetano Mendola