[Tarantool-patches] [PATCH] lua: avoid panic if HOOK_GC is not active

[Sergey Kaplun]

Hi, Igor!

Thanks for the review!

On 22.12.20, Igor Munkin wrote:
> Sergey,
> 
> Thanks for the patch! LGTM except a couple of nits below.
> 
> Minor: Strictly saying there is no panic if GC hook is not active
> (literally any Lua code except the finalizers), but panic occurs when
> the active hook is not HOOK_GC. So I propose to tune the commit subject
> the following way:
> | lua: avoid panic if HOOK_GC is not an active hook

Yes, it's better. Thanks!

> 
> On 22.12.20, Sergey Kaplun wrote:
> > Panic at fiber.yield() occures inside any active hook.
> 
> Minor: I rearrange this line a bit, feel free to ignore.
> | Platform panic occurs when fiber.yield() is used within any active
> | (i.e. being executed now) hook.

Look nice for me. Applied :)

> 
> > 
> > This is the regression from 96dbc49d097a96af5273cce2b5663db5917f4ea9
> > ('lua: prohibit fiber yield when GC hook is active').
> > 
> > This patch fixes false positive panic in cases when VM is not running
> > a GC hook.
> > 
> > Reported-by: Michael Filonenko <filonenko.mikhail at gmail.com>
> > Follows up #4727
> 
> Minor: I guess this patch doesn't follow #4727 but rather #4518
> (considering the commit message for the patch you mentioned above). So I
> propose to use either "Relates to #4518" or "Follows up #4518" instead.
> I personally prefer the first one, since it occured #4518 relates to
> totally another issue.
> 

Fixed.

> > Closes #5649
> > ---
> > 
> > Branch: https://github.com/tarantool/tarantool/tree/skaplun/gh-5649-fix-for-debug-hook
> > Issue: https://github.com/tarantool/tarantool/issues/5649
> > CI: https://gitlab.com/tarantool/tarantool/-/pipelines/233249505
> > 
> >  src/lua/utils.c                               |  2 +-
> >  .../gh-5649-yield-in-debug-hook.test.lua      | 25 +++++++++++++++++++

<snipped>

> > +-- Return to second fiber.
> 
> Minor: s/to second/to the second/.

Fixed! Thanks!

> 

<snipped>

> 
> -- 
> Best regards,
> IM

I've updated commit message and comments in code considering your and Igor comments.
Branch is force-pushed.

New commit message is the follows:
| lua: avoid panic if HOOK_GC is not an active hook
|
| Platform panic occurs when fiber.yield() is used within any active
| (i.e. being executed now) hook.
|
| It is a regression caused by 96dbc49d097a96af5273cce2b5663db5917f4ea9
| ('lua: prohibit fiber yield when GC hook is active').
|
| This patch fixes false positive panic in cases when VM is not running
| a GC hook.
|
| Relates to #4518
| Closes #5649
|
| Reported-by: Michael Filonenko <filonenko.mikhail at gmail.com>

-- 
Best regards,
Sergey Kaplun