[PATCH v2 00/10] Refine the locking for dev->iommu_group

Marek Szyprowski m.szyprowski at samsung.com
Tue Aug 8 07:51:57 PDT 2023

Hi Jason,

On 08.08.2023 16:30, Jason Gunthorpe wrote:
> On Tue, Aug 08, 2023 at 04:02:40PM +0200, Marek Szyprowski wrote:
>> On 08.08.2023 15:25, Jason Gunthorpe wrote:
>>> On Tue, Aug 08, 2023 at 03:08:30PM +0200, Marek Szyprowski wrote:
>>>>> Any of the drivers that use platform device as the iommu_device will
>>>>> have a problem, please try:
>>>>> https://lore.kernel.org/linux-iommu/ZNIz%2FNVLb6WqqvQx@nvidia.com/
>>>> I've checked and it doesn't help in my case. I will soon check why.
>>> Oh, I botched it. Forgot that the iommu_device->dev is the sysfs
>>> handle not the HW device. Maybe this:
>> This fixed the early lockup, but then system hangs again a bit later. It
>> looks that this device lock in __iommu_probe_device() is really
>> problematic,
> Yes, I expected we'd hit something like this - I checked alot of call
> paths but missed these two. The self-probe is sneaky, but here the
> device_lock is held way up the call chain, I just missed it.
> The fix is to just annotate that we already hold the lock when calling
> iommu_probe_device(), since we know in those cases that we must be
> holding it:

Great, this fixed the issue. Feel free to add:

Tested-by: Marek Szyprowski <m.szyprowski at samsung.com>

 > ...

Best regards
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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