linux-kernel - Re: [PATCH v1 2/4] pinctrl: qcom: msm: Fix potential deadlock in pinmux configuration

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Message-ID: <z2oh7r56b7w3genfbq4jj24nvjehmnncufwwp6oj6duhafdaja@f2dle7jfao7e>
Date: Tue, 11 Nov 2025 09:35:43 -0600
From: Bjorn Andersson <andersson@...nel.org>
To: Praveen Talari <praveen.talari@....qualcomm.com>
Cc: Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Linus Walleij <linus.walleij@...aro.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Jiri Slaby <jirislaby@...nel.org>, Dmitry Baryshkov <lumag@...nel.org>, 
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-gpio@...r.kernel.org, linux-serial@...r.kernel.org, alexey.klimov@...aro.org, 
	krzk@...nel.org, bryan.odonoghue@...aro.org, jorge.ramirez@....qualcomm.com, 
	dmitry.baryshkov@....qualcomm.com, Konrad Dybcio <konrad.dybcio@....qualcomm.com>, 
	psodagud@...cinc.com, djaggi@...cinc.com, quic_msavaliy@...cinc.com, 
	quic_vtanuku@...cinc.com, quic_arandive@...cinc.com, quic_shazhuss@...cinc.com, 
	quic_cchiluve@...cinc.com, Prasad Sodagudi <prasad.sodagudi@....qualcomm.com>
Subject: Re: [PATCH v1 2/4] pinctrl: qcom: msm: Fix potential deadlock in
 pinmux configuration

On Tue, Nov 11, 2025 at 10:52:25AM +0530, Praveen Talari wrote:
> Hi Bjorn,
> 
> Thank you for review.
> 
> On 11/11/2025 9:38 AM, Bjorn Andersson wrote:
> > On Mon, Nov 10, 2025 at 03:40:41PM +0530, Praveen Talari wrote:
> > > Replace disable_irq() with disable_irq_nosync() in msm_pinmux_set_mux()
> > > to prevent potential deadlock when wakeup IRQ is triggered on the same
> > 
> > "potential"? In what case will calling disable_irq() from the irq
> > handler of that irq not deadlock?
> > 
> > > GPIO being reconfigured.
> > > 
> > > The issue occurs when a wakeup IRQ is triggered on a GPIO and the IRQ
> > > handler attempts to reconfigure the same GPIO's pinmux. In this scenario,
> > > msm_pinmux_set_mux() calls disable_irq() which waits for the currently
> > > running IRQ handler to complete, creating a circular dependency that
> > > results in deadlock.
> > > 
> > > Using disable_irq_nosync() avoids waiting for the IRQ handler to
> > > complete, preventing the deadlock condition while still properly
> > > disabling the interrupt during pinmux reconfiguration.
> > > 
> > > Suggested-by: Prasad Sodagudi <prasad.sodagudi@....qualcomm.com>
> > 
> > That's weird, I debugged your deadlock for you and told you to make this
> > very change in:
> > 
> > https://lore.kernel.org/all/7sxsfyu2kqbycyfftwfhrncwk3dfnubmzhyi2rqi3jtvi5qsnh@bya3cii45zhn/
> > 
> > So I guess Prasad told you how to fix this issue before I invested the
> > time helping you?
> 
> Yes, that’s correct. Prasad had suggested it earlier.
> 

Okay, then this patch looks good.

Regards,
Bjorn

> Thanks,
> Praveen Talari
> 
> > 
> > 
> > Change looks good, and description captures the problem.
> > 
> > Reviewed-by: Bjorn Andersson <andersson@...nel.org>
> > 
> > Regards,
> > Bjorn
> > 
> > > Signed-off-by: Praveen Talari <praveen.talari@....qualcomm.com>
> > > ---
> > >   drivers/pinctrl/qcom/pinctrl-msm.c | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/pinctrl/qcom/pinctrl-msm.c b/drivers/pinctrl/qcom/pinctrl-msm.c
> > > index 67525d542c5b..e99871b90ab9 100644
> > > --- a/drivers/pinctrl/qcom/pinctrl-msm.c
> > > +++ b/drivers/pinctrl/qcom/pinctrl-msm.c
> > > @@ -189,7 +189,7 @@ static int msm_pinmux_set_mux(struct pinctrl_dev *pctldev,
> > >   	 */
> > >   	if (d && i != gpio_func &&
> > >   	    !test_and_set_bit(d->hwirq, pctrl->disabled_for_mux))
> > > -		disable_irq(irq);
> > > +		disable_irq_nosync(irq);
> > >   	raw_spin_lock_irqsave(&pctrl->lock, flags);
> > > -- 
> > > 2.34.1
> > >