linux-kernel - Re: [PATCH v2 7/7] dmaengine: idxd: Refactor remove call with idxd

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Message-ID: <5dfdb75c-e532-4a5e-8098-7650c6494d78@linux.alibaba.com>
Date: Wed, 19 Feb 2025 21:28:16 +0800
From: Shuai Xue <xueshuai@...ux.alibaba.com>
To: Fenghua Yu <fenghuay@...dia.com>, vinicius.gomes@...el.com,
 dave.jiang@...el.com, vkoul@...nel.org
Cc: nikhil.rao@...el.com, dmaengine@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 7/7] dmaengine: idxd: Refactor remove call with
 idxd_cleanup() helper



在 2025/2/19 05:01, Fenghua Yu 写道:
> Hi, Shuai,
> 
> On 2/14/25 21:44, Shuai Xue wrote:
>> The idxd_cleanup() helper clean up perfmon, interrupts, internals and so
> 
> s/clean/cleans/
> 
> 
>> on. Refactor remove call with idxd_cleanup() helper to avoid code
> s/idxd_cleanup()/the idxd_cleanup()/
>> duplication. Note, this also fixes the missing put_device() for idxd
>> groups, enginces and wqs.
>>
>> Fixes: bfe1d56091c1 ("dmaengine: idxd: Init and probe for Intel data accelerators")
>> Suggested-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
>> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>
>> ---
>>   drivers/dma/idxd/init.c | 13 ++-----------
>>   1 file changed, 2 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
>> index f40f1c44a302..0fbfbe024c29 100644
>> --- a/drivers/dma/idxd/init.c
>> +++ b/drivers/dma/idxd/init.c
>> @@ -1282,20 +1282,11 @@ static void idxd_remove(struct pci_dev *pdev)
>>       get_device(idxd_confdev(idxd));
> get_device() is called here.
>>       device_unregister(idxd_confdev(idxd));
>>       idxd_shutdown(pdev);
>> -    if (device_pasid_enabled(idxd))
>> -        idxd_disable_system_pasid(idxd);
>>       idxd_device_remove_debugfs(idxd);
>> -
>> -    irq_entry = idxd_get_ie(idxd, 0);
>> -    free_irq(irq_entry->vector, irq_entry);
>> -    pci_free_irq_vectors(pdev);
>> +    idxd_cleanup(idxd);
>>       pci_iounmap(pdev, idxd->reg_base);
>> -    if (device_user_pasid_enabled(idxd))
>> -        idxd_disable_sva(pdev);
>> -    pci_disable_device(pdev);
>> -    destroy_workqueue(idxd->wq);
>> -    perfmon_pmu_remove(idxd);
>>       idxd_free(idxd);
> 
> put_device() is called inside idxd_free(). Seems not easy to read code to match the pair.

IMHO, idxd_free() is paired with idxd_alloc() which grap a reference count by
device_initialize(). So, we should match that right pair.

> * When ->release() is called for the idxd->conf_dev, it frees all the memory related
> * to the idxd context.

I did not figure out why you explictly grab reference count of
idxd_confdev(idxd).

idxd_unregister_devices() is paired with idxd_register_devices(), it only
decrease reference through wqs, engines, and groups. So a refcnt of
idxd->conf_dev is still hold by idxd_alloc().

Please correct me, if I missed anything.

> 
> Plus idxd_free() is called only in non FLR case.
> 
> Maybe it's better to change this code to:
> 
> 1. call put_device() outside idxd_free() so that it's easy to match the get_device() and put_deivce in the same level of function.

See my comments above.
> 
> 2. idxd_free() called here is OK because this is not in FLR handler. But only call it in non FLR path in idxd_pci_probe_alloc()
> 

Exactly, so, shoud I add a protection in idxd_free() in a fact that non FLR case will not call it.

Thanks.
Shuai