linux-kernel - Re: [PATCH 4/4] UBI: Fastmap: Ensure that only one fastmap work is scheduled

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Message-ID: <542A5F64.5000302@nod.at>
Date:	Tue, 30 Sep 2014 09:44:36 +0200
From:	Richard Weinberger <richard@....at>
To:	"Bityutskiy, Artem" <artem.bityutskiy@...el.com>
CC:	"dedekind1@...il.com" <dedekind1@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>
Subject: Re: [PATCH 4/4] UBI: Fastmap: Ensure that only one fastmap work is
 scheduled

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

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