Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCHv3 3/4] drivers/base: clean up the usage of devices_kset_move_last() | Date | Wed, 04 Jul 2018 12:17:06 +0200 |
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On Wednesday, July 4, 2018 6:40:09 AM CEST Pingfan Liu wrote: > On Tue, Jul 3, 2018 at 10:28 PM Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > > > > On Tuesday, July 3, 2018 8:50:41 AM CEST Pingfan Liu wrote: > > > Clean up the referring to the code in commit 52cdbdd49853 ("driver core: > > > correct device's shutdown order"). So later we can revert it safely. > > > > > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > > Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > Cc: Grygorii Strashko <grygorii.strashko@ti.com> > > > Cc: Christoph Hellwig <hch@infradead.org> > > > Cc: Bjorn Helgaas <helgaas@kernel.org> > > > Cc: Dave Young <dyoung@redhat.com> > > > Cc: linux-pci@vger.kernel.org > > > Cc: linuxppc-dev@lists.ozlabs.org > > > Signed-off-by: Pingfan Liu <kernelfans@gmail.com> > > > --- > > > drivers/base/core.c | 7 ------- > > > 1 file changed, 7 deletions(-) > > > > > > diff --git a/drivers/base/core.c b/drivers/base/core.c > > > index 684b994..db3deb8 100644 > > > --- a/drivers/base/core.c > > > +++ b/drivers/base/core.c > > > @@ -127,13 +127,6 @@ static int device_reorder_to_tail(struct device *dev, void *not_used) > > > { > > > struct device_link *link; > > > > > > - /* > > > - * Devices that have not been registered yet will be put to the ends > > > - * of the lists during the registration, so skip them here. > > > - */ > > > - if (device_is_registered(dev)) > > > - devices_kset_move_last(dev); > > > - > > > if (device_pm_initialized(dev)) > > > device_pm_move_last(dev); > > > > You can't do this. > > > > If you do it, that will break power management in some situations. > > > Could you shed light on it? I had a quick browsing of pm code, but it > is a big function, and I got lost in it. > If the above code causes failure, then does it imply that the seq in > devices_kset should be the same as dpm_list?
Generally, yes it should.
> But in device_shutdown(), it only intersect with pm by > pm_runtime_get_noresume(dev) and pm_runtime_barrier(dev). How do these > function affect the seq in dpm_list?
They are not related to dpm_list directly.
However, if you shut down a supplier device before its consumer and that involves power management, then the consumer shutdown may fail and lock up the system
I asked you elsewhere to clearly describe the problem you are trying to address. Please do that in the first place.
Thanks, Rafael
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