On Sun, 2024-09-29 at 21:27 +0800, Leon Hwang wrote:
> Previously, I fixed a tailcall infinite loop issue caused by trampoline[0].
>
> At this time, I fix a tailcall infinite loop issue caused by tailcall and
> freplace combination by preventing updating extended prog to prog_array map
> and preventing extending tail callee prog with freplace:
>
> 1. If a prog or its subprog has been extended by freplace prog, the prog
> can not be updated to prog_array map.
> 2. If a prog has been updated to prog_array map, it or its subprog can not
> be extended by freplace prog.
So, once this series is applied we essentially have:
- three variables:
- tgt_prog->aux->is_extended
- tgt_prog->aux->prog_array_member_cnt
- trampoline->extension_prog
- four operations:
- link/attach extension program 'prog' using trampoline 'tr'
- unlink/detach extension program 'prog' using trampoline 'tr'
- put program 'tgt_prog' into prog array
- remove program 'tgt_prog' from prog array
And above four operations have the following pseudo-code with regards
to update of the variables:
- link/attach extension program 'prog' using trampoline 'tr':
with lock(tgt_prog->ext_mutex):
if tgt_prog->aux->prog_array_member_cnt:
return error
if tr->extension_prog:
return error
tr->extension_prog = prog
tgt_prog->is_extended = true
- unlink/detach extension program 'prog' using trampoline 'tr':
with lock(tgt_prog->ext_mutex):
tr->extension_prog = NULL
tgt_prog->is_extended = false
- put program 'tgt_prog' into prog array:
with lock(tgt_prog->ext_mutex):
if tgt_prog->aux->is_extended:
return error
tgt_prog->aux->prog_array_member_cnt++
- remove program 'tgt_prog' from prog array:
with lock(tgt_prog->ext_mutex):
tgt_prog->aux->prog_array_member_cnt--
I think this is correct, would be great if someone with more
concurrency related experience would take a look.
[...]
