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

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

The following consistently fails with Thread package 3.0b2 on linux using
tcl 9.0b2 when you run "tclsh9.0 test.tcl"

== test.tcl ==
package require Thread
set pool [::tpool::create -minworkers 1 -maxworkers 4 -idletime 5 -initcmd
[list source somefile.tcl]]
::tpool::post -detached -nowait $pool [list sayhi]
after 10000 [list set v 1]
vwait v

== somefile.tcl ==
package require Thread
proc sayhi {} {
    set fmt {[%d/%b/%Y:%H:%M:%S %z]}
    puts str=[clock format 1722260433 -format $fmt]
}

== Here is the message from the AddressSanitizer ==

/home/phi/build-projects/tcl9.0b2/unix/tclUnixThrd.c:915:12: runtime error:
load of null pointer of type 'pthread_key_t'
AddressSanitizer:DEADLYSIGNAL
=================================================================
==71907==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000
(pc 0x7f27d6a09c7f bp 0x7f27cc225910 sp 0x7f27cc2258f0 T1)
==71907==The signal is caused by a READ memory access.
==71907==Hint: address points to the zero page.
AddressSanitizer:DEADLYSIGNAL
AddressSanitizer: nested bug in the same thread, aborting.

== Here is how I compiled tcl 9.0b2 ==

CFLAGS="-fsanitize=address -fsanitize=undefined -DPURIFY"
LDFLAGS="-fsanitize=address -fsanitize=undefined" ./configure
--enable-symbols=all


On Mon, Jul 29, 2024 at 7:57 AM Neophytos Demetriou <neo...@gm...>
wrote:

> hmm, I disabled all above extensions and it still occurs, which reminded
> me I also use Thread package 3.0b2 and some preliminary investigation seems
> to show that it only happens when Thread package is loaded (3.0b2)
>
> more tomorrow and again sorry for wasting your time
>
> - Neophytos
>
>
> On Mon, Jul 29, 2024 at 7:22 AM Neophytos Demetriou <neo...@gm...>
> wrote:
>
>> 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
>>>
>>> _______________________________________________
>>> Tcl-Core mailing lis...@li...https://lists.sourceforge.net/lists/listinfo/tcl-core
>>>
>>>