linux-kernel - Re: [PATCH 1/3] posix timers: Allocate timer id per process (v2)

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Date:	Fri, 8 Mar 2013 13:50:28 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Pavel Emelyanov <xemul@...allels.com>
cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Matthew Helsley <matt.helsley@...il.com>,
	linux-api@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] posix timers: Allocate timer id per process (v2)

Pavel,

On Thu, 21 Feb 2013, Pavel Emelyanov wrote:

> 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);
> }
> 
> In this version the helpers from include/linux/hashtable.h are used
> instead of hand-made hash-table.

I think the patches are ready to go, though the changelog needs quite
some care.

It's explaining what the patch does and not why. Can you please
rework?

Thanks,

	tglx
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