linux-kernel - Re: Async resume patch (was: Re: [GIT PULL] PM updates for 2.6.33)

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Message-ID: <alpine.LFD.2.00.0912080728590.3560@localhost.localdomain>
Date:	Tue, 8 Dec 2009 07:35:27 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Alan Stern <stern@...land.harvard.edu>,
	Zhang Rui <rui.zhang@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: Async resume patch (was: Re: [GIT PULL] PM updates for 2.6.33)

On Tue, 8 Dec 2009, Rafael J. Wysocki wrote:
> 
> The wait queue plus the op_complete flag combo plays the role of the locking
> in the Linus' picture

Please just use the lock. Don't make up your own locking crap. Really. 

Your patch is horrible. Exactly because your locking is horribly 
mis-designed. You can't say things are complete from an interrupt, for 
example, since you made it some random bitfield, which has unknown 
characteristics (ie non-atomic read-modify-write etc).

The fact is, any time anybody makes up a new locking mechanism, THEY 
ALWAYS GET IT WRONG. Don't do it.

I suggested using the rwsem locking for a good reason. It made sense. It 
was simpler. Just do it that way, stop making up crap.

		Linus
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