linux-kernel - Re: [PATCH v2 2/2] PCI: pciehp: Prevent deadlock on disconnect

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Message-ID: <20190819085620.GM19908@lahna.fi.intel.com>
Date:   Mon, 19 Aug 2019 11:56:20 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Sinan Kaya <okaya@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Lukas Wunner <lukas@...ner.de>,
        Keith Busch <keith.busch@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Frederick Lawler <fred@...dlawl.com>,
        "Gustavo A . R . Silva" <gustavo@...eddedor.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] PCI: pciehp: Prevent deadlock on disconnect

On Sun, Aug 18, 2019 at 10:28:13PM -0400, Sinan Kaya wrote:
> On 8/12/2019 10:31 AM, Mika Westerberg wrote:
> > +int pciehp_card_present_or_link_active(struct controller *ctrl)
> >  {
> > -	return pciehp_card_present(ctrl) || pciehp_check_link_active(ctrl);
> > +	int ret;
> > +
> > +	ret = pciehp_card_present(ctrl);
> > +	if (ret)
> > +		return ret;
> > +
> > +	return pciehp_check_link_active(ctrl);
> 
> The semantics of this function changed here. Before it was checking for
> either presence detect bit or link active bit. Now, it is looking to
> have both set.

Hmm, maybe I haven't got enough coffee yet but I'm not sure I understand :)
The intention was that the above two are equivalent with the exception
of handling the possible error.

> There are PCI controllers that won't report presence detect correctly,
> but still report link active.

If that's the case then pciehp_card_present() returns false so we call
pciehp_check_link_active() which should work with those controllers.

What I'm missing here?