linux-kernel - Re: [PATCH] cxl/memdev: fix deadlock in cxl_memdev

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Message-ID: <c8623ed8-04ac-4921-adb0-14cf630a063e@intel.com>
Date: Tue, 10 Feb 2026 16:20:35 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Gregory Price <gourry@...rry.net>, Ira Weiny <ira.weiny@...el.com>
Cc: linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
 kernel-team@...a.com, dave@...olabs.net, jonathan.cameron@...wei.com,
 alison.schofield@...el.com, vishal.l.verma@...el.com,
 dan.j.williams@...el.com
Subject: Re: [PATCH] cxl/memdev: fix deadlock in cxl_memdev_autoremove() on
 attach failure



On 2/10/26 3:46 PM, Gregory Price wrote:
> On Tue, Feb 10, 2026 at 01:44:06PM -0600, Ira Weiny wrote:
>> Gregory Price wrote:
>>>
>>> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
>>> index af3d0cc65138..c0de767b24fb 100644
>>> --- a/drivers/cxl/core/memdev.c
>>> +++ b/drivers/cxl/core/memdev.c
>>> @@ -1098,19 +1098,22 @@ static struct cxl_memdev *cxl_memdev_autoremove(struct cxl_memdev *cxlmd)
>>>  	 * return. Note that failure here could be the result of a race to
>>>  	 * teardown the CXL port topology. I.e. cxl_mem_probe() could have
>>>  	 * succeeded and then cxl_mem unbound before the lock is acquired.
>>> +	 *
>>> +	 * Check under device_lock but unregister outside of it, as
>>> +	 * cxl_memdev_unregister() will also take the device lock.
>>>  	 */
>>> -	guard(device)(&cxlmd->dev);
>>> -	if (cxlmd->attach && !cxlmd->dev.driver) {
>>> -		cxl_memdev_unregister(cxlmd);
>>> -		return ERR_PTR(-ENXIO);
>>> +	scoped_guard(device, &cxlmd->dev) {
>>> +		if (cxlmd->attach && !cxlmd->dev.driver)
>>> +			break;
>>> +
>>> +		rc = devm_add_action_or_reset(cxlmd->cxlds->dev,
>>> +					      cxl_memdev_unregister, cxlmd);
>>
>> This kind of threw me...  Won't this deadlock if
>> devm_add_action_or_reset() fails as well?
>>
>> Need to use devm_add_action() and drop out of the guard on failure.
>>
> 
> lol i pointed out that this patch was a claude recommendation on the
> initial report - didn't look to hard because it fixed this specific
> deadlock with:
> 
> 	if (cxlmd->attach && !cxlmd->dev.driver)
> 		break;
> 
> so yeah, easy enough to fixup.
> 
> I can either v2 or Dave if you want to just make the oneline change
> before pull let me know

With Dan's comments, may as we spin v2. We have time until rc1 releases.

> 
> ~Gregory