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

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Date:	Thu, 14 Feb 2013 15:13:11 -0500
From:	Sasha Levin <levinsasha928@...il.com>
To:	Pavel Emelyanov <xemul@...allels.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Michael Kerrisk <mtk.manpages@...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

On Thu, Feb 14, 2013 at 11:19 AM, Pavel Emelyanov <xemul@...allels.com> wrote:
> From: Stanislav Kinsbursky <skinsbursky@...allels.com>
>
> 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>
> Signed-off-by: Pavel Emelyanov <xemul@...allels.com>

Hi Pavel,

Why not use linux/hashtable.h?


Thanks,
Sasha
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