Re: [PATCH] pci: tegra194: Fix debugfs cleanup for !CONFIG_PCIEASPM

[Hans Zhang <18255117159@163.com>]

On 2025/4/6 00:17, Christophe JAILLET wrote:
> Le 05/04/2025 à 17:49, Hans Zhang a écrit :
>>
>>
>> On 2025/4/5 23:28, Bjorn Helgaas wrote:
>>> Follow subject line capitalization convention.
>>>
>>> On Sat, Apr 05, 2025 at 10:54:59PM +0800, Hans Zhang wrote:
>>>> When CONFIG_PCIEASPM is disabled, debugfs entries are not created, but
>>>> tegra_pcie_dw_remove() and tegra_pcie_dw_shutdown() unconditionally 
>>>> call
>>>> debugfs_remove_recursive(), leading to potential NULL pointer 
>>>> operations.
>>>>
>>>> Introduce deinit_debugfs() to wrap debugfs_remove_recursive(), which is
>>>> stubbed for !CONFIG_PCIEASPM. Use this function during removal/ 
>>>> shutdown to
>>>> ensure debugfs cleanup only occurs when entries were initialized.
>>>>
>>>> This prevents kernel warnings and instability when ASPM support is
>>>> disabled.
>>>
>>> This looks like there should be a Fixes: tag to connect this to the
>>> commit that introduced the problem.
>>
>> Hi Bjorn,
>>
>> Thanks your for reply. Will add.
>>
>> Fixes: bb617cbd8151 (PCI: tegra194: Clean up the exit path for 
>> Endpoint mode)
>>
>>>
>>> If this is something that broke with the v6.15 merge window, we should
>>> include this in v6.15 via pci/for-linus.  If this broke earlier, we
>>> would have to decide whether pci/for-linus is still appropriate or a
>>> stable tag.
>>>
>>
>> The original code that introduced the unconditional 
>> `debugfs_remove_recursive()` calls was actually merged in an earlier 
>> cycle.
>>
>>> We did merge some debugfs things for v6.15, but I don't see anything
>>> specific to pcie-tegra194.c, so I'm confused about why this fix would
>>> be in pcie-tegra194.c instead of some more generic place.
>>>
>>
>> The Tegra194 driver conditionally initializes pcie->debugfs based on 
>> CONFIG_PCIEASPM. When ASPM is disabled, pcie->debugfs remains 
>> uninitialized, but tegra_pcie_dw_remove() and tegra_pcie_dw_shutdown() 
>> unconditionally call debugfs_remove_recursive(), leading to a NULL 
> 
> debugfs IS initialized, because it is in a structure allocated with 
> devm_kzalloc().
> 
> And debugfs functions handle such cases.
> 

Oh, my mind went wrong and I didn't pay attention to devm, and I'm 
really sorry about that.

Another problem I noticed here is that currently, no matter what, 
pcie->debugfs = debugfs_create_dir(name, NULL) is executed; if #if 
defined(CONFIG_PCIEASPM) is valid, then pcie->debugfs = 
debugfs_create_dir(name, NULL); Is it superfluous?

Best regards,
Hans