linux-kernel - Re: Can a driver->probe be called for two devices at the same time (WAS: Re: [PATCH] crypto/ccp: don't disable interrupts while setting up debugfs)

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Message-ID: <d9fd273b-5d48-a005-ac30-c8bc8aa803ab@amd.com>
Date:   Tue, 27 Feb 2018 14:11:24 -0600
From:   Gary R Hook <gary.hook@....com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "Hook, Gary" <ghook@....com>, linux-crypto@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        linux-kernel@...r.kernel.org
Subject: Re: Can a driver->probe be called for two devices at the same time
 (WAS: Re: [PATCH] crypto/ccp: don't disable interrupts while setting up
 debugfs)

On 02/27/2018 01:36 PM, Sebastian Andrzej Siewior wrote:
> On 2018-02-27 19:40:34 [+0100], Greg Kroah-Hartman wrote:
>> On Tue, Feb 27, 2018 at 06:33:14PM +0100, Sebastian Andrzej Siewior wrote:
>>> On 2018-02-27 11:08:56 [-0600], Gary R Hook wrote:
>>>> That issue remains unclear to me: Are probes of PCI devices guaranteed to be
>>>> serialized? Observations on my CCPs says that they occur in order, but I
>>>> don't know for certain that serialization is guaranteed.
>>>>
>>>> Is there a definitive statement on this somewhere that I just don't know
>>>> about?
>>
>> The bus enforces this.
>>
>>> So the question if a driver can probe two devices simultaneously.
>>
>> Depends on the bus type.
> 
> PCI

So the question is whether or not PCI enforces serial activity within a 
domain. The CCPs are all on different buses, so that doesn't matter.

I think we don't care in this situation, given that the CCP driver has 
minor requirements for locking. I just found it an interesting (albeit 
somewhat academic) question.

Thanks,
Gary