Comment 0 for bug 1776887

This upstream bug has been confirmed to affect Ubuntu users[1]. As per the fix commit (below), the most frequent symptom is a crash of Xorg/Xwayland, i.e. killing the entire GUI, when a laptop is woken from system sleep. Frequency of the bug is described as once every few days[2].

[1] E.g. this user confirms the bug & very specific workaround: https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/1760450/comments/11
[2] E.g. this log of crashes: https://bugzilla.redhat.com/show_bug.cgi?id=1553979#c23

This is a bug in blk-core.c. It is not specific to any one hardware driver. Technically the suspend bug is triggered by the SCSI core - which is used by *all SATA devices*.

The commit also includes a test which quickly and reliably proves the existence of a horrifying bug.

I guess you might avoid this bug only if you have root on NVMe. The other way to not hit the Xorg crash is if you don't use all your RAM, so there's no pressure that leads to cold pages of Xorg being swapped. Also, you won't reproduce the Xorg crash if you suspend+resume immediately. (This frustrated my tests at one point, it only triggered after left the system suspended over lunch :).

Fix: "block: do not use interruptible wait anywhere"

in kernel 4.17: https://github.com/torvalds/linux/commit/1dc3039bc87ae7d19a990c3ee71cfd8a9068f428

in kernel 4.16.8: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=linux-4.16.y&id=7859056bc73dea2c3714b00c83b253d4c22bf7b6

lack of fix in 4.15.0-24.26 (ubuntu 18.04): https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/bionic/tree/block/blk-core.c?id=Ubuntu-4.15.0-24.26#n856

I.e., this bug is still present in Ubuntu source package linux-4.15.0-24.26 (and 4.15.0-23.25). I attach hardware details (lspci-vnvn.log) of a system where this bug is known to happen.

Regards
Alan