Re: [TCLCORE] PURIFY and unloading extensions issue (?)

[Neophytos D. <neo...@gm...>]

Hi Sergey,

Thanks for your message. Answers below.

did you test it before or after [96910cd8822ffb8f]
> <https://core.tcl-lang.org/tcl/info/96910cd8822ffb8f>? Just to ensure it
> is still acute...
>

It was with tcl 9.0b2, so before that change.


> The whole "unload" thing was initially introduced by Nathan in
> [3b0e92b198b86975] <https://core.tcl-lang.org/tcl/info/3b0e92b198b86975>,
> however it seemed to have some issues (like [34870ab5756911d1]
> <https://core.tcl-lang.org/tcl/info/34870ab5756911d1> or
> [ae09f6b190ceec31] <https://core.tcl-lang.org/tcl/info/ae09f6b190ceec31>),
> which I tried to fix in the last time as good as I was able to do that.
>

I cannot tell if it is relevant or not. It does not look like it.


> Which versions (and platforms) are affected or do you mean exactly here?
> Is it stock tcl or some application of you, that uses Tcl as a subsystem
> (in particular, it is Tcl_Main* or your own main)?
>

It was a tcl file that loaded twebserver in the main thread and twebserver,
tjson and thtml in the spawn twebserver threads. All of these extensions
were using Tcl_CreateThreadExitHandler in their initialization function.
They did not have to but I did not notice that was the case before this
issue. Changing them all to use CreateExitHandler seems to have resolved
the issue.

I will investigate further tomorrow and report back but my guess is that
there is a TCL_TSD_INIT used somewhere when the thread exit handler runs
that causes this issue during unload.

Regards,
Neophytos

PS. My apologies but I have to run right now. I will check further tomorrow
and report back.

Regards,
> Sergey.
>
> 29.07.2024 10:29, Neophytos Demetriou wrote:
>
> Hi,
>
> When the PURIFY flag is used Tcl_Exit calls Tcl_Finalize that in turn
> calls TclFinalizeSynchronization, which sets tsdGlobal.key to NULL via
> TclFinalizeThreadStorage.
>
> Then, when it afterwards tries to unload extensions, it attempts to use
> the TSD (thread-specific data) again and because tsdGlobal.key is NULL, the
> AddressSanitizer complains about a NULL pthread key.
>
> I was not able to track where the TSD is used during unloading or if this
> is an issue with the extensions being used and whether they have to unload
> in a specific way. As a consequence I stopped using the PURIFY flag but if
> anyone has any suggestions, please let us know.
>
> Kind regards,
> Neophytos
>
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