scoopexi 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?07:55
smbscoopex, not sure but you might have more luck by picking the source (package) of crash from zesty and re-compile it for xenial08:13
smboh wait... to attach to the running kernel you would not use the files from /boot08:16
smbscoopex, 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)08:25
scoopexsmb: 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 crash08:34
scoopexi 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"08:38
smbscoopex, 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 with08:40
scoopexthere is no /dev/kmem and not /dev/crash on my system....08:41
smbit 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)08:51
scoopexsmb: but i also see no attempt in stracte to use or open /proc/kcore09:11
scoopexhmm, how do you inspect the behavior of kernel threads in a running system? are the alternatives?09:24
scoopexautomated crashdumps of standard kernels would also have the same problem, right?09:25
smbscoopex, the dump files created by kdump-tools were working from what I remember09:26
scoopexbut "crash" also has a option "--kaslr auto09:27
smbit has but that does not really seem to work well09:28
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keessforshee: hi! you around?21:59

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