linux-kernel - Re: [PATCH v5] posix timers: allocate timer id per process

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Date:	Tue, 23 Oct 2012 23:47:33 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	Stanislav Kinsbursky <skinsbursky@...allels.com>,
	peterz@...radead.org, mingo@...hat.com, devel@...nvz.org,
	linux-kernel@...r.kernel.org, xemul@...allels.com
Subject: Re: [PATCH v5] posix timers: allocate timer id per process

On Tue, 23 Oct 2012, Eric Dumazet wrote:

> On Tue, 2012-10-23 at 11:40 +0400, Stanislav Kinsbursky wrote:
> > This patch is required CRIU project (www.criu.org).
> > To migrate processes with posix timers we have to make sure, that we can
> > restore posix timer with proper id.
> > Currently, this is not true, because timer ids are allocated globally.
> > So, this is precursor patch and it's purpose is make posix timer id to be
> > allocated per process.
> > 
> > Patch replaces global idr with global hash table for posix timers and
> > makes timer ids unique not globally, but per process. Next free timer id is
> > type of integer and stored on signal struct (posix_timer_id). If free timer id
> > reaches negative value on timer creation, it will be dropped to zero and
> > -EAGAIN will be returned to user.
> > 
> > Hash table has 512 slots.
> > Key is constructed as follows:
> > key = hash_32(hash_32(current->signal) ^ posix_timer_id));
> > 
> > Note: with this patch, id, returned to user, is not the minimal free
> > amymore. It means, that id, returned to user space in loop, listed below, will
> > be increasing on each iteration till INT_MAX and then dropped to zero:
> > 
> > while(1) {
> > 	id = timer_create(...);
> > 	timer_delete(id);
> > }
> > 
> > Signed-off-by: Stanislav Kinsbursky <skinsbursky@...allels.com>
> > 
> > ---
> 
> SGTM

Not so good to me.
 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

And that should be either an Acked-by or a Reviewed-by. You can't sign
off on patches which have not been submitted or transported by you.

Thanks,

	tglx


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