On Wed, Apr 16, 2014 at 4:26 PM, Anton Blanchard <an...@samba.org> wrote: > I've made some progress with these fails. A lot of the confusion is > around the way gccgo hooks the SEGV handler and attempts to backtrace > all goroutines (the code is in runtime_tracebackothers()) > > It does this by calling runtime_gogo() which temporarily switches to the > goroutine using setcontext(). If the context is bad in any way, this > will cause us to SEGV again. I printed out the stack pointer (r1) and > the NIA during this stack backtracing, and we see where things go south > just as we are about to dump goroutine 0: > > goroutine 0 [idle]: > DEBUG: runtime_gogo r1 0 nia 0 > > r1 = 0, nia = 0. When we call setcontext on this invalid context we die > with: > > jujud[5258]: bad frame in setup_rt_frame: 0000000000000000 nip > 0000000000000000 lr 0000000000000000 > > Perhaps we aren't saving away the context for goroutine 0 correctly.
Hmm, could be. It looks like the process was crashing anyway. > > -- > You received this bug notification because you are subscribed to the bug > report. > https://bugs.launchpad.net/bugs/1304754 > > Title: > gccgo on ppc64el using split stacks when not supported > > Status in “gccgo-4.9” package in Ubuntu: > Confirmed > > Bug description: > On kernels 3.13-18 and 3.13-23 (there may be others) the kernel is > killing gccgo compiled binaries > > [18519.444748] jujud[19277]: bad frame in setup_rt_frame: > 0000000000000000 nip 0000000000000000 lr 0000000000000000 > [18519.673632] init: juju-agent-ubuntu-local main process (19220) > killed by SEGV signal > [18519.673651] init: juju-agent-ubuntu-local main process ended, respawning > > In powerpc/kernel/signal_64.c: > > sys_rt_sigreturn is jumping to the badframe: label and executing an > unconditional force_sigsegv which is delivered to the userland > process. Like C++, gccgo tries to decode SIGSEGV as a nil pointer > access and blame some random function that happened to be the top > stack frame. > > Reverting to the 3.13-08 kernel appears to resolve the issue which > (weakly) points the finger at the recent switch to 64k pages. > > To manage notifications about this bug go to: > https://bugs.launchpad.net/ubuntu/+source/gccgo-4.9/+bug/1304754/+subscriptions -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1304754 Title: gccgo on ppc64el using split stacks when not supported To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gccgo-4.9/+bug/1304754/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
