linux-kernel - 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: <20180227173314.uko5xpf4od2fn74g@linutronix.de>
Date:   Tue, 27 Feb 2018 18:33:14 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Gary R Hook <gary.hook@....com>
Cc:     "Hook, Gary" <ghook@....com>, linux-crypto@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: 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 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?

So the question if a driver can probe two devices simultaneously. I'm
not sure. We have PROBE_PREFER_ASYNCHRONOUS which defers the probe to
worker. However I have no idea if two of those worker can run at the
same time.

> I think a mutex would be just fine; I got this wrong, clearly. Let me work
> up a patch using a mutex.

I've sent one. Why not just ack it and be done with it?

> Gary

Sebastian