linux-kernel - Re: [PATCH 2/3] dmaengine: usb-dmac: Fix PM reference leak in usb_dmac

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Message-ID: <YL3TlDqe4KSr3ICl@hovoldconsulting.com>
Date:   Mon, 7 Jun 2021 10:06:44 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     "yukuai (C)" <yukuai3@...wei.com>, mcoquelin.stm32@...il.com,
        alexandre.torgue@...s.st.com, michal.simek@...inx.com,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, yi.zhang@...wei.com
Subject: Re: [PATCH 2/3] dmaengine: usb-dmac: Fix PM reference leak in
 usb_dmac_probe()

On Thu, Jun 03, 2021 at 04:39:08PM +0530, Vinod Koul wrote:
> On 31-05-21, 11:19, Johan Hovold wrote:
> > On Mon, May 31, 2021 at 02:27:34PM +0530, Vinod Koul wrote:
> > > On 31-05-21, 14:11, yukuai (C) wrote:
> > > > On 2021/05/31 12:00, Vinod Koul wrote:
> > > > > On 17-05-21, 16:18, Yu Kuai wrote:
> > > > > > pm_runtime_get_sync will increment pm usage counter even it failed.
> > > > > > Forgetting to putting operation will result in reference leak here.
> > > > > > Fix it by replacing it with pm_runtime_resume_and_get to keep usage
> > > > > > counter balanced.

> > > Yes the rumtime_pm is disabled on failure here and the count would have
> > > no consequence...
> > 
> > You should still balance the PM usage counter as it isn't reset for
> > example when reloading the driver.
> 
> Should I driver trust that on load PM usage counter is balanced and not
> to be reset..?

Not sure what you're asking here. But a driver should never leave the PM
usage counter unbalanced.

> > Using pm_runtime_resume_and_get() is one way of handling this, but
> > alternatively you could also move the error_pm label above the
> > pm_runtime_put() in the error path.
> 
> That would be a better way I think

Johan