Re: [Tarantool-patches] [PATCH luajit] Fix interaction between profiler hooks and finalizers.

[Igor Munkin via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Sergey,

I've checked the patch into all long-term branches in tarantool/luajit
and bumped a new version in master, 2.10 and 1.10.

On 06.06.22, Sergey Kaplun wrote:
> From: Mike Pall <mike>
> 
> Thanks to Julien Desgats.
> 
> (cherry picked from commit 92fa45f9eb5d9aa732c6b972a85c26120d7612b4)
> 
> Embedded LuaJIT profiler uses the following approach:
> * Create trigger on timer signals, which set `HOOK_PROFILE` flag on
>   `g->hookmask` (if not set already) and update all BC instructions
>   dispatch.
> * When any of instruction is executed, callback set by user on profiler
>   initialize is called. After the dispatch table updated again to
>   the old static values, and flags are reset.
> * `HOOK_PROFILE` flag will set again and dispatch will updated at the next
>   tick of the timer.
> 
> Before call to __gc finalizer the old hookmask is saved to be restored
> later. When the second step is happening on call of __gc metamethod
> `HOOK_PROFILE` flag is reset. But right after that the old hook
> disposition (with `HOOK_PROFILE`) is restored, when we leaving
> `gc_call_finalizer()` without updating the dispatch table, so the
> profiler callback is never called again.
> 
> This patch updates dispatch table right after hooks manipulation in
> `gc_call_finalizer()` and prevent ticks influence inside finalizer
> calls.
> 
> Sergey Kaplun:
> * added the description and the test for the problem
> 
> Part of tarantool/tarantool#6548
> ---
> 
> Side note: PR has 2 extra commits because the tarantool/luajit master
> (tarantool branch) isn't bumped in the tarantool yet.
> 
> Branch: https://github.com/tarantool/luajit/tree/skaplun/lj-512-profiler-hook-finalizers-full-ci
> Tarantool PR: https://github.com/tarantool/tarantool/pull/7237
> Related issues:
> * https://github.com/LuaJIT/LuaJIT/issues/512
> * https://github.com/tarantool/tarantool/issues/6548
> 
> 
>  src/lj_gc.c                                   |  2 ++
>  src/lj_obj.h                                  |  3 +-
>  src/lj_profile.c                              |  2 +-
>  .../lj-512-profiler-hook-finalizers.test.lua  | 31 +++++++++++++++++++
>  4 files changed, 36 insertions(+), 2 deletions(-)
>  create mode 100644 test/tarantool-tests/lj-512-profiler-hook-finalizers.test.lua
> 

<snipped>

> -- 
> 2.34.1
> 

-- 
Best regards,
IM