Re: [PATCH RFC] big reader semaphore take#2

[Nick Piggin <nickpiggin@yahoo.com.au>]

Tejun Heo wrote:
> Nick Piggin wrote:

>> The upshot of that would be that you could build the whole thing
>> from rwsem infrastructure and have basically zero other locking
>> mechanisms or complexity that you don't want in a synchronisation
>> primitive.
>>
> 
> To certain extent, I do agree with you - it's safer/simpler..., but on 
> the other hand, new brsem isn't that more complex and would perform 
> almost identically without extra semantical baggage.  So, I thought it 
> might be worth a bit more effort.
> 

I would do it thisway if possible, yes.

> Hmm... So, array of rwsem's, it should be.
> 

First implementation would be per-cpu just rwsems. A second patch
to make it just an array rwsem->count's plus a shared queue may
be in order - OTOH everyone does their own rwsems, so this will be
a bit of a headache.

I forget - are you just planning to use one global brsem? In this
case the size issue wouldn't be a pressing one.

-- 
SUSE Labs, Novell Inc.

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