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From: Richard Weinberger <richard@nod.at>
To: "Bityutskiy, Artem" <artem.bityutskiy@intel.com>
Cc: "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"dedekind1@gmail.com" <dedekind1@gmail.com>
Subject: Re: [PATCH 4/4] UBI: Fastmap: Ensure that only one fastmap work is scheduled
Date: Tue, 30 Sep 2014 09:44:36 +0200	[thread overview]
Message-ID: <542A5F64.5000302@nod.at> (raw)
In-Reply-To: <1412062762.2379.2.camel@sauron.fi.intel.com>

Am 30.09.2014 09:39, schrieb Bityutskiy, Artem:
> On Tue, 2014-09-30 at 08:59 +0200, Richard Weinberger wrote:
>> Am 30.09.2014 08:45, schrieb Bityutskiy, Artem:
>>> On Tue, 2014-09-30 at 00:20 +0200, Richard Weinberger wrote:
>>>> +       spin_lock(&ubi->wl_lock);
>>>> +       ubi->fm_work_scheduled = 0;
>>>> +       spin_unlock(&ubi->wl_lock);
>>>
>>> Andrew Morton once said me that if I am protecting an integer change
>>> like this with a spinlock, I have a problem in my locking design. He was
>>> right for my particular case.
>>>
>>> Integer is changes atomic. The only other thing spinlock adds are the
>>> barriers.
>>
>> I've added the spinlock to have a barrier in any case.
> 
> Examples of any?

You mean a case where the compiler would reorder code and the barrier is needed?
I don't have one, but I'm not that creative as a modern C compiler.
If you say that no barrier is needed I'll trust you. :-)

Thanks,
//richard

WARNING: multiple messages have this Message-ID (diff)
From: Richard Weinberger <richard@nod.at>
To: "Bityutskiy, Artem" <artem.bityutskiy@intel.com>
Cc: "dedekind1@gmail.com" <dedekind1@gmail.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>
Subject: Re: [PATCH 4/4] UBI: Fastmap: Ensure that only one fastmap work is scheduled
Date: Tue, 30 Sep 2014 09:44:36 +0200	[thread overview]
Message-ID: <542A5F64.5000302@nod.at> (raw)
In-Reply-To: <1412062762.2379.2.camel@sauron.fi.intel.com>

Am 30.09.2014 09:39, schrieb Bityutskiy, Artem:
> On Tue, 2014-09-30 at 08:59 +0200, Richard Weinberger wrote:
>> Am 30.09.2014 08:45, schrieb Bityutskiy, Artem:
>>> On Tue, 2014-09-30 at 00:20 +0200, Richard Weinberger wrote:
>>>> +       spin_lock(&ubi->wl_lock);
>>>> +       ubi->fm_work_scheduled = 0;
>>>> +       spin_unlock(&ubi->wl_lock);
>>>
>>> Andrew Morton once said me that if I am protecting an integer change
>>> like this with a spinlock, I have a problem in my locking design. He was
>>> right for my particular case.
>>>
>>> Integer is changes atomic. The only other thing spinlock adds are the
>>> barriers.
>>
>> I've added the spinlock to have a barrier in any case.
> 
> Examples of any?

You mean a case where the compiler would reorder code and the barrier is needed?
I don't have one, but I'm not that creative as a modern C compiler.
If you say that no barrier is needed I'll trust you. :-)

Thanks,
//richard


  reply	other threads:[~2014-09-30  7:45 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-29 22:20 UBI: Fastmap fixes - round one Richard Weinberger
2014-09-29 22:20 ` [PATCH 1/4] UBI: Ensure that all fastmap work is done upon WL shutdown Richard Weinberger
2014-09-29 22:20   ` Richard Weinberger
2014-09-30  6:26   ` Artem Bityutskiy
2014-09-30  6:58     ` Richard Weinberger
2014-09-30  7:53       ` Bityutskiy, Artem
2014-09-30  7:53         ` Bityutskiy, Artem
2014-09-30  8:07         ` Richard Weinberger
2014-09-30  8:07           ` Richard Weinberger
2014-10-03 12:52           ` Artem Bityutskiy
2014-10-03 12:52             ` Artem Bityutskiy
2014-10-02 13:05   ` Tanya Brokhman
2014-10-02 13:18     ` Richard Weinberger
2014-10-02 13:38       ` Tanya Brokhman
2014-09-29 22:20 ` [PATCH 2/4] UBI: Fastmap: Calc fastmap size correctly Richard Weinberger
2014-09-29 22:20   ` Richard Weinberger
2014-10-02 13:14   ` Tanya Brokhman
2014-10-02 13:18     ` Richard Weinberger
2014-10-02 14:04   ` Tanya Brokhman
2014-10-03 14:38   ` Artem Bityutskiy
2014-09-29 22:20 ` [PATCH 3/4] UBI: Fastmap: Care about the protection queue Richard Weinberger
2014-09-29 22:20   ` Richard Weinberger
2014-10-02 13:28   ` Tanya Brokhman
2014-10-02 13:32     ` Richard Weinberger
2014-10-02 14:14       ` Tanya Brokhman
2014-10-03 14:31   ` Artem Bityutskiy
2014-10-03 19:06     ` Richard Weinberger
2014-10-13 13:17       ` Artem Bityutskiy
2014-10-13 14:30         ` Richard Weinberger
2014-10-13 15:23           ` Artem Bityutskiy
2014-10-13 15:28             ` Bityutskiy, Artem
2014-10-13 15:28               ` Bityutskiy, Artem
2014-10-13 21:04             ` Richard Weinberger
2014-10-14 10:23               ` Artem Bityutskiy
2014-10-14 12:21                 ` Tanya Brokhman
2014-10-14 13:02                   ` Artem Bityutskiy
2014-10-14 13:35                     ` Tanya Brokhman
2014-10-16 10:06                 ` Richard Weinberger
2014-10-16 10:15                   ` Artem Bityutskiy
2014-10-16 11:07                     ` Richard Weinberger
2014-10-20 14:46                   ` Artem Bityutskiy
2014-10-20 15:17                     ` Richard Weinberger
2014-10-20 15:40                       ` Artem Bityutskiy
2014-10-20 15:59                         ` Richard Weinberger
2014-10-20 16:09                           ` Artem Bityutskiy
2014-10-20 16:17                             ` Richard Weinberger
2014-10-20 20:46                         ` Richard Weinberger
2014-09-29 22:20 ` [PATCH 4/4] UBI: Fastmap: Ensure that only one fastmap work is scheduled Richard Weinberger
2014-09-29 22:20   ` Richard Weinberger
2014-09-30  6:45   ` Bityutskiy, Artem
2014-09-30  6:45     ` Bityutskiy, Artem
2014-09-30  6:59     ` Richard Weinberger
2014-09-30  6:59       ` Richard Weinberger
2014-09-30  7:39       ` Bityutskiy, Artem
2014-09-30  7:39         ` Bityutskiy, Artem
2014-09-30  7:44         ` Richard Weinberger [this message]
2014-09-30  7:44           ` Richard Weinberger
2014-10-02 14:22           ` Tanya Brokhman

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