On Mon, Jul 9, 2018 at 3:57 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: > On Fri, Jul 6, 2018 at 5:01 AM Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote: >> >> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> >> >> The devices_kset_move_last() call in really_probe() is a mistake >> as it may cause parents to follow children in the devices_kset list >> which then causes system shutdown to fail. Namely, if a device has >> children before really_probe() is called for it (which is not >> uncommon), that call will cause it to be reordered after the children >> in the devices_kset list and the ordering of that list will not >> reflect the correct device shutdown order. >> >> Also it causes the devices_kset list to be constantly reordered >> until all drivers have been probed which is totally pointless >> overhead in the majority of cases. >> >> For that reason, revert the really_probe() modifications made by >> commit 52cdbdd49853. > > I'm sure you've considered this, but I can't figure out whether this > patch will reintroduce the problem that was solved by 52cdbdd49853. > That patch updated two places: (1) really_probe(), the change you're > reverting here, and (2) device_move(). > > device_move() is only called from 4-5 places, none of which look > related to the problem fixed by 52cdbdd49853, so it seems like that > problem was probably resolved by the hunk you're reverting. That's right, but I don't want to revert all of it. The other parts of it are kind of useful as they make the handling of the devices_kset list be consistent with the handling of dpm_list. The hunk I'm reverting, however, is completely off. It not only is incorrect (as per the above), but it also causes the devices_kset list and dpm_list to be handled differently. It had attempted to fix something, but it failed miserably at that. >> Fixes: 52cdbdd49853 (driver core: correct device's shutdown order) >> Link: https://lore.kernel.org/lkml/CAFgQCTt7VfqM=UyCnvNFxrSw8Z6cUtAi3HUwR4_xPAc03SgHjQ@xxxxxxxxxxxxxx/ >> Reported-by: Pingfan Liu <kernelfans@xxxxxxxxx> >> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> >> --- >> drivers/base/dd.c | 8 -------- >> 1 file changed, 8 deletions(-) >> >> Index: linux-pm/drivers/base/dd.c >> =================================================================== >> --- linux-pm.orig/drivers/base/dd.c >> +++ linux-pm/drivers/base/dd.c >> @@ -434,14 +434,6 @@ re_probe: >> goto probe_failed; >> } >> >> - /* >> - * Ensure devices are listed in devices_kset in correct order >> - * It's important to move Dev to the end of devices_kset before >> - * calling .probe, because it could be recursive and parent Dev >> - * should always go first >> - */ >> - devices_kset_move_last(dev); >> - >> if (dev->bus->probe) { >> ret = dev->bus->probe(dev); >> if (ret) >>
