Horton

Thread

  1. RE: [HACKERS] backend freezeing on win32 fixed (I hope ;-) )

    Horak Daniel <horak@mmp.plzen-city.cz> — 1999-08-17T12:06:26Z

    > In any case, when one backend quits and another one is 
> started, the new
> one will re-use the semaphore no longer used by the defunct backend.

I have tested my solution a bit more and I have to say that reusing a
semaphore by a new backend works OK. But it is not possible for a newly
created backend to use a semaphore allocated by postmaster (it freezes on
test if the semaphore with given key already exists - done with
semId=semget(semKey, 0, 0) in function IpcSemaphoreCreate() in
storage/ipc/ipc.c ). Why it is, I don't know, but it seems that my solution
uses the ipc library in the right way. There are no longer any error
messages from the ipc library when running the server. And I can't say that
the ipc library is a 100% correct implementation of SysV IPC, it is probably
(sure ;-) )caused by the Windows internals.

			Dan

  2. Re: [HACKERS] backend freezeing on win32 fixed (I hope ;-) )

    Bruce Momjian <maillist@candle.pha.pa.us> — 1999-08-17T14:41:28Z

    [Charset iso-8859-1 unsupported, filtering to ASCII...]
> > In any case, when one backend quits and another one is 
> > started, the new
> > one will re-use the semaphore no longer used by the defunct backend.
> 
> I have tested my solution a bit more and I have to say that reusing a
> semaphore by a new backend works OK. But it is not possible for a newly
> created backend to use a semaphore allocated by postmaster (it freezes on
> test if the semaphore with given key already exists - done with
> semId=semget(semKey, 0, 0) in function IpcSemaphoreCreate() in
> storage/ipc/ipc.c ). Why it is, I don't know, but it seems that my solution
> uses the ipc library in the right way. There are no longer any error
> messages from the ipc library when running the server. And I can't say that
> the ipc library is a 100% correct implementation of SysV IPC, it is probably
> (sure ;-) )caused by the Windows internals.

Seems we may have to use the patch, or make some other patch for NT-only
that works around this NT bug.

-- 
  Bruce Momjian                        |  http://www.op.net/~candle
  maillist@candle.pha.pa.us            |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

  3. RE: [HACKERS] backend freezeing on win32 fixed (I hope ;-) )

    Hiroshi Inoue <inoue@tpf.co.jp> — 1999-08-17T23:45:28Z

    > -----Original Message-----
> From: owner-pgsql-hackers@postgreSQL.org
> [mailto:owner-pgsql-hackers@postgreSQL.org]On Behalf Of Horak Daniel
> Sent: Tuesday, August 17, 1999 9:06 PM
> To: 'Tom Lane'
> Cc: 'pgsql-hackers@postgreSQL.org'
> Subject: RE: [HACKERS] backend freezeing on win32 fixed (I hope ;-) )
>
>
> > In any case, when one backend quits and another one is
> > started, the new
> > one will re-use the semaphore no longer used by the defunct backend.
>
> I have tested my solution a bit more and I have to say that reusing a
> semaphore by a new backend works OK. But it is not possible for a newly
> created backend to use a semaphore allocated by postmaster (it freezes on
> test if the semaphore with given key already exists - done with
> semId=semget(semKey, 0, 0) in function IpcSemaphoreCreate() in
> storage/ipc/ipc.c ). Why it is, I don't know, but it seems that
> my solution
> uses the ipc library in the right way. There are no longer any error
> messages from the ipc library when running the server. And I
> can't say that
> the ipc library is a 100% correct implementation of SysV IPC, it
> is probably
> (sure ;-) )caused by the Windows internals.
>

Yutaka Tanida [yutaka@marin.or.jp] and I have examined IPC
library.

We found that postmaster doesn't call exec() after fork() since v6.4.

The value of static/extern variables which cygipc library holds may
be different from their initial values when postmaster fork()s child
backend processes.

I made the following patch for cygipc library on trial.
This patch was effective for Yutaka's test case.

Regards.

Hiroshi Inoue
Inoue@tpf.co.jp

*** sem.c.orig	Tue Dec 01 00:16:25 1998
--- sem.c	Tue Aug 17 13:22:06 1999
***************
*** 58,63 ****
--- 58,78 ----
  static int		  GFirstSem	 = 0;		/*PCPC*/
  static int		  GFdSem	    ;		/*PCPC*/

+ static pid_t	GProcessId = 0;
+
+ static void	init_globals(void)
+ {
+ 	pid_t pid;
+
+ 	if (pid=getpid(), pid != GProcessId)
+ 	{
+ 		GFirstSem = 0;
+ 		used_sems = used_semids = max_semid = 0;
+ 		sem_seq = 0;
+ 		GProcessId = pid;
+ 	}
+ }
+
  /************************************************************************/
  /* Demande d'acces a la zone partagee de gestion des semaphores		*/
  /************************************************************************/
***************
*** 77,82 ****
--- 92,98 ----
  {
      int LRet ;

+ 	init_globals();
      if( GFirstSem == 0 )
      {
  	if( IsGSemSemExist() )
*** shm.c.orig	Tue Dec 01 01:04:57 1998
--- shm.c	Tue Aug 17 13:22:27 1999
***************
*** 59,64 ****
--- 59,81 ----
  static int		  GFirstShm	 = 0;		/*PCPC*/
  static int		  GFdShm	    ;		/*PCPC*/

+ /*****************************************/
+ /*	Initialization of static variables   */
+ /*****************************************/
+ static pid_t GProcessId = 0;
+ static void init_globals(void)
+ {
+ 	pid_t pid;
+
+ 	if (pid=getpid(), pid != GProcessId)
+ 	{
+ 		GFirstShm = 0;
+ 		shm_rss = shm_swp = max_shmid = 0;
+ 		shm_seq = 0;
+ 		GProcessId = pid;
+ 	}
+ }
+
  /************************************************************************/
  /* Demande d'acces a la zone partagee de gestion des shm		*/
  /************************************************************************/
***************
*** 82,87 ****
--- 99,105 ----
  {
   int LRet ;

+  init_globals();
   if( GFirstShm == 0 )
   {
    if( IsGSemShmExist() )
*** msg.c.orig	Tue Dec 01 00:16:09 1998
--- msg.c	Tue Aug 17 13:20:04 1999
***************
*** 57,62 ****
--- 57,77 ----
  static int		  GFirstMsg	 = 0;		/*PCPC*/
  static int		  GFdMsg	    ;		/*PCPC*/

+ /*****************************************/
+ /*	Initialization of static variables   */
+ /*****************************************/
+ static pid_t GProcessId = 0;
+ static void init_globals(void)
+ {
+ 	pid_t pid;
+
+ 	if (pid=getpid(), pid != GProcessId)
+ 	{
+ 		GFirstMsg = 0;
+ 		msgbytes = msghdrs = msg_seq = used_queues = max_msqid = 0;
+ 		GProcessId = pid;
+ 	}
+ }
  /************************************************************************/
  /* Demande d'acces a la zone partagee de gestion des semaphores		*/
  /************************************************************************/
***************
*** 79,84 ****
--- 94,100 ----
  {
   int LRet ;

+  init_globals();
   if( GFirstMsg == 0 )
   {
    if( IsGSemMsgExist() )

  4. Re: [HACKERS] backend freezeing on win32 fixed (I hope ;-) )

    Bruce Momjian <maillist@candle.pha.pa.us> — 1999-09-27T18:32:34Z

    I have added this to the end of the README.NT file.



[Charset iso-8859-1 unsupported, filtering to ASCII...]
> > -----Original Message-----
> > From: owner-pgsql-hackers@postgreSQL.org
> > [mailto:owner-pgsql-hackers@postgreSQL.org]On Behalf Of Horak Daniel
> > Sent: Tuesday, August 17, 1999 9:06 PM
> > To: 'Tom Lane'
> > Cc: 'pgsql-hackers@postgreSQL.org'
> > Subject: RE: [HACKERS] backend freezeing on win32 fixed (I hope ;-) )
> >
> >
> > > In any case, when one backend quits and another one is
> > > started, the new
> > > one will re-use the semaphore no longer used by the defunct backend.
> >
> > I have tested my solution a bit more and I have to say that reusing a
> > semaphore by a new backend works OK. But it is not possible for a newly
> > created backend to use a semaphore allocated by postmaster (it freezes on
> > test if the semaphore with given key already exists - done with
> > semId=semget(semKey, 0, 0) in function IpcSemaphoreCreate() in
> > storage/ipc/ipc.c ). Why it is, I don't know, but it seems that
> > my solution
> > uses the ipc library in the right way. There are no longer any error
> > messages from the ipc library when running the server. And I
> > can't say that
> > the ipc library is a 100% correct implementation of SysV IPC, it
> > is probably
> > (sure ;-) )caused by the Windows internals.
> >
> 
> Yutaka Tanida [yutaka@marin.or.jp] and I have examined IPC
> library.
> 
> We found that postmaster doesn't call exec() after fork() since v6.4.
> 
> The value of static/extern variables which cygipc library holds may
> be different from their initial values when postmaster fork()s child
> backend processes.
> 
> I made the following patch for cygipc library on trial.
> This patch was effective for Yutaka's test case.
> 
> Regards.
> 
> Hiroshi Inoue
> Inoue@tpf.co.jp
> 
> *** sem.c.orig	Tue Dec 01 00:16:25 1998
> --- sem.c	Tue Aug 17 13:22:06 1999
> ***************
> *** 58,63 ****
> --- 58,78 ----
>   static int		  GFirstSem	 = 0;		/*PCPC*/
>   static int		  GFdSem	    ;		/*PCPC*/
> 
> + static pid_t	GProcessId = 0;
> +
> + static void	init_globals(void)
> + {
> + 	pid_t pid;
> +
> + 	if (pid=getpid(), pid != GProcessId)
> + 	{
> + 		GFirstSem = 0;
> + 		used_sems = used_semids = max_semid = 0;
> + 		sem_seq = 0;
> + 		GProcessId = pid;
> + 	}
> + }
> +
>   /************************************************************************/
>   /* Demande d'acces a la zone partagee de gestion des semaphores		*/
>   /************************************************************************/
> ***************
> *** 77,82 ****
> --- 92,98 ----
>   {
>       int LRet ;
> 
> + 	init_globals();
>       if( GFirstSem == 0 )
>       {
>   	if( IsGSemSemExist() )
> *** shm.c.orig	Tue Dec 01 01:04:57 1998
> --- shm.c	Tue Aug 17 13:22:27 1999
> ***************
> *** 59,64 ****
> --- 59,81 ----
>   static int		  GFirstShm	 = 0;		/*PCPC*/
>   static int		  GFdShm	    ;		/*PCPC*/
> 
> + /*****************************************/
> + /*	Initialization of static variables   */
> + /*****************************************/
> + static pid_t GProcessId = 0;
> + static void init_globals(void)
> + {
> + 	pid_t pid;
> +
> + 	if (pid=getpid(), pid != GProcessId)
> + 	{
> + 		GFirstShm = 0;
> + 		shm_rss = shm_swp = max_shmid = 0;
> + 		shm_seq = 0;
> + 		GProcessId = pid;
> + 	}
> + }
> +
>   /************************************************************************/
>   /* Demande d'acces a la zone partagee de gestion des shm		*/
>   /************************************************************************/
> ***************
> *** 82,87 ****
> --- 99,105 ----
>   {
>    int LRet ;
> 
> +  init_globals();
>    if( GFirstShm == 0 )
>    {
>     if( IsGSemShmExist() )
> *** msg.c.orig	Tue Dec 01 00:16:09 1998
> --- msg.c	Tue Aug 17 13:20:04 1999
> ***************
> *** 57,62 ****
> --- 57,77 ----
>   static int		  GFirstMsg	 = 0;		/*PCPC*/
>   static int		  GFdMsg	    ;		/*PCPC*/
> 
> + /*****************************************/
> + /*	Initialization of static variables   */
> + /*****************************************/
> + static pid_t GProcessId = 0;
> + static void init_globals(void)
> + {
> + 	pid_t pid;
> +
> + 	if (pid=getpid(), pid != GProcessId)
> + 	{
> + 		GFirstMsg = 0;
> + 		msgbytes = msghdrs = msg_seq = used_queues = max_msqid = 0;
> + 		GProcessId = pid;
> + 	}
> + }
>   /************************************************************************/
>   /* Demande d'acces a la zone partagee de gestion des semaphores		*/
>   /************************************************************************/
> ***************
> *** 79,84 ****
> --- 94,100 ----
>   {
>    int LRet ;
> 
> +  init_globals();
>    if( GFirstMsg == 0 )
>    {
>     if( IsGSemMsgExist() )
> 
> 
> 


-- 
  Bruce Momjian                        |  http://www.op.net/~candle
  maillist@candle.pha.pa.us            |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026