Re: [PATCH 7/7] cxl: Fix double unregistration of CXL regions for type2 devices

[Dave Jiang <dave.jiang@intel.com>]

On 4/23/26 12:10 AM, Alejandro Lucero Palau wrote:
> 
> On 4/23/26 00:02, Dave Jiang wrote:
>> For a type2 device cxl_memdev_attach_region() is provided as the callback
>> to devm_cxl_add_memdev() call. In cxl_memdev_attach_region() a devm
>> action cxl_endpoint_region_autoremove() is registered to remove the
>> region when the device is removed. And this action calls
>> unregister_region() on trigger.
>>
>> When the endpoint port driver is probed, discover_region() is called
>> to register a region. The call tree becomes discover_region() ->
>> cxl_add_to_region() -> construct_region() -> __create_region() ->
>> devm_cxl_add_region(). In devm_cxl_add_region(), unregister_region()
>> is also added as a devm action.
>>
>> When removing the cxl_test module, the platform devices are removed
>> and that triggers the endpoint driver removal and calling of
>> unregister_region(). And then when the mock type2 device driver is being
>> removed, the devm action of unregister_region() is called again, which
>> causes a kernel warning about double unregistration of the same region.
>> Add a check to see if the devm action is already removed before calling
>> unregister_region() for cxl_endpoint_region_autoremove().
>>
>> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
>>
>> ---
>> - Need to add a fixes tag when the patch commit that introduces
>>    cxl_endpoint_region_autoremove() is stable.
>> ---
>>   drivers/cxl/core/region.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>> index 61a3efdbf3c9..1a7c0895bb88 100644
>> --- a/drivers/cxl/core/region.c
>> +++ b/drivers/cxl/core/region.c
>> @@ -4296,7 +4296,8 @@ static void cxl_endpoint_region_autoremove(void *_cxlr)
>>       struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
>>       struct cxl_port *port = cxlrd_to_port(cxlrd);
>>   -    devm_release_action(port->uport_dev, unregister_region, cxlr);
>> +    if (!devm_remove_action_nowarn(port->uport_dev, unregister_region, cxlr))
>> +        unregister_region(cxlr);
>>   }
>>     /*
> 
> 
> Hi Dave,
> 
> 
> Yes, I saw that problem and reported to Dan:
> 
> 
> https://lore.kernel.org/linux-cxl/20260403210050.1058650-1-dan.j.williams@intel.com/T/#m467dc88199645865a05b5fef858a67f3a608895b
> 
> 
> I thought about adding similar check in my impending v26 but I ended up changing the linking of the created region from the root port to the endpoint device only. This avoids the problem you report for the cases of removing cxl_acpi before accelerator driver or cxl_mem unbinding the accelerator memdev.
> 
> 
> You will see that later today within v26.
> 

Thanks. This series will adapt to whatever the final resulting version we merge upstream.
> 
> Thank you.
>