From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Lukas Wunner <lukas@wunner.de>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>,
Bjorn Helgaas <bhelgaas@google.com>,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
Keith Busch <keith.busch@intel.com>,
Alex Williamson <alex.williamson@redhat.com>,
Alexandru Gagniuc <mr.nuke.me@gmail.com>
Subject: Re: [PATCH] PCI/PME: Fix race on PME polling
Date: Tue, 18 Jun 2019 00:43:35 +0200 [thread overview]
Message-ID: <1943367.SoULSMlgxK@kreacher> (raw)
In-Reply-To: <20190617145348.cqmtuqlvabgpo2ky@wunner.de>
On Monday, June 17, 2019 4:53:48 PM CEST Lukas Wunner wrote:
> On Mon, Jun 17, 2019 at 05:35:10PM +0300, Mika Westerberg wrote:
> > Today when doing some PM testing I noticed that this patch actually
> > reveals an issue in our native PME handling. Problem is in
> > pcie_pme_handle_request() where we first convert req_id to struct
> > pci_dev and then call pci_check_pme_status() for it. Now, when a device
> > triggers wake the link is first brought up and then the PME is sent to
> > root complex with req_id matching the originating device. However, if
> > there are PCIe ports in the middle they may still be in D3 which means
> > that pci_check_pme_status() returns 0xffff for the device below so there
> > are lots of
> >
> > Spurious native interrupt"
> >
> > messages in the dmesg but the actual PME is never handled.
> >
> > It has been working because pci_check_pme_status() returned true in case
> > of 0xffff as well and we went and runtime resumed to originating device.
> >
> > I think the correct way to handle this is actually drop the call to
> > pci_check_pme_status() in pcie_pme_handle_request() because the whole
> > idea of req_id in PME message is to allow the root complex and SW to
> > identify the device without need to poll for the PME status bit.
>
> Either that or the call to pci_check_pme_status() should be encapsulated
> in a pci_config_pm_runtime_get() / _put() pair.
And the whole hierarchy might as well be resumed, which could be rather
wasteful.
The problem is that the $subject patch should affect polling only, but it has
side effects beyond that.
next prev parent reply other threads:[~2019-06-17 22:43 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-09 11:29 [PATCH] PCI/PME: Fix race on PME polling Lukas Wunner
2019-06-17 10:37 ` Rafael J. Wysocki
2019-06-17 14:35 ` Mika Westerberg
2019-06-17 14:53 ` Lukas Wunner
2019-06-17 22:43 ` Rafael J. Wysocki [this message]
2019-06-17 22:41 ` Rafael J. Wysocki
2019-06-18 9:45 ` Mika Westerberg
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