From: Philip Yarra <philip@utiba.com>
Organization: Utiba
Subject: ECPG still having thread problems on Linux
Date: Tue, 24 Jun 2003 18:25:32 +1000
User-Agent: KMail/1.4.3
To: pgsql-interfaces@postgresql.org
MIME-Version: 1.0
Content-Type: Multipart/Mixed;
	boundary="------------Boundary-00=_KQ8ZFDIW96RHEWU2CL8D"
Message-Id: <200306241825.32527.philip@utiba.com>

--------------Boundary-00=_KQ8ZFDIW96RHEWU2CL8D
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

Hi all, it looks like Lee's ECPG (and libpq) thread-safety patches
have been applied, and configure --with-threads is also added. I
have been doing some testing.

On FreeBSD 4.8, the attached sample app runs without a problem.

However, I still encounter a threading problem on Linux (RedHat 7.3).

I have done the following:
1) cvs update
2) ./configure --with-threads && make && su -c "make install"
3) compiled cn.pgc as follows:
        a) ecpg -t cn.pgc
        b) gcc -I/usr/local/pgsql/include -L/usr/local/pgsql/lib \
                -lecpg -lpgtypes -pthread cn.c
4) ./a.out - one thread runs to completion (inserts 5 records),
        the other hangs (manages one insert, then blocks forever)

Using gdb, I attached to the thread that has locked up, and the backtrace
looks like this:

(gdb) backtrace
#0  0x420e0187 in poll () from /lib/i686/libc.so.6
#1  0x4007d8cc in pqSocketPoll () from /usr/local/pgsql/lib/libpq.so.3
#2  0x4007d7ed in pqSocketCheck () from /usr/local/pgsql/lib/libpq.so.3
#3  0x4007d71f in pqWaitTimed () from /usr/local/pgsql/lib/libpq.so.3
#4  0x4007d6f5 in pqWait () from /usr/local/pgsql/lib/libpq.so.3
#5  0x4007bb53 in PQgetResult () from /usr/local/pgsql/lib/libpq.so.3
#6  0x4007bcbb in PQexec () from /usr/local/pgsql/lib/libpq.so.3
#7  0x40026d81 in ECPGexecute () from /usr/local/pgsql/lib/libecpg.so.4
#8  0x4002724c in ECPGdo () from /usr/local/pgsql/lib/libecpg.so.4
#9  0x08048927 in ins2 ()
#10 0x40043faf in pthread_start_thread () from /lib/i686/libpthread.so.0

Can anyone shed some light on why the behaviour differs between these two=
=20
platforms?=20

Also, perhaps someone other there with access to a different Linux setup=20
(maybe a more recent build than RedHat 7.3, or a different distro) could tr=
y=20
this app themselves to help verify if this is something that's stuffed on=
=20
that release. I think I can rule out this problem being a quirk of my=20
particular setup, as 3 different machines (all running RH7.3) give identica=
l=20
results.

Build env:
Linux 2.4.18-3
gcc version 2.96 20000731 (Red Hat Linux 7.3 2.96-113)

Regards, Philip Yarra.


--------------Boundary-00=_KQ8ZFDIW96RHEWU2CL8D
Content-Type: text/x-csrc;
  charset="us-ascii";
  name="cn.pgc"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="cn.pgc"

/* on linux, you can compile with:
ecpg cn.pgc&& gcc -I/usr/local/pgsql/include -L/usr/local/pgsql/lib -lpgtypes -lecpg -lpthread cn.c

and you'll need this table:

CREATE TABLE foo (
    message character(40)
);

*/


#include <pthread.h>

int main();
void ins1();
void ins2();

int main()
{
	pthread_t thread1, thread2;
	pthread_create(&thread1, NULL, (void *) ins1, NULL);
	pthread_create(&thread2, NULL, (void *) ins2, NULL);
	pthread_join(thread1, NULL);
	pthread_join(thread2, NULL);
	printf("Done!");
	return 0;
}

void ins1()
{
	int i;
	EXEC SQL BEGIN DECLARE SECTION;
	char* cs = "test@host";
	char* bar = "one!";
	EXEC SQL END DECLARE SECTION;
	EXEC SQL WHENEVER sqlerror sqlprint;
	EXEC SQL CONNECT TO :cs AS test1;
	EXEC SQL SET AUTOCOMMIT TO ON;
	for (i = 0; i < 5; i++)
	{
		printf("thread1 inserting\n");
		EXEC SQL INSERT INTO foo VALUES(:bar);
		printf("==>thread1 insert done\n");
	}
	EXEC SQL DISCONNECT test1;
	printf("done!\n");
}


void ins2()
{
	int i;
	EXEC SQL BEGIN DECLARE SECTION;
	char* cs = "test@host";
	char* bar = "two!";
	EXEC SQL END DECLARE SECTION;
	EXEC SQL WHENEVER sqlerror sqlprint;
	EXEC SQL CONNECT TO :cs AS test2;
	EXEC SQL SET AUTOCOMMIT TO ON;
	for (i = 0; i < 5; i++)
	{
		printf("thread2 inserting\n");
		EXEC SQL INSERT INTO foo VALUES(:bar);
		printf("==>thread2 insert done\n");
	}
	EXEC SQL DISCONNECT test2;
	printf("done!\n");
}


--------------Boundary-00=_KQ8ZFDIW96RHEWU2CL8D--