linux-kernel - Re: [PATCH RFC v2 2/4] PCI: pciehp: Do not turn off slot if presence comes up after link

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Message-ID: <20190223064926.mh24zzlj4xykwcjf@wunner.de>
Date:   Sat, 23 Feb 2019 07:49:26 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Alex_Gagniuc@...lteam.com
Cc:     mr.nuke.me@...il.com, bhelgaas@...gle.com, Austin.Bolen@...l.com,
        keith.busch@...el.com, Shyam.Iyer@...l.com, okaya@...nel.org,
        linux-pci@...r.kernel.org, gustavo@...eddedor.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v2 2/4] PCI: pciehp: Do not turn off slot if presence
 comes up after link

On Fri, Feb 22, 2019 at 07:56:28PM +0000, Alex_Gagniuc@...lteam.com wrote:
> On 2/21/19 1:36 AM, Lukas Wunner wrote:
> > On Tue, Feb 19, 2019 at 07:20:28PM -0600, Alexandru Gagniuc wrote:
> >>   	mutex_lock(&ctrl->state_lock);
> >> +	present = pciehp_card_present(ctrl);
> >> +	link_active = pciehp_check_link_active(ctrl);
> >>   	switch (ctrl->state) {
> > 
> > These two assignments appear to be superfluous as you're also performing
> > them in pciehp_check_link_active().
> 
> Not sure. Between the first check, and this check, you can have several 
> seconds elapse depending on whether the driver's .probe()/remove() is 
> invoked. Whatever you got at the beginning would be stale. If you had a 
> picture dictionary and looked up 'bad idea', it would have a picture of 
> the above code with the second check removed.

I don't quite follow.  You're no longer using the "present" and
"link_active" variables in pciehp_handle_presence_or_link_change(),
the variables are set again further down in the function and you're
*also* reading PDS and DLLLA in is_delayed_presence_up_event().
So the above-quoted assignments are superfluous.  Am I missing something?

(Sorry, I had copy-pasted the wrong function name, I meant
is_delayed_presence_up_event() above, not pciehp_check_link_active().


> I've got all the other review comments addressed in my local branch. I'm 
> waiting on Lord Helgass' decision on which solution is better.
             ^^^^^^^^^^^^

Can we keep this discussion in a neutral tone please?

Thanks,

Lukas