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

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Message-ID: <511DC3EF.60904@parallels.com>
Date:	Fri, 15 Feb 2013 09:13:19 +0400
From:	Pavel Emelyanov <xemul@...allels.com>
To:	Sasha Levin <levinsasha928@...il.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 02/15/2013 12:13 AM, Sasha Levin wrote:
> 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?

Simply because this patch was just picked from the previous discussions
as is :) I will tune it to use hashtable.h in the next iteration.

> 
> Thanks,
> Sasha
> .
> 


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