linux-kernel - Re: [patch 1/1] Switch ioctl functions of drivers/scsi/sg.c to unlocked

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Date:	Thu, 10 Jan 2008 13:03:48 -0600
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Andre Noll <maan@...temlinux.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	kernel-janitors@...r.kernel.org,
	Richard Knutsson <ricknu-0@...dent.ltu.se>
Subject: Re: [patch 1/1] Switch ioctl functions of drivers/scsi/sg.c to
	unlocked_ioctl


On Thu, 2008-01-10 at 19:59 +0100, Andi Kleen wrote:
> > Really, all this is doing is open coding what the ioctl handler is doing
> > anyway, isn't it? in which case, why bother to change it at all?
> 
> Because once it's open coded it is visible and can then be eliminated.
> Does SCSI need the BKL at all?

No, of course not ... it hasn't for ages, otherwise linux performance
would be in the tank.  If we require the BKL at all in the ioctl path it
will be to protect the non-SCSI structures we have to use.  Is there any
guide to which structures in the kernel still require the BKL?

> But perhaps for such a long ioctl handler it would be better to move
> the lock/unlock_kernel()s into the individual case ...: statements;
> then it could be eliminated step by step.

James


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