Re: [PATCH v2] PCI: pciehp: Fix re-enabling the slot marked for safe removal

From: Sergey Miroshnichenko <s.miroshnichenko@yadro.com>
To: Lukas Wunner <lukas@wunner.de>
Cc: <linux-pci@vger.kernel.org>, <linux@yadro.com>
Subject: Re: [PATCH v2] PCI: pciehp: Fix re-enabling the slot marked for safe removal
Date: Wed, 13 Mar 2019 16:42:00 +0300	[thread overview]
Message-ID: <b1a7f0b6-2bbf-213d-0f56-bc828922dfed@yadro.com> (raw)
In-Reply-To: <20190312122014.jrwgnqpuiywb7xsd@wunner.de>

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On 3/12/19 3:20 PM, Lukas Wunner wrote:
> On Tue, Mar 12, 2019 at 03:05:48PM +0300, Sergey Miroshnichenko wrote:
>> During the safe removal procedure, a Data Link Layer State Changed event
>> may occur after pciehp_power_off_slot(), and it is handled when the slot is
>> already set to OFF_STATE. This results in re-enabling the device and makes
>> it impossible to actually safely remove it.
>>
>> Clear out the Presence Detect Changed and Data Link Layer State Changed
>> events when the disabled slot has settled down.
>>
>> It is still possible to re-enable the device if it remains in the slot
>> after pressing the Attention Button by pressing it again.
>>
>> Signed-off-by: Sergey Miroshnichenko <s.miroshnichenko@yadro.com>
> 
> Reviewed-by: Lukas Wunner <lukas@wunner.de>
> 

Thank you!

> Did this work correctly before v4.19 or is it a regression caused by
> d331710ea78f ("PCI: pciehp: Become resilient to missed events")?
> Either way, it seems reasonable to backport it to stable and
> v4.19 is the earliest that it should apply cleanly to, so:
> 
> Cc: stable@vger.kernel.org # v4.19+
> 

Yes, that was a regression caused by this commit. I've verified it
applies cleanly to v4.19.

Best regards,
Serge

> Thanks a lot for catching this, I wasn't able to test the code paths
> which are only exercised if a power controller is present (because
> Thunderbolt doesn't have one).
> 
> Lukas
> 
>> ---
>>  drivers/pci/hotplug/pciehp_ctrl.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
>> index 3f3df4c29f6e..905282a8ddaa 100644
>> --- a/drivers/pci/hotplug/pciehp_ctrl.c
>> +++ b/drivers/pci/hotplug/pciehp_ctrl.c
>> @@ -115,6 +115,10 @@ static void remove_board(struct controller *ctrl, bool safe_removal)
>>  		 * removed from the slot/adapter.
>>  		 */
>>  		msleep(1000);
>> +
>> +		/* Ignore link or presence changes caused by power off */
>> +		atomic_and(~(PCI_EXP_SLTSTA_DLLSC | PCI_EXP_SLTSTA_PDC),
>> +			   &ctrl->pending_events);
>>  	}
>>  
>>  	/* turn off Green LED */
>> -- 
>> 2.20.1

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