linux-kernel - Re: [RFC][PATCH] spinlock: Kill spin_unlock

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Message-ID: <20110107213302.GI7355@mtj.dyndns.org>
Date:	Fri, 7 Jan 2011 16:33:02 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Jeff Garzik <jeff@...zik.org>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Nick Piggin <npiggin@...nel.dk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Chris Mason <chris.mason@...cle.com>,
	Frank Rowand <frank.rowand@...sony.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Galbraith <efault@....de>,
	Oleg Nesterov <oleg@...hat.com>, Paul Turner <pjt@...gle.com>,
	Jens Axboe <axboe@...nel.dk>,
	Yong Zhang <yong.zhang0@...il.com>,
	linux-kernel@...r.kernel.org,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	IDE/ATA development list <linux-ide@...r.kernel.org>
Subject: Re: [RFC][PATCH] spinlock: Kill spin_unlock_wait()

Hello, Jeff.

On Fri, Jan 07, 2011 at 04:13:53PM -0500, Jeff Garzik wrote:
> > Hmm... I think the ->eng_timeout path is already dead.  We no longer
> > have any in-kernel implementation, so killing spin_unlock_wait()
> > should be fine.  I'll follow up with removal of the unused callback.
> 
> Unfortunately...  libsas continues to avoid the new EH :(
> 
> It's a hairy mess to untangle, too.  libata does proper error handling
> of ATA device errors, notably NCQ error handling, which libsas sorely
> misses.  But libata new EH assumes a bit too much about "owning" the
> entirety of the EH process.  These assumptions are proper for wholly
> ATA drivers (drivers/ata/*) where new EH can drive the EH process, but
> in the SAS situation, a phy in SATA mode is simply a subset of a
> larger set of EH conditions that must be handled.
> 
> Thus libsas uses the ancient libata hook ->phy_reset and lacks ->error_handler.
> 
> I think libata's old-EH path is entirely SAS-specific at this point.

Hmm... but they don't use ata_scsi_error() and ->eng_timeout() at all,
no?  We can't remove phy_reset() and need to keep the silly "if
(->error_handler)" tests around but should be able to remove those
from ata_scsi_error() and other EH routines, at least.  Am I missing
something?

Thanks.

-- 
tejun
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