[v2] dmaengine: idxd: Fix refcount and cleanup issues on module unload

[PATCH v2 2/2] dmaengine: idxd: Fix refcount underflow on module unload

Posted by Yi Sun 6 months, 2 weeks ago

A recent refactor introduced a misplaced put_device() call, leading to a
reference count underflow during module unload.

There is no need to add additional put_device() calls for idxd groups,
engines, or workqueues. Although commit a409e919ca3 claims:"Note, this
also fixes the missing put_device() for idxd groups, engines, and wqs."
It appears no such omission existed. The required cleanup is already
handled by the call chain:
idxd_unregister_devices() -> device_unregister() -> put_device()

Extend idxd_cleanup() to perform the necessary cleanup, and remove
idxd_cleanup_internals() which was not originally part of the driver
unload path and introduced unintended reference count underflow.

Fixes: a409e919ca32 ("dmaengine: idxd: Refactor remove call with idxd_cleanup() helper")
Signed-off-by: Yi Sun <yi.sun@intel.com>

diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index 504aca0fd597..a5eabeb6a8bd 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -1321,7 +1321,12 @@ static void idxd_remove(struct pci_dev *pdev)
 	device_unregister(idxd_confdev(idxd));
 	idxd_shutdown(pdev);
 	idxd_device_remove_debugfs(idxd);
-	idxd_cleanup(idxd);
+	perfmon_pmu_remove(idxd);
+	idxd_cleanup_interrupts(idxd);
+	if (device_pasid_enabled(idxd))
+		idxd_disable_system_pasid(idxd);
+	if (device_user_pasid_enabled(idxd))
+		idxd_disable_sva(idxd->pdev);
 	pci_iounmap(pdev, idxd->reg_base);
 	put_device(idxd_confdev(idxd));
 	pci_disable_device(pdev);
-- 
2.43.0

Re: [PATCH v2 2/2] dmaengine: idxd: Fix refcount underflow on module unload

Posted by Vinicius Costa Gomes 6 months, 1 week ago

Yi Sun <yi.sun@intel.com> writes:

> A recent refactor introduced a misplaced put_device() call, leading to a
> reference count underflow during module unload.
>
> There is no need to add additional put_device() calls for idxd groups,
> engines, or workqueues. Although commit a409e919ca3 claims:"Note, this
> also fixes the missing put_device() for idxd groups, engines, and wqs."
> It appears no such omission existed. The required cleanup is already
> handled by the call chain:
> idxd_unregister_devices() -> device_unregister() -> put_device()
>
> Extend idxd_cleanup() to perform the necessary cleanup, and remove
> idxd_cleanup_internals() which was not originally part of the driver
> unload path and introduced unintended reference count underflow.
>
> Fixes: a409e919ca32 ("dmaengine: idxd: Refactor remove call with idxd_cleanup() helper")
> Signed-off-by: Yi Sun <yi.sun@intel.com>
>
> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
> index 504aca0fd597..a5eabeb6a8bd 100644
> --- a/drivers/dma/idxd/init.c
> +++ b/drivers/dma/idxd/init.c
> @@ -1321,7 +1321,12 @@ static void idxd_remove(struct pci_dev *pdev)
>  	device_unregister(idxd_confdev(idxd));
>  	idxd_shutdown(pdev);
>  	idxd_device_remove_debugfs(idxd);
> -	idxd_cleanup(idxd);
> +	perfmon_pmu_remove(idxd);
> +	idxd_cleanup_interrupts(idxd);
> +	if (device_pasid_enabled(idxd))
> +		idxd_disable_system_pasid(idxd);
> +	if (device_user_pasid_enabled(idxd))
> +		idxd_disable_sva(idxd->pdev);

idxd_disable_sva() got removed in commit 853b01b5efd7 ("dmaengine: idxd:
Remove unnecessary IOMMU_DEV_FEAT_IOPF")

>  	pci_iounmap(pdev, idxd->reg_base);
>  	put_device(idxd_confdev(idxd));
>  	pci_disable_device(pdev);
> -- 
> 2.43.0
>


Cheers,
-- 
Vinicius

Re: [PATCH v2 2/2] dmaengine: idxd: Fix refcount underflow on module unload

Posted by Yi Sun 6 months, 1 week ago

On 13.06.2025 16:20, Vinicius Costa Gomes wrote:
>Yi Sun <yi.sun@intel.com> writes:
>
>> A recent refactor introduced a misplaced put_device() call, leading to a
>> reference count underflow during module unload.
>>
>> There is no need to add additional put_device() calls for idxd groups,
>> engines, or workqueues. Although commit a409e919ca3 claims:"Note, this
>> also fixes the missing put_device() for idxd groups, engines, and wqs."
>> It appears no such omission existed. The required cleanup is already
>> handled by the call chain:
>> idxd_unregister_devices() -> device_unregister() -> put_device()
>>
>> Extend idxd_cleanup() to perform the necessary cleanup, and remove
>> idxd_cleanup_internals() which was not originally part of the driver
>> unload path and introduced unintended reference count underflow.
>>
>> Fixes: a409e919ca32 ("dmaengine: idxd: Refactor remove call with idxd_cleanup() helper")
>> Signed-off-by: Yi Sun <yi.sun@intel.com>
>>
>> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
>> index 504aca0fd597..a5eabeb6a8bd 100644
>> --- a/drivers/dma/idxd/init.c
>> +++ b/drivers/dma/idxd/init.c
>> @@ -1321,7 +1321,12 @@ static void idxd_remove(struct pci_dev *pdev)
>>  	device_unregister(idxd_confdev(idxd));
>>  	idxd_shutdown(pdev);
>>  	idxd_device_remove_debugfs(idxd);
>> -	idxd_cleanup(idxd);
>> +	perfmon_pmu_remove(idxd);
>> +	idxd_cleanup_interrupts(idxd);
>> +	if (device_pasid_enabled(idxd))
>> +		idxd_disable_system_pasid(idxd);
>> +	if (device_user_pasid_enabled(idxd))
>> +		idxd_disable_sva(idxd->pdev);
>
>idxd_disable_sva() got removed in commit 853b01b5efd7 ("dmaengine: idxd:
>Remove unnecessary IOMMU_DEV_FEAT_IOPF")
I get it, thanks Vinicius for the reminder. Will post another version.

Thanks
    --Sun, Yi