linux-kernel - Re: [PATCH v4 1/1] bus: mhi: host: Move IRQ allocation to controller registration phase

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Date:   Tue, 26 Jul 2022 13:39:13 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Kalle Valo <kvalo@...nel.org>
Cc:     Qiang Yu <quic_qianyu@...cinc.com>, quic_hemantk@...cinc.com,
        loic.poulain@...aro.org, quic_jhugo@...cinc.com,
        mhi@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, quic_cang@...cinc.com,
        ath11k@...ts.infradead.org
Subject: Re: [PATCH v4 1/1] bus: mhi: host: Move IRQ allocation to controller
 registration phase

On Mon, Jul 25, 2022 at 09:00:08PM +0300, Kalle Valo wrote:
> Manivannan Sadhasivam <mani@...nel.org> writes:
> 
> > On Wed, Jul 20, 2022 at 05:47:37PM +0800, Qiang Yu wrote:
> >
> >> 
> >> On 7/20/2022 5:39 PM, Manivannan Sadhasivam wrote:
> >> > On Mon, Jul 18, 2022 at 02:15:23PM +0300, Kalle Valo wrote:
> >> > > + ath11k list
> >> > > 
> >> > > Manivannan Sadhasivam <mani@...nel.org> writes:
> >> > > 
> >> > > > On Thu, Jun 23, 2022 at 10:43:03AM +0800, Qiang Yu wrote:
> >> > > > > During runtime, the MHI endpoint may be powered up/down several times.
> >> > > > > So instead of allocating and destroying the IRQs all the time, let's just
> >> > > > > enable/disable IRQs during power up/down.
> >> > > > > 
> >> > > > > The IRQs will be allocated during mhi_register_controller() and freed
> >> > > > > during mhi_unregister_controller(). This works well for things like PCI
> >> > > > > hotplug also as once the PCI device gets removed, the controller will
> >> > > > > get unregistered. And once it comes back, it will get registered back
> >> > > > > and even if the IRQ configuration changes (MSI), that will get accounted.
> >> > > > > 
> >> > > > > Signed-off-by: Qiang Yu <quic_qianyu@...cinc.com>
> >> > > > Applied to mhi-next!
> >> > > I did a bisect and this patch breaks ath11k during rmmod. I'm on
> >> > > vacation right now so I can't investigate in detail but more info below.
> >> > > 
> >> > I just tested linux-next/master next-20220718 on my NUC with QCA6390, but I'm
> >> > not able to reproduce the issue during rmmod! Instead I couldn't connect to AP.
> >> 
> >> I suspect that in __free_irq(), if CONFIG_DEBUG_SHIRQ is enabled, irq
> >> handler for a shared IRQ will be invoked and null pointer access happen.
> >> 
> >> #ifdef CONFIG_DEBUG_SHIRQ
> >>     /*
> >>      * It's a shared IRQ -- the driver ought to be prepared for an IRQ
> >>      * event to happen even now it's being freed, so let's make sure that
> >>      * is so by doing an extra call to the handler ....
> >>      *
> >>      * ( We do this after actually deregistering it, to make sure that a
> >>      *   'real' IRQ doesn't run in parallel with our fake. )
> >>      */
> >>     if (action->flags & IRQF_SHARED) {
> >>         local_irq_save(flags);
> >>         action->handler(irq, dev_id);
> >>         local_irq_restore(flags);
> >>     }
> >> #endif
> >> 
> >
> > Ah yes, after enabling CONFIG_DEBUG_SHIRQ I could reproduce the issue.
> 
> So how to fix this regression? (If there's already a fix I might have
> missed it as I came back only today)
> 

Copied you on the fix patch. Please test and let us know!

Thanks,
Mani

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> 
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