[07:55] <scoopex> i have a problem with a deadlocked kernel driver. in former times (on s390x) i used "crash" to attach a debugger to the kernel and to get a backtrace of the blocked syscall. what can i use in a similar way. i installed "crash" on 16.04 system and it seems to be the thing i am searching for, but i have not managed to attach to the running kernel ("crash /boot/vmlinux-4.10.0-33-generic 
[07:55] <scoopex> /boot/System.map-4.10.0-33-generic") any hints?
[08:13] <smb> scoopex, not sure but you might have more luck by picking the source (package) of crash from zesty and re-compile it for xenial
[08:16] <smb> oh wait... to attach to the running kernel you would not use the files from /boot
[08:25] <smb> scoopex, you need a vmlinuz from a ddeb (http://ddebs.ubuntu.com/pool/main/l/linux/). That is what crash is referring to as namelist. The other argument is optionally a memory dump or (if not given, it will try to attach to /dev/kmem (only works as root)
[08:34] <scoopex> smb: i used https://github.com/torvalds/linux/blob/master/scripts/extract-vmlinux to get a uncompressed kernel image. as i remember it was possible to add a System.map to have the positions of functions available to crash
[08:38] <scoopex> i perfomed a "strace -f -o /tmp/foo crash /boot/vmlinux-4.10.0-33-generic" and there is no access to "kmem" only a failing access to "/dev/crash"
[08:40] <smb> scoopex, normally it is enough to use the (unstripped) vmlinux from the ddeb but newer kernels often add things which crash might not (yet) have catched up with
[08:41] <scoopex> there is no /dev/kmem and not /dev/crash on my system....
[08:51] <smb> it uses /proc/kcore then, but again not sure the xenial crash can handle 4.10 kernels in all situations (kaslr causes a lot of pain)
[09:11] <scoopex> smb: but i also see no attempt in stracte to use or open /proc/kcore
[09:24] <scoopex> hmm, how do you inspect the behavior of kernel threads in a running system? are the alternatives?
[09:25] <scoopex> automated crashdumps of standard kernels would also have the same problem, right?
[09:26] <smb> scoopex, the dump files created by kdump-tools were working from what I remember
[09:27] <scoopex> but "crash" also has a option "--kaslr auto
[09:28] <smb> it has but that does not really seem to work well
[21:59] <kees> sforshee: hi! you around?