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 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? J. -- Hail Eris. All hail Discordia. | .''`. Debian GNU/Linux Developer Fnord? | : :' : Happy to accept PGP signed | `. `' or encrypted mail - RSA | `- key on the keyservers. -- 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>
