linux-kernel - Re: [PATCH v11 23/23] CXL/PCI: Disable CXL protocol error interrupts during CXL Port cleanup

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Message-ID: <aMGUMACDTT5a2-XA@gourry-fedora-PF4VCD3F>
Date: Wed, 10 Sep 2025 11:07:28 -0400
From: Gregory Price <gourry@...rry.net>
To: Terry Bowman <terry.bowman@....com>
Cc: dave@...olabs.net, jonathan.cameron@...wei.com, dave.jiang@...el.com,
	alison.schofield@...el.com, dan.j.williams@...el.com,
	bhelgaas@...gle.com, shiju.jose@...wei.com, ming.li@...omail.com,
	Smita.KoralahalliChannabasappa@....com, rrichter@....com,
	dan.carpenter@...aro.org, PradeepVineshReddy.Kodamati@....com,
	lukas@...ner.de, Benjamin.Cheatham@....com,
	sathyanarayanan.kuppuswamy@...ux.intel.com,
	linux-cxl@...r.kernel.org, alucerop@....com, ira.weiny@...el.com,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v11 23/23] CXL/PCI: Disable CXL protocol error interrupts
 during CXL Port cleanup

Hi Terry,

On Tue, Aug 26, 2025 at 08:35:38PM -0500, Terry Bowman wrote:
> Introduce cxl_mask_proto_interrupts() to call pci_aer_mask_internal_errors().
> Add calls to cxl_mask_proto_interrupts() within CXL Port teardown for CXL
> Root Ports, CXL Downstream Switch Ports, CXL Upstream Switch Ports, and CXL
> Endpoints. Follow the same "bottom-up" approach used during CXL Port
> teardown.
> 
...
> @@ -1471,6 +1475,8 @@ static void cxl_detach_ep(void *data)
>  {
>  	struct cxl_memdev *cxlmd = data;
>  
> +	cxl_mask_proto_interrupts(cxlmd->cxlds->dev);
> +
>  	for (int i = cxlmd->depth - 1; i >= 1; i--) {
>  		struct cxl_port *port, *parent_port;
>  		struct detach_ctx ctx = {

While testing v10 of this patch set, we found ourselves with a deadlock
on boot with the following stack in the hung task:

[  252.784440]  <TASK>
[  252.789090]  schedule+0x5d6/0x1670
[  252.796629]  ? schedule_preempt_disabled+0xa/0x10
[  252.807061]  schedule_preempt_disabled+0xa/0x10
[  252.817108]  __mutex_lock+0x245/0x7b0
[  252.825229]  cxl_mask_proto_interrupts+0x23/0x50
[  252.835470]  cxl_detach_ep+0x25/0x2e0

This occurs on a system which fails to probe ports fully due to the
duplicate id error resolved by the Delayed HB patch set.  

But it's concerning that there's a deadlock condition without that
patch set. Can you help try to eyeball this?  I'm trying to get more
debug info, but testing system availability is limited.

~Gregory