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  1. Avoid concurrent calls to bindtextdomain().

  1. BUG #18312: libpq: PQsetdbLogin() not thread-safe

    The Post Office <noreply@postgresql.org> — 2024-01-26T10:06:48Z

    The following bug has been logged on the website:

Bug reference:      18312
Logged by:          Christian Maurer
Email address:      c.maurer@gmx.at
PostgreSQL version: 16.1
Operating system:   Windows 10 Pro
Description:        

Hi

When calling PQsetdbLogin() concurrently the program crashes with RC=3.

Server: PostgreSQL 16.1 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 11.4.1
20230605 (Red Hat 11.4.1-2), 64-bit
libpq: postgresql-16.1-1-windows-x64-binaries.zip (coming from
https://www.enterprisedb.com/download-postgresql-binaries)

Output:
PQisthreadsafe: 1
Connect 0
Connect 2
Connect 1
Connect 3
Connected 0
Connected 2
Finished 0
Finished 2
=> 'End' was not reached
=> %ERRORLEVEL% is 3
=> Thread 1 and 3 did not connect/finish

When calling PQsetdbLogin() and PQfinish() once before the multi-threading
starts, there is no crash and we get the expected output:
PQisthreadsafe: 1
Connect 0
Connect 2
Connect 3
Connect 1
Connected 3
Finished 3
Connected 1
Finished 1
Connected 2
Connected 0
Finished 2
Finished 0
End

Regards
Christian

-- main.cpp start --
#include <iostream>
#include <thread>
#include <vector>
#include <pgsql/libpq-fe.h>

void test(int i)
{
    try {
        std::cout << "Connect " << i << std::endl;
        PGconn *pgConn = PQsetdbLogin("myHost", (const char*)NULL, (const
char*)NULL, (const char*)NULL, "myDatabase", "myUser", "myPassword");
        std::cout << "Connected " << i << std::endl;
        PQfinish(pgConn);
        std::cout << "Finished " << i << std::endl;
    }
    catch (...)
    {
        std::cout << "Exception occurred in " << i << std::endl;
    }
}

int main()
{
    try {
        std::cout << "PQisthreadsafe: " << PQisthreadsafe() << std::endl;

        //PGconn* pgConn = PQsetdbLogin("myHost", (const char*)NULL, (const
char*)NULL, (const char*)NULL, "myDatabase", "myUser", "myPassword");
        //PQfinish(pgConn);

        const std::size_t maxThreads = 4U;
        std::vector<std::thread> myThreads;
        for (std::size_t i = 0; i < maxThreads; ++i)
            myThreads.push_back(std::thread(test, i));

        for (std::thread& myThread : myThreads)
            myThread.join();

        std::cout << "End" << std::endl;
    }
    catch (...)
    {
        std::cout << "Exception occurred in main" << std::endl;
    }

    return 0;
}
-- main.cpp end --

  2. Aw: BUG #18312: libpq: PQsetdbLogin() not thread-safe

    Christian Maurer <c.maurer@gmx.at> — 2024-02-02T10:10:54Z

    <html><head></head><body><div style="font-family: Verdana;font-size: 12.0px;"><div>Hi</div>

<div>&nbsp;</div>

<div>I managed to capture a stack trace for the crash via WinDbg:</div>

<div>&nbsp;</div>

<div>Frame Index&nbsp;&nbsp; &nbsp; &nbsp;Call Site&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Child-SP&nbsp;&nbsp; &nbsp; &nbsp; &nbsp;Return Address<br/>
[0x0] &nbsp; &nbsp; &nbsp; &nbsp; ntdll!NtTerminateProcess+0x14 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0x18aa9fdf88 &nbsp; 0x7fffce3cda98<br/>
[0x1] &nbsp; &nbsp; &nbsp; &nbsp; ntdll!RtlExitUserProcess+0xb8 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0x18aa9fdf90 &nbsp; 0x7fffcd99e82b<br/>
[0x2] &nbsp; &nbsp; &nbsp; &nbsp; KERNEL32!ExitProcessImplementation+0xb &nbsp; 0x18aa9fdfc0 &nbsp; 0x7fffcd42a155<br/>
[0x3] &nbsp; &nbsp; &nbsp; &nbsp; msvcrt!_crtExitProcess+0x15 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0x18aa9fdff0 &nbsp; 0x7fffcd42a7c5<br/>
[0x4] &nbsp; &nbsp; &nbsp; &nbsp; msvcrt!doexit+0x171 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0x18aa9fe020 &nbsp; 0x7fffcd41f26d<br/>
[0x5] &nbsp; &nbsp; &nbsp; &nbsp; msvcrt!abort+0x8d &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0x18aa9fe090 &nbsp; 0x68281886<br/>
[0x6] &nbsp; &nbsp; &nbsp; &nbsp; libintl_9!libintl_bindtextdomain+0x56 &nbsp; &nbsp;0x18aa9fe640 &nbsp; 0x7fff7dcd2e93<br/>
[0x7] &nbsp; &nbsp; &nbsp; &nbsp; LIBPQ!PQenv2encoding+0x1193 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0x18aa9fe670 &nbsp; 0x7fff7dcd2c9e<br/>
[0x8] &nbsp; &nbsp; &nbsp; &nbsp; LIBPQ!PQenv2encoding+0xf9e &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 0x18aa9fe6a0 &nbsp; 0x7fff7dcc9263<br/>
[0x9] &nbsp; &nbsp; &nbsp; &nbsp; LIBPQ!PQpingParams+0x2ea3 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0x18aa9fe6d0 &nbsp; 0x7fff7dcc3dcd<br/>
[0xa] &nbsp; &nbsp; &nbsp; &nbsp; LIBPQ!PQconnectPoll+0x90d &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0x18aa9feb50 &nbsp; 0x7fff7dcc6a1c<br/>
[0xb] &nbsp; &nbsp; &nbsp; &nbsp; LIBPQ!PQpingParams+0x65c &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 0x18aa9ff5c0 &nbsp; 0x7fff7dcc50eb<br/>
[0xc] &nbsp; &nbsp; &nbsp; &nbsp; LIBPQ!PQsetdbLogin+0x19b &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 0x18aa9ff5f0 &nbsp; 0x7ff774798078<br/>
[0xd] &nbsp; &nbsp; &nbsp; &nbsp; _HelloWorld!test+0x98 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0x18aa9ff620 &nbsp; 0x7ff774796f17</div>

<div>&nbsp;</div>

<div>It seems to me, that it is related to&nbsp;BUG #17299</div>

<div>&nbsp;</div>

<div>Regards,</div>

<div>Christian Maurer<br/>
<br/>
<br/>
&nbsp;</div></div></body></html>

  3. Aw: BUG #18312: libpq: PQsetdbLogin() not thread-safe

    Christian Maurer <c.maurer@gmx.at> — 2024-02-02T10:21:46Z

    Hi

(Again. Sorry for the html-formatting in my previous mail.)
 
I managed to capture a stack trace for the crash via WinDbg:
 
Frame Index      Call Site                                   Child-SP        Return Address
[0x0]         ntdll!NtTerminateProcess+0x14            0x18aa9fdf88   0x7fffce3cda98
[0x1]         ntdll!RtlExitUserProcess+0xb8            0x18aa9fdf90   0x7fffcd99e82b
[0x2]         KERNEL32!ExitProcessImplementation+0xb   0x18aa9fdfc0   0x7fffcd42a155
[0x3]         msvcrt!_crtExitProcess+0x15              0x18aa9fdff0   0x7fffcd42a7c5
[0x4]         msvcrt!doexit+0x171                      0x18aa9fe020   0x7fffcd41f26d
[0x5]         msvcrt!abort+0x8d                        0x18aa9fe090   0x68281886
[0x6]         libintl_9!libintl_bindtextdomain+0x56    0x18aa9fe640   0x7fff7dcd2e93
[0x7]         LIBPQ!PQenv2encoding+0x1193              0x18aa9fe670   0x7fff7dcd2c9e
[0x8]         LIBPQ!PQenv2encoding+0xf9e               0x18aa9fe6a0   0x7fff7dcc9263
[0x9]         LIBPQ!PQpingParams+0x2ea3                0x18aa9fe6d0   0x7fff7dcc3dcd
[0xa]         LIBPQ!PQconnectPoll+0x90d                0x18aa9feb50   0x7fff7dcc6a1c
[0xb]         LIBPQ!PQpingParams+0x65c                 0x18aa9ff5c0   0x7fff7dcc50eb
[0xc]         LIBPQ!PQsetdbLogin+0x19b                 0x18aa9ff5f0   0x7ff774798078
[0xd]         _HelloWorld!test+0x98                    0x18aa9ff620   0x7ff774796f17
 
It seems to me, that it is related to BUG #17299
 
Regards,
Christian Maurer

  4. Re: Aw: BUG #18312: libpq: PQsetdbLogin() not thread-safe

    Tom Lane <tgl@sss.pgh.pa.us> — 2024-02-02T15:48:56Z

    Christian Maurer <c.maurer@gmx.at> writes:
> I managed to capture a stack trace for the crash via WinDbg:
>  
> Frame Index      Call Site                                   Child-SP        Return Address
> [0x0]         ntdll!NtTerminateProcess+0x14            0x18aa9fdf88   0x7fffce3cda98
> [0x1]         ntdll!RtlExitUserProcess+0xb8            0x18aa9fdf90   0x7fffcd99e82b
> [0x2]         KERNEL32!ExitProcessImplementation+0xb   0x18aa9fdfc0   0x7fffcd42a155
> [0x3]         msvcrt!_crtExitProcess+0x15              0x18aa9fdff0   0x7fffcd42a7c5
> [0x4]         msvcrt!doexit+0x171                      0x18aa9fe020   0x7fffcd41f26d
> [0x5]         msvcrt!abort+0x8d                        0x18aa9fe090   0x68281886
> [0x6]         libintl_9!libintl_bindtextdomain+0x56    0x18aa9fe640   0x7fff7dcd2e93
> [0x7]         LIBPQ!PQenv2encoding+0x1193              0x18aa9fe670   0x7fff7dcd2c9e

Hm, so it's bindtextdomain() that is aborting.  Back at [1]
I wondered whether we needed to introduce a critical section
to prevent multiple threads from calling that concurrently,
even though its docs allege you shouldn't have to.  Perhaps
it's thread-safe except on Windows?

			regards, tom lane

[1] https://www.postgresql.org/message-id/flat/CAE7q7Eit4Eq2%3Dbxce%3DFm8HAStECjaXUE%3DWBQc-sDDcgJQ7s7eg%40mail.gmail.com

  5. Re: BUG #18312: libpq: PQsetdbLogin() not thread-safe

    Christian Maurer <c.maurer@gmx.at> — 2024-02-02T16:27:24Z

    > I wondered whether we needed to introduce a critical section
> to prevent multiple threads from calling that concurrently,
> even though its docs allege you shouldn't have to. Perhaps
> it's thread-safe except on Windows?
This would explain, why I could not reproduce the error on Red Hat Enterprise Linux.
 
Regards,
Christian Maurer

  6. Re: BUG #18312: libpq: PQsetdbLogin() not thread-safe

    Tom Lane <tgl@sss.pgh.pa.us> — 2024-02-02T18:19:42Z

    Christian Maurer <c.maurer@gmx.at> writes:
>> I wondered whether we needed to introduce a critical section
>> to prevent multiple threads from calling that concurrently,
>> even though its docs allege you shouldn't have to. Perhaps
>> it's thread-safe except on Windows?

> This would explain, why I could not reproduce the error on Red Hat Enterprise Linux.

Are you in a position to try a source-code patch?  The attached
is very quick-and-dirty, but if it resolves your problem then
we could turn it into something respectable.

			regards, tom lane

  7. Re: BUG #18312: libpq: PQsetdbLogin() not thread-safe

    Christian Maurer <c.maurer@gmx.at> — 2024-02-05T12:49:46Z

    Hi Tom Lane,
 
I could apply your patch and compile libpq on Windows 10.
 
The parallel connect issues are gone now
* in the minimal example and
* also in our regression test which showed the issue in the first place.
 
Would it be possible, that the patch you are aiming to make can be included in version 16.2?
 
Regards,
Christian

  8. Re: BUG #18312: libpq: PQsetdbLogin() not thread-safe

    Tom Lane <tgl@sss.pgh.pa.us> — 2024-02-05T15:24:51Z

    Christian Maurer <c.maurer@gmx.at> writes:
> I could apply your patch and compile libpq on Windows 10.
>  
> The parallel connect issues are gone now
> * in the minimal example and
> * also in our regression test which showed the issue in the first place.

Great, thanks for the confirmation.

> Would it be possible, that the patch you are aiming to make can be included in version 16.2?

I'm afraid we're a few days too late for that --- even if I had
a finished patch, the release freeze started two days ago.
It'll be in the May releases, instead.

			regards, tom lane

  9. Re: BUG #18312: libpq: PQsetdbLogin() not thread-safe

    Tom Lane <tgl@sss.pgh.pa.us> — 2024-02-05T20:05:38Z

    I wrote:
> Christian Maurer <c.maurer@gmx.at> writes:
>> Would it be possible, that the patch you are aiming to make can be included in version 16.2?

> I'm afraid we're a few days too late for that --- even if I had
> a finished patch, the release freeze started two days ago.
> It'll be in the May releases, instead.

For the archives' sake --- I've posted a patch for this at [1].

			regards, tom lane

[1] https://www.postgresql.org/message-id/264860.1707163416%40sss.pgh.pa.us