Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH] driver core: Ensure proper suspend/resume ordering | Date | Thu, 17 Sep 2015 02:07:48 +0200 |
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On Wednesday, September 16, 2015 03:27:55 PM Alan Stern wrote: > On Wed, 16 Sep 2015, Grygorii Strashko wrote: > > > I think, It should prohibited to probe devices during suspend/hibernation. > > And solution introduced in this patch might help to fix it - > > in general, we could do : > > - add sync point on suspend enter: wait_for_device_probe() and > > - prohibit probing: move all devices which will request probing into > > deferred_probe list > > - one suspend exit: allow probing and do driver_deferred_probe_trigger > > That could work; it's a good idea. > > > I'd like to mention here that this patch will work only > > if dmp_list will be filled according device creation order ("parent<-child" dependencies) > > *AND* according device's probing order ("supplier<-consumer"). > > So, if there is the case when Parent device can be probed AFTER its children > > - it will not work, because "parent<-child" dependencies will not be tracked > > any more :( Sry, I could not even imagine that such crazy case exist :'( > > If we avoid moving devices to the end of the dpm_list when they already > have children, then we should be okay, right? > > > Are there any other subsystems with the same behavior like PCI? > > I don't know. > > > If not - probably, it could be fixed in PCI subsystem using device_pm_move_after() or > > device_move() in PCIe ports probe. > > if yes - ... maybe we can scan/re-check and reorder dpm_list on suspend enter and > > restore ("parent<-child" dependencies). > > > Truth is that smth. need to be done 100%. Personally, I was hit by this issue also, > > and it cost me 3 hours of debugging and I came up with the same patch as > > Bill Huang, then spent some time trying to understand what is wrong with PCI > > - finally, I've just changed the order of my devices in DT :) > > > > Also, I think, it will be good to have this patch in -next to collect more feedbacks. > > I like the idea of forcing all probes during a sleep transition to be > deferred. We could carry them out just before unfreezing the user > threads. That combined with the change mentioned above ought to be > worth testing.
Agreed.
Thanks, Rafael
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