Help needed to identify golang fork / memory corruption issue on FreeBSD

[Konstantin Belousov]

On Tue, Mar 28, 2017 at 09:23:24AM +0100, Steven Hartland wrote:
> As I stopped the panic before that I couldn't tell so I've re-run with 
> some debug added just before the panic to capture the addresses of the 
> workbuf structure that the issue was detected in, here goes (parent: 
> 62620, child: 98756):
> 
> workbuf: 0x800b51800
> fatal error: workbuf is not empty
> workbuf: 0x800a72000
> fatal error: workbuf is empty
> workbuf: 0x800a72000
> fatal error: workbuf is not empty
I do not understand.  Why do you show several addresses ?  Wouldn't the
runtime panic after detecting the discrepancy, so there could be only one
address ?

> 
> procstat -v 62620 98756
>    PID              START                END PRT  RES PRES REF SHD FLAG 
> TP PATH
> 62620           0x400000           0x70e000 r-x  309  595 5   1 CN-- vn 
> /root/golang/src/test5/test5
> 62620           0x70e000           0x951000 r--  254  595 5   1 CN-- vn 
> /root/golang/src/test5/test5
> 62620           0x951000           0x988000 rw-   31    0 1   0 C--- vn 
> /root/golang/src/test5/test5
> 62620           0x988000           0x9ab000 rw-   18    0 1   0 C--- df
> 62620        0x800951000        0x8009f1000 rw-   36    0 1   0 C--- df
> 62620        0x8009f1000        0x800ac1000 rw-   28    0 1   0 C--- df
> 62620        0x800ac1000        0x800ad1000 rw-   16    0 1   0 C--- df
> 62620        0x800ad1000        0x800b91000 rw-    5    0 1   0 C--- df
> 62620        0x800b91000        0x800bd1000 rw-    2    0 1   0 C--- df
> 62620        0x800bd1000        0x800c11000 rw-    2    0 1   0 C--- df
> 62620        0x800c11000        0x800c51000 rw-    1    1 2   0 CN-- df
> 62620        0x800c51000        0x800c91000 rw-    1    0 1   0 C--- df
> 62620        0x800c91000        0x800cd1000 rw-    1    0 1   0 C--- df
> 62620       0xc000000000       0xc000001000 rw-    1    1 2   0 CN-- df
> 62620       0xc41fff0000       0xc41fff8000 rw-    3    3 2   0 CN-- df
> 62620       0xc41fff8000       0xc420200000 rw-  251    0 1   0 C--- df
> 62620     0x7ffffffdf000     0x7ffffffff000 rwx    2    0 1   0 C--D df
> 62620     0x7ffffffff000     0x800000000000 r-x    1    1 28   0 ---- ph
> 98756           0x400000           0x70e000 r-x  309  595 5   1 CN-- vn 
> /root/golang/src/test5/test5
> 98756           0x70e000           0x951000 r--  254  595 5   1 CN-- vn 
> /root/golang/src/test5/test5
> 98756           0x951000           0x988000 rw-   31    0 2   1 CN-- vn 
> /root/golang/src/test5/test5
> 98756           0x988000           0x9ab000 rw-   18   18 2   1 CN-- df
> 98756        0x800951000        0x8009f1000 rw-   36   36 2   1 CN-- df
> 98756        0x8009f1000        0x800ac1000 rw-   28   28 2   1 CN-- df
> 98756        0x800ac1000        0x800ad1000 rw-   16   16 2   1 CN-- df
> 98756        0x800ad1000        0x800b91000 rw-    5    5 2   1 CN-- df
> 98756        0x800b91000        0x800bd1000 rw-    2    2 2   1 CN-- df
> 98756        0x800bd1000        0x800c11000 rw-    2    2 2   1 CN-- df
> 98756        0x800c11000        0x800c51000 rw-    1    1 2   0 CN-- df
> 98756        0x800c51000        0x800c91000 rw-    1    1 2   1 CN-- df
> 98756        0x800c91000        0x800cd1000 rw-    1    1 2   1 CN-- df
> 98756       0xc000000000       0xc000001000 rw-    1    1 2   0 CN-- df
> 98756       0xc41fff0000       0xc41fff8000 rw-    3    3 2   0 CN-- df
> 98756       0xc41fff8000       0xc420200000 rw-  251    0 1   0 C--- df
> 98756     0x7ffffffdf000     0x7ffffffff000 rwx    2    2 2   1 CN-D df
> 98756     0x7ffffffff000     0x800000000000 r-x    1    1 28   0 ---- ph
> 
>      Regards
>      Steve