Hello, 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()? 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. > Maybe we just need a comment there about why it looks different than > the other PM interfaces? A comment is a good idea for sure. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ |
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