Re: [boost] [Interprocess::Semaphore] Deadlock on more producers - one consumer problem

Subject: Re: [boost] [Interprocess::Semaphore] Deadlock on more producers - one consumer problem
From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2009-06-19 17:04:59

James Mansion wrote:

> The post operation that 'wakes up' is V, not P.

Ooops, yes, I meant V.

> If your api allows V(4) to release 4 resources atomically, then 4 
> consumers in P must be released (if they are
> waiting, and any left over accrued to allow future consumers not to 
> block.  Even if you say V(4) is not supported
> and actually V;V;V;V and these are atomic individually, then there is 
> still a race between those four posts
> and any Ps actually getting to run.  Either way, you MUST enable 4-off 
> Ps to become ready.  If the API allows to
> post multiple resources atomically, then you need to handle this.

No, the API just allows V(1). And VxN operations is what I'm suggesting 
if N resources are freed by the producer. Is it usual to have V(N) in 
semaphores? I have never seen it.

Best,

Ion