Ubuntu
gccgo-4.9 package

  1. Bug #1304754
  2. Comment #9

Comment 9 for bug 1304754

Revision history for this message
Anton Blanchard (anton-samba) wrote : Re: gccgo on ppc64el using split stacks when not supported

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.