linux-kernel - Re: [PATCH 5.10 012/105] dmaengine: shdma: Fix runtime PM imbalance on error

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Message-ID: <20220309135708.GB30506@duo.ucw.cz>
Date:   Wed, 9 Mar 2022 14:57:08 +0100
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Pavel Machek <pavel@...x.de>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Yongzhi Liu <lyz_cs@....edu.cn>,
        Vinod Koul <vkoul@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.10 012/105] dmaengine: shdma: Fix runtime PM imbalance
 on error

On Wed 2022-03-09 14:40:56, Greg Kroah-Hartman wrote:
> On Wed, Mar 09, 2022 at 01:35:09PM +0100, Pavel Machek wrote:
> > On Wed 2022-03-09 12:58:46, Greg Kroah-Hartman wrote:
> > > On Wed, Mar 09, 2022 at 11:54:20AM +0100, Pavel Machek wrote:
> > > > Hi!
> > > > 
> > > > > From: Yongzhi Liu <lyz_cs@....edu.cn>
> > > > > 
> > > > > [ Upstream commit 455896c53d5b803733ddd84e1bf8a430644439b6 ]
> > > > > 
> > > > > pm_runtime_get_() increments the runtime PM usage counter even
> > > > > when it returns an error code, thus a matching decrement is needed on
> > > > > the error handling path to keep the counter balanced.
> > > > 
> > > > This patch will break things.
> > > > 
> > > > Notice that -ret is ignored (checked 4.4 and 5.10), so we don't
> > > > actually abort/return error; we just printk. We'll do two
> > > > pm_runtime_put's after the "fix".
> > > > 
> > > > Please drop from -stable.
> > > > 
> > > > It was discussed during AUTOSEL review:
> > > > 
> > > > Date: Fri, 25 Feb 2022 14:25:10 +0800 (GMT+08:00)
> > > > From: 刘永志 <lyz_cs@....edu.cn>
> > > > To: pavel machek <pavel@...x.de>
> > > > Cc: sasha levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
> > > > Subject: Re: [PATCH AUTOSEL 5.16 24/30] dmaengine: shdma: Fix runtime PM
> > > > 	imbalance on error
> > > 
> > > So 5.15 and 5.16 is ok, but older is not?
> > 
> > I believe commit is wrong for mainline and all stable releases, and
> > author seems to agree. Drop from everywhere.
> 
> Is it reverted in Linus's tree yet?

It will take you a minute to check.

Take a look at the patch. There's no return in error path, thus doing
runtime_put is clearly bogus. Should take you less than minute to
verify.

Please drop the patch.
								Pavel
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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