Thread: Need help woth thread support in ecpglib
Hi,
I recently got the following bug report. It appears to be a bug in
pthread implementation in ecpglib/connect.c where
pthread_getspecific(actual_connection_key);
doesn't return the value of actual_connection, the variable used for
non-threaded mode. Problem is I never really used threading in my apps
and didn't do the threading patches. Maybe someone with more knowledge
than me could have a look at this. Thanks.
Michael
---
When using postgresql 8.0 compiled with --enable-thread-safety, new threads
no longer see the default ecpg connection. That was not the case in 7.4.x
compiled with or without --enable-thread-safety.
TEST CASE
The program at the end of this mail sets up a database table named
"dbthreadtest" in the default database. It then spawns 5 threads which each
do a select from that table using the default connection.
If the program is saved as dbthreadtest.pgc, compile with:
ecpg -t -o dbthreadtest.c dbthreadtest.pgc
gcc -Wall -o dbthreadtest dbthreadtest.c -lecpg -lpthread
Results under 7.4.x / 8.0 without --enable-thread-safety:
got id = 1
got id = 1
got id = 1
got id = 1
got id = 1
Results under 8.0 with --enable-thread-safety:
'No such connection NULL in line 76.', sqlcode = -220 select id
TEST PROGRAM
/* -*-C-*- */
#include <stdlib.h>
#include <pthread.h>
#define CHECK_SQL(fmt, args...) \
do \
{ \ if (sqlca.sqlcode != ECPG_NO_ERROR) \ { \
fprintf(stderr, "'%s', sqlcode = %ld " fmt "\n", \ sqlca.sqlerrm.sqlerrmc, \ sqlca.sqlcode,
##args); \ exit (1); \ } \}
\
while (0)
#define FATAL(fmt, args...) \
do \
{ \ fprintf (stderr, fmt "\n", ## args); \ exit (1); \
} \
while (0)
pthread_mutex_t global_lock;
pthread_t global_threads[5];
void
setup_db ()
{ exec sql begin declare section; const char *_user; exec sql end declare section;
pthread_mutex_lock (&global_lock);
_user = getenv ("LOGNAME");
exec sql connect to :_user; CHECK_SQL ("connect");
exec sql create table dbthreadtest (id int); CHECK_SQL ("create dbthreadtest");
exec sql insert into dbthreadtest (id) values (1); CHECK_SQL ("insert 1");
pthread_mutex_unlock (&global_lock);
}
void
teardown_db ()
{ pthread_mutex_lock (&global_lock);
exec sql drop table dbthreadtest; CHECK_SQL ("drop dbthreadtest");
exec sql disconnect; CHECK_SQL ("disconnect");
pthread_mutex_unlock (&global_lock);
}
void *query_db (void *ignorep)
{ exec sql begin declare section; int _id; exec sql end declare section;
pthread_mutex_lock (&global_lock); exec sql select id into :_id from dbthreadtest; CHECK_SQL ("select id");
fprintf (stdout, "got id = %d\n", _id); pthread_mutex_unlock (&global_lock);
return NULL;
}
int
main ()
{ int i;
pthread_mutex_init (&global_lock, NULL); setup_db ();
for (i = 0; i < sizeof (global_threads) / sizeof (global_threads[0]);
++i) { if (pthread_create (&global_threads[i], NULL, query_db, NULL))FATAL ("pthread_create %d failed", i); }
for (i = 0; i < sizeof (global_threads) / sizeof (global_threads[0]);
++i) { if (pthread_join (global_threads[i], NULL))FATAL ("pthread_join %d failed", i); }
teardown_db (); return 0;
}
----- End forwarded message -----
--
Michael Meskes
Email: Michael at Fam-Meskes dot De, Michael at Meskes dot (De|Com|Net|Org)
ICQ: 179140304, AIM/Yahoo: michaelmeskes, Jabber: meskes@jabber.org
Go SF 49ers! Go Rhein Fire! Use Debian GNU/Linux! Use PostgreSQL!
Hi Michael, I'll have a look at it this afternoon, unless Lee wants first go.
Regards, Philip.
On Tuesday 12 April 2005 00:28, Michael Meskes wrote:
> Hi,
>
> I recently got the following bug report. It appears to be a bug in
> pthread implementation in ecpglib/connect.c where
>
> pthread_getspecific(actual_connection_key);
>
> doesn't return the value of actual_connection, the variable used for
> non-threaded mode. Problem is I never really used threading in my apps
> and didn't do the threading patches. Maybe someone with more knowledge
> than me could have a look at this. Thanks.
>
> Michael
>
> ---
>
> When using postgresql 8.0 compiled with --enable-thread-safety, new threads
> no longer see the default ecpg connection. That was not the case in 7.4.x
> compiled with or without --enable-thread-safety.
>
> TEST CASE
>
> The program at the end of this mail sets up a database table named
> "dbthreadtest" in the default database. It then spawns 5 threads which each
> do a select from that table using the default connection.
>
> If the program is saved as dbthreadtest.pgc, compile with:
>
> ecpg -t -o dbthreadtest.c dbthreadtest.pgc
> gcc -Wall -o dbthreadtest dbthreadtest.c -lecpg -lpthread
>
> Results under 7.4.x / 8.0 without --enable-thread-safety:
>
> got id = 1
> got id = 1
> got id = 1
> got id = 1
> got id = 1
>
> Results under 8.0 with --enable-thread-safety:
>
> 'No such connection NULL in line 76.', sqlcode = -220 select id
>
> TEST PROGRAM
>
> /* -*-C-*- */
>
> #include <stdlib.h>
> #include <pthread.h>
>
> #define CHECK_SQL(fmt, args...) \
> do \
> { \
> if (sqlca.sqlcode != ECPG_NO_ERROR) \
> { \
> fprintf (stderr, "'%s', sqlcode = %ld " fmt "\n", \
> sqlca.sqlerrm.sqlerrmc, \
> sqlca.sqlcode, ## args); \
> exit (1); \
> } \
> } \
> while (0)
>
> #define FATAL(fmt, args...) \
> do \
> { \
> fprintf (stderr, fmt "\n", ## args); \
> exit (1); \
> } \
> while (0)
>
> pthread_mutex_t global_lock;
> pthread_t global_threads[5];
>
> void
> setup_db ()
> {
> exec sql begin declare section;
> const char *_user;
> exec sql end declare section;
>
> pthread_mutex_lock (&global_lock);
>
> _user = getenv ("LOGNAME");
>
> exec sql connect to :_user;
> CHECK_SQL ("connect");
>
> exec sql create table dbthreadtest (id int);
> CHECK_SQL ("create dbthreadtest");
>
> exec sql insert into dbthreadtest (id) values (1);
> CHECK_SQL ("insert 1");
>
> pthread_mutex_unlock (&global_lock);
> }
>
> void
> teardown_db ()
> {
> pthread_mutex_lock (&global_lock);
>
> exec sql drop table dbthreadtest;
> CHECK_SQL ("drop dbthreadtest");
>
> exec sql disconnect;
> CHECK_SQL ("disconnect");
>
> pthread_mutex_unlock (&global_lock);
> }
>
> void *query_db (void *ignorep)
> {
> exec sql begin declare section;
> int _id;
> exec sql end declare section;
>
> pthread_mutex_lock (&global_lock);
> exec sql select id into :_id from dbthreadtest;
> CHECK_SQL ("select id");
>
> fprintf (stdout, "got id = %d\n", _id);
> pthread_mutex_unlock (&global_lock);
>
> return NULL;
> }
>
> int
> main ()
> {
> int i;
>
> pthread_mutex_init (&global_lock, NULL);
>
> setup_db ();
>
> for (i = 0; i < sizeof (global_threads) / sizeof (global_threads[0]);
> ++i)
> {
> if (pthread_create (&global_threads[i], NULL, query_db, NULL))
> FATAL ("pthread_create %d failed", i);
> }
>
> for (i = 0; i < sizeof (global_threads) / sizeof (global_threads[0]);
> ++i)
> {
> if (pthread_join (global_threads[i], NULL))
> FATAL ("pthread_join %d failed", i);
> }
>
> teardown_db ();
>
> return 0;
> }
>
> ----- End forwarded message -----
>
> --
> Michael Meskes
> Email: Michael at Fam-Meskes dot De, Michael at Meskes dot (De|Com|Net|Org)
> ICQ: 179140304, AIM/Yahoo: michaelmeskes, Jabber: meskes@jabber.org
> Go SF 49ers! Go Rhein Fire! Use Debian GNU/Linux! Use PostgreSQL!
>
> ---------------------------(end of broadcast)---------------------------
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