Il 08/05/23 09:44, Oliver Neukum ha scritto:
> On 04.05.23 13:35, AngeloGioacchino Del Regno wrote:
>
> Hi,
>
> looking at your patch I am afraid there is an issue.
>
>> In mtk_pcie_suspend_noirq() and mtk_pcie_resume_noirq() we are,
>> respectively, disabling and enabling generation of interrupts and
>> then saving and restoring the enabled interrupts register: since
>> we're using noirq PM callbacks, that can be safely done without
>> holding any spin lock.
>
> Why? You can still race with another CPU in task context.
> That is if you say that you do not need locking to touch
> PCIE_INT_ENABLE_REG that is fine, but then why do you remove
> it from one place only?
> It is also touched in mtk_pcie_probe() at a minimum.
>
>
>> That was noticed because of, and solves, the following issue:
>>
>> <4>[ 74.185982] ========================================================
>> <4>[ 74.192629] WARNING: possible irq lock inversion dependency detected
>> <4>[ 74.199276] 6.3.0-next-20230428+ #51 Tainted: G W
>> <4>[ 74.205664] --------------------------------------------------------
>> <4>[ 74.212309] systemd-sleep/809 just changed the state of lock:
>> <4>[ 74.218347] ffff65a5c34c65a0 (&pcie->irq_lock){+...}-{2:2}, at:
>> mtk_pcie_resume+0x50/0xa8
>> <4>[ 74.226870] but this lock was taken by another, HARDIRQ-safe lock in the past:
>> <4>[ 74.234389] (&irq_desc_lock_class){-.-.}-{2:2}
>> <4>[ 74.234409]
>> <4>[ 74.234409]
>> <4>[ 74.234409] and interrupts could create inverse lock ordering between them.
>> <4>[ 74.234409]
>> <4>[ 74.251704]
>> <4>[ 74.251704] other info that might help us debug this:
>> <4>[ 74.258785] Possible interrupt unsafe locking scenario:
>> <4>[ 74.258785]
>> <4>[ 74.266126] CPU0 CPU1
>> <4>[ 74.270942] ---- ----
>> <4>[ 74.275758] lock(&pcie->irq_lock);
>
> Lock A
>
>> <4>[ 74.279627] local_irq_disable();
>
> strictly speaking irrelevant
>
>> <4>[ 74.285836] lock(&irq_desc_lock_class);
>
> lock B
>
>> <4>[ 74.292667] lock(&pcie->irq_lock);
>
> lock A
>
>> <4>[ 74.299061] <Interrupt>
>
> You do not need that interrupt.
>
>> <4>[ 74.301960] lock(&irq_desc_lock_class);
>
> lock B
>
>> <4>[ 74.306438]
>> <4>[ 74.306438] *** DEADLOCK ***
Sorry for the very late reply. I just noticed this.
I'm unsure, at this point, about how to solve this warning; ideas?
Thanks,
Angelo