From: Bjorn Helgaas <helgaas@kernel.org>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Robert Święcki" <robert@swiecki.net>,
linux-i2c <linux-i2c@vger.kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Linux PCI" <linux-pci@vger.kernel.org>,
"Linux PM" <linux-pm@vger.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>
Subject: Re: [PATCH] pci: Don't call resume callback for nearly bound devices
Date: Tue, 9 Nov 2021 12:12:24 -0600 [thread overview]
Message-ID: <20211109181224.GA1162053@bhelgaas> (raw)
In-Reply-To: <CAJZ5v0hEKO-RFBzkBU+orcM68shODd-qjiuxaYGxhvh2b=NDXA@mail.gmail.com>
On Tue, Nov 09, 2021 at 06:18:18PM +0100, Rafael J. Wysocki wrote:
> On Tue, Nov 9, 2021 at 7:59 AM Uwe Kleine-König
> <u.kleine-koenig@pengutronix.de> wrote:
> > On Mon, Nov 08, 2021 at 08:56:19PM -0600, Bjorn Helgaas wrote:
> > > [+cc Greg: new device_is_bound() use]
> >
> > ack, that's what I would have suggested now, too.
> >
> > > On Mon, Nov 08, 2021 at 10:22:26PM +0100, Uwe Kleine-König wrote:
> > > > pci_pm_runtime_resume() exits early when the device to resume isn't
> > > > bound yet:
> > > >
> > > > if (!to_pci_driver(dev->driver))
> > > > return 0;
> > > >
> > > > This however isn't true when the device currently probes and
> > > > local_pci_probe() calls pm_runtime_get_sync() because then the driver
> > > > core already setup dev->driver. As a result the driver's resume callback
> > > > is called before the driver's probe function is called and so more often
> > > > than not required driver data isn't setup yet.
> > > >
> > > > So replace the check for the device being unbound by a check that only
> > > > becomes true after .probe() succeeded.
> > >
> > > I like the fact that this patch is short and simple.
> > >
> > > But there are 30+ users of to_pci_driver(). This patch asserts that
> > > *one* of them, pci_pm_runtime_resume(), is special and needs to test
> > > device_is_bound() instead of using to_pci_driver().
> >
> > Maybe for the other locations using device_is_bound(&pdev->dev) instead
> > of to_pci_driver(pdev) != NULL would be nice, too?
> >
> > I have another doubt: device_is_bound() should (according to its
> > kernel-doc) be called with the device lock held. For the call stack that
> > is (maybe) fixed here, the lock is held (by __device_attach). We
> > probably should check if the lock is also held for the other calls of
> > pci_pm_runtime_resume().
> >
> > Hmm, the device lock is a mutex, the pm functions might be called in
> > atomic context, right?
> >
> > > It's special because the current PM implementation calls it via
> > > pm_runtime_get_sync() before the driver's .probe() method. That
> > > connection is a little bit obscure and fragile. What if the PM
> > > implementation changes?
> >
> > Maybe a saver bet would be to not use pm_runtime_get_sync() in
> > local_pci_probe()?
>
> Yes, in principle it might be replaced with pm_runtime_get_noresume().
>
> In theory, that may be problematic if a device is put into a low-power
> state on remove and then the driver is bound again to it.
>
> > I wonder if the same problem exists on remove, i.e. pci_device_remove()
> > calls pm_runtime_put_sync() after the driver's .remove() callback was
> > called.
>
> If it is called after ->remove() and before clearing the device's
> driver pointer, then yes.
Yes, that is the case:
pci_device_remove
if (drv->remove) {
pm_runtime_get_sync
drv->remove() # <-- driver ->remove() method
pm_runtime_put_noidle
}
...
pm_runtime_put_sync # <-- after ->remove()
So pm_runtime_put_sync() is called after drv->remove(), and it may
call drv->pm->runtime_idle(). I think the driver may not expect this.
> If this is turned into pm_runtime_put_noidle(), all should work.
pci_device_remove() already calls pm_runtime_put_noidle() immediately
after calling the driver ->remove() method.
Are you saying we should do this, which means pci_device_remove()
would call pm_runtime_put_noidle() twice?
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 1d98c974381c..79c1a920fdc8 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -318,7 +318,7 @@ static long local_pci_probe(void *_ddi)
* count, in its probe routine and pm_runtime_get_noresume() in
* its remove routine.
*/
- pm_runtime_get_sync(dev);
+ pm_runtime_get_noresume(dev);
rc = pci_drv->probe(pci_dev, ddi->id);
if (!rc)
return rc;
@@ -465,7 +465,7 @@ static void pci_device_remove(struct device *dev)
pci_iov_remove(pci_dev);
/* Undo the runtime PM settings in local_pci_probe() */
- pm_runtime_put_sync(dev);
+ pm_runtime_put_noidle(dev);
/*
* If the device is still on, set the power state as "unknown",
next prev parent reply other threads:[~2021-11-09 18:12 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAP145phj7jEy6tkdFMdW-rzPprMTUckaaSrtrVysE-u+S+=Lcg@mail.gmail.com>
2021-11-08 18:58 ` Crashes in 5.15-git in i2c code Bjorn Helgaas
2021-11-08 19:09 ` Bjorn Helgaas
2021-11-08 21:22 ` [PATCH] pci: Don't call resume callback for nearly bound devices Uwe Kleine-König
2021-11-08 21:36 ` Robert Święcki
2021-11-09 0:00 ` Krzysztof Wilczyński
2021-11-09 2:56 ` Bjorn Helgaas
2021-11-09 6:42 ` Greg Kroah-Hartman
2021-11-09 6:59 ` Uwe Kleine-König
2021-11-09 12:42 ` Robert Święcki
2021-11-10 21:26 ` Bjorn Helgaas
2021-11-10 22:01 ` Robert Święcki
2021-11-09 17:18 ` Rafael J. Wysocki
2021-11-09 18:12 ` Bjorn Helgaas [this message]
2021-11-09 18:52 ` Rafael J. Wysocki
2021-11-09 18:58 ` Rafael J. Wysocki
2021-11-09 20:05 ` Bjorn Helgaas
2021-11-09 20:43 ` Uwe Kleine-König
2021-11-10 14:14 ` Bjorn Helgaas
2021-11-10 16:33 ` Robert Święcki
2021-11-10 16:48 ` Rafael J. Wysocki
2021-11-10 17:59 ` Bjorn Helgaas
2021-11-10 21:19 ` Bjorn Helgaas
2021-11-11 17:01 ` Bjorn Helgaas
2021-11-11 17:32 ` Robert Święcki
2021-11-11 18:09 ` Bjorn Helgaas
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20211109181224.GA1162053@bhelgaas \
--to=helgaas@kernel.org \
--cc=bhelgaas@google.com \
--cc=gregkh@linuxfoundation.org \
--cc=linux-i2c@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=rafael@kernel.org \
--cc=robert@swiecki.net \
--cc=u.kleine-koenig@pengutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).