Hi, On Tuesday 10 July 2018 09:17 PM, Greg Kroah-Hartman wrote: > On Tue, Jul 10, 2018 at 05:40:21PM +0200, Rafael J. Wysocki wrote: >> On Tue, Jul 10, 2018 at 2:59 PM, Greg Kroah-Hartman >> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: >>> On Tue, Jul 10, 2018 at 02:51:33PM +0200, Rafael J. Wysocki wrote: >>>> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> >>>> >>>> Commit 52cdbdd49853 (driver core: correct device's shutdown order) >>>> introduced a regression by breaking device shutdown on some systems. >>>> >>>> Namely, the devices_kset_move_last() call in really_probe() added by >>>> that commit is a mistake as it may cause parents to follow children >>>> in the devices_kset list which then causes shutdown to fail. For >>>> example, 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 any more. >>>> >>>> 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 and it only covered an issue >>>> with system shutdown, while system-wide suspend/resume potentially >>>> had the same issue on the affected platforms (which was not covered). >>>> >>>> Moreover, the shutdown issue originally addressed by the change in >>>> really_probe() made by commit 52cdbdd49853 is not present in 4.18-rc >>>> any more, since dra7 started to use the sdhci-omap driver which >>>> doesn't disable any regulators during shutdown, so the really_probe() >>>> part of commit 52cdbdd49853 can be safely reverted. [The original >>>> issue was related to the omap_hsmmc driver used by dra7 previously.] >>>> >>>> For the above reasons, revert the really_probe() modifications made >>>> by commit 52cdbdd49853. >>>> >>>> The other code changes made by commit 52cdbdd49853 are useful and >>>> they need not be reverted. >>>> >>>> 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> >>>> Tested-by: Pingfan Liu <kernelfans@xxxxxxxxx> >>>> Reviewed-by: Kishon Vijay Abraham I <kishon@xxxxxx> >>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> >>>> --- >>>> >>>> -> v2: Added information from Kishon on the fact that it should be safe >>>> to revert the really_probe() modifications added by the >>>> problematic commit. Also added the Reviewed-by tag from Kishon. >>> >>> Looks good to me, want me to queue it up in my tree, or are you going to >>> send it on to Linus? >> >> Please queue it up. >> >>> And shouldn't this have a stable tag as well? >> >> That is sort of a gray area, because I think it may expose the >> shutdown issue on dra7 in -stable, but technically it still fixes a >> regression in the driver core. So your call I suppose. :-) > > Being bug compatible is key :) > > I'll add a stable tag. sure. If I see the issue in dra7, I'll send a stable fix in omap_hsmmmc driver. Thanks Kishon
