From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
Ashok Raj <ashok.raj@intel.com>,
Keith Busch <keith.busch@intel.com>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
Lukas Wunner <lukas@wunner.de>,
Michael Jamet <michael.jamet@intel.com>,
Yehezkel Bernat <yehezkel.bernat@intel.com>,
Mario.Limonciello@dell.com, linux-pci@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 8/8] PCI: pciehp: Check that the device is really present before touching it
Date: Mon, 23 Oct 2017 14:04:45 +0300 [thread overview]
Message-ID: <20171023110445.GA29656@lahna.fi.intel.com> (raw)
In-Reply-To: <20171020211502.GR6332@bhelgaas-glaptop.roam.corp.google.com>
On Fri, Oct 20, 2017 at 04:15:02PM -0500, Bjorn Helgaas wrote:
> > +
> > + /* Check if the device is really there anymore */
> > + present = presence ? pci_device_is_present(dev) : false;
> > +
> > + if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE && present) {
> > pci_read_config_byte(dev, PCI_BRIDGE_CONTROL, &bctl);
>
> I don't like this fix because it's still racy. We always have to be deal
> with a config read that returns 0xffffffff, even if we previously checked
> pci_device_is_present(). The device might have disappeared in the interim.
That's a fair point. I guess it is better just to check if bctl holds
0xffff before we decide it is a display device.
I'll rework this patch and send an updated version separately.
next prev parent reply other threads:[~2017-10-23 11:04 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-13 18:35 [PATCH v2 0/8] PCI: Improvements for native PCIe hotplug Mika Westerberg
2017-10-13 18:35 ` [PATCH v2 1/8] PCI: Move pci_hp_add_bridge() to drivers/pci/probe.c Mika Westerberg
2017-10-13 18:35 ` [PATCH v2 2/8] PCI: Open-code the two pass loop when scanning bridges Mika Westerberg
2017-10-13 18:35 ` [PATCH v2 3/8] PCI: Do not allocate more buses than available in parent Mika Westerberg
2017-10-13 18:35 ` [PATCH v2 4/8] PCI: Distribute available buses to hotplug capable bridges Mika Westerberg
2017-10-13 18:35 ` [PATCH v2 5/8] PCI: Distribute available resources " Mika Westerberg
2017-10-13 18:35 ` [PATCH v2 6/8] PCI: pciehp: Fix race condition handling surprise link down Mika Westerberg
2017-10-13 18:35 ` [PATCH v2 7/8] PCI: pciehp: Do not clear Presence Detect Changed during initialization Mika Westerberg
2017-10-13 18:35 ` [PATCH v2 8/8] PCI: pciehp: Check that the device is really present before touching it Mika Westerberg
2017-10-20 21:15 ` Bjorn Helgaas
2017-10-23 11:04 ` Mika Westerberg [this message]
2017-10-20 21:37 ` [PATCH v2 0/8] PCI: Improvements for native PCIe hotplug Bjorn Helgaas
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