linux-kernel - Re: [PATCH 1/3] mpt2sas: remove the use of writeq, since writeq is not atomic

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Message-ID: <BANLkTin4w1QyL1NyTyrZARPWASai45W_4Q@mail.gmail.com>
Date:	Thu, 19 May 2011 13:08:38 +0900
From:	Hitoshi Mitake <h.mitake@...il.com>
To:	"Moore, Eric" <Eric.Moore@....com>
Cc:	Milton Miller <miltonm@....com>, Sam Ravnborg <sam@...nborg.org>,
	Ingo Molnar <mingo@...e.hu>, Ingo Molnar <mingo@...hat.com>,
	"Desai, Kashyap" <Kashyap.Desai@....com>,
	"Prakash, Sathya" <Sathya.Prakash@....com>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Matthew Wilcox <matthew@....cx>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linux scsi dev <linux-scsi@...r.kernel.org>,
	"paulus@...ba.org" <paulus@...ba.org>,
	linux powerpc dev <linuxppc-dev@...ts.ozlabs.org>,
	linux pci <linux-pci@...r.kernel.org>,
	linux kernel <linux-kernel@...r.kernel.org>,
	linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 1/3] mpt2sas: remove the use of writeq, since writeq is
 not atomic

On Thu, May 19, 2011 at 04:11, Moore, Eric <Eric.Moore@....com> wrote:
> On Wednesday, May 18, 2011 12:31 PM Milton Miller wrote:
>> Ingo I would propose the following commits added in 2.6.29 be reverted.
>> I think the current concensus is drivers must know if the writeq is
>> not atomic so they can provide their own locking or other workaround.
>>
>
>
> Exactly.
>

The original motivation of preparing common readq/writeq is that
letting each driver
have their own readq/writeq is bad for maintenance of source code.

But if you really dislike them, there might be two solutions:

1. changing the name of readq/writeq to readq_nonatomic/writeq_nonatomic
2. adding new C file to somewhere and defining spinlock for them.
    With spin_lock_irqsave() and spin_unlock_irqrestore() on the spinlock,
    readq/writeq can be atomic.

How do you think about them? If you cannot agree with the above two solutions,
I'll agree with reverting them.

-- 
Hitoshi Mitake
h.mitake@...il.com
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