On Wed, Jan 03, 2018 at 11:11:29AM +0900, Joonsoo Kim wrote: > On Tue, Jan 02, 2018 at 11:25:01AM +0100, Rafael J. Wysocki wrote: > > On Tue, Jan 2, 2018 at 3:54 AM, Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote: > > > On Fri, Dec 29, 2017 at 04:36:59PM +0000, Jonathan McDowell wrote: > > >> On Fri, Dec 22, 2017 at 09:21:09AM +0900, Joonsoo Kim wrote: > > >> > On Fri, Dec 08, 2017 at 03:11:59PM +0000, Jonathan McDowell wrote: > > >> > > I've been sitting on this for a while and should have spent time to > > >> > > investigate sooner, but it's been an odd failure mode that wasn't quite > > >> > > obvious. > > >> > > > > >> > > In 4.9 if I cold power on my laptop (Dell E7240) it fails to boot - I > > >> > > don't see anything after grub says its booting. In 4.10 onwards the > > >> > > laptop boots, but I get an Oops as part of the boot and ACPI is unhappy > > >> > > (no suspend, no clean poweroff, no ACPI buttons). The Oops is below; > > >> > > taken from 4.12 as that's the most recent error dmesg I have saved but > > >> > > also seen back in 4.10. It's always address 0x30 for the dereference. > > >> > > > > >> > > Rebooting the laptop does not lead to these problems; it's *only* from a > > >> > > complete cold boot that they arise (which didn't help me in terms of > > >> > > being able to reliably bisect). Once I realised that I was able to > > >> > > bisect, but it leads me to an odd commit: > > >> > > > > >> > > 86d9f48534e800e4d62cdc1b5aaf539f4c1d47d6 > > >> > > (mm/slab: fix kmemcg cache creation delayed issue) > > >> > > > > >> > > If I revert this then I can cold boot without problems. > > >> > > > > >> > > Also I don't see the problem with a stock Debian kernel, I think because > > >> > > the ACPI support is modularised. > > >> > > > >> > Sorry for late response. I was on a long vacation. > > >> > > >> No problem. I've been trying to get around to diagnosing this for a > > >> while now anyway and this isn't a great time of year for fast responses. > > >> > > >> > I have tried to solve the problem however I don't find any clue yet. > > >> > > > >> > >From my analysis, oops report shows that 'struct sock *ssk' passed to > > >> > netlink_broadcast_filtered() is NULL. It means that some of > > >> > netlink_kernel_create() returns NULL. Maybe, it is due to slab > > >> > allocation failure. Could you check it by inserting some log on that > > >> > part? The issue cannot be reproducible in my side so I need your help. > > >> > > >> I've added some debug in acpi_bus_generate_netlink_event + > > >> genlmsg_multicast and the problem seems to be that genlmsg_multicast is > > >> getting called when init_net.genl_sock has not yet been initialised, > > >> leading to the NULL deference. > > >> > > >> Full dmesg output from a cold 4.14.8 boot at: > > >> > > >> https://the.earth.li/~noodles/acpi-problem/dmesg-4.14.8-broken > > >> > > >> And the same kernel after a reboot ("shutdown -r now"): > > >> > > >> https://the.earth.li/~noodles/acpi-problem/dmesg-4.14.8-working > > >> > > >> Patch that I've applied is at > > >> > > >> https://the.earth.li/~noodles/acpi-problem/debug-acpi.diff > > >> > > > > > > Thanks for testing! It's very helpful. > > > > > >> The interesting difference seems to be: > > >> > > >> PCI: Using ACPI for IRQ routing > > >> +ACPI: Generating event type 208 (:9DBB5994-A997-11DA-B012-B622A1EF5492) > > >> +ERROR: init_net.genl_sock is NULL > > >> +BUG: unable to handle kernel NULL pointer dereference at 0000000000000030 > > >> +IP: netlink_broadcast_filtered+0x20/0x3d0 > > >> +PGD 0 P4D 0 > > >> +Oops: 0000 [#1] SMP > > >> +Modules linked in: > > >> +CPU: 0 PID: 29 Comm: kworker/0:1 Not tainted 4.14.8+ #1 > > >> +Hardware name: Dell Inc. Latitude E7240/07RPNV, BIOS A22 10/18/2017 > > >> +Workqueue: kacpi_notify acpi_os_execute_deferred > > >> > > >> 9DBB5994-A997-11DA-B012-B622A1EF5492 is the Dell WMI event GUID and > > >> there's no visible event for it on a reboot, just on a cold power on. > > >> Some sort of ordering issues such that genl_sock is being initialised > > >> later with the slab change? > > > > > > I have checked that there is an ordering issue. > > > > > > genl_init() which initializes init_net->genl_sock is called on > > > subsys_initcall(). > > > > > > acpi_wmi_init() which schedules acpi_wmi_notify_handler() to the > > > workqueue is called on subsys_initcall(), too. > > > (acpi_wmi_notify_handler() -> acpi_bus_generate_netlink_event() -> > > > netlink_broadcast()) > > > > > > In my system, acpi_wmi_init() is called before the genl_init(). > > > Therefore, if the worker is scheduled before genl_init() is done, NULL > > > derefence would happen. > > > > Does it help to change the subsys_initcall() in wmi.c to subsys_initcall_sync()? > > I guess that it would work. I cannot reproduce the issue so it needs > to be checked by Jonathan. Jonathan, could you check the problem > is disappeared with above change? I have confirmed that the problem also occurs when using SLUB instead of SLAB, and that switching drivers/platform/x86/wmi.c to use subsys_initcall_sync() instead of subsys_initcall() fixes the problem for both. Weirdly I don't see the ACPI 208 event at boot time being raised once that patch is in place. J. -- ] https://www.earth.li/~noodles/ [] Synonym: word used when you can't [ ] PGP/GPG Key @ the.earth.li [] spell the one you want [ ] via keyserver, web or email. [] [ ] RSA: 4096/0x94FA372B2DA8B985 [] [ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
