samba - Sep 1998 - SUNOS: Samba grabs all semaphores, breaking other softwares (PR#9755)

Ole.H.Nielsen@fysik.dtu.dk wrote:
> 
> SAMBA grabs ALL available semaphores minus 1 on SunOS 4.1.3,
> where the kernel has 60, see /usr/include/sys/sem.h:
> #define SEMMNS  60              /* # of semaphores in system */
> 
> This is a MAJOR PROBLEM to us, since our backup software
> (IBM ADSM) also needs available semaphores for the client
> part to work.  Hence we can choose between running SAMBA
> or running backups :-(
Hi Ole, nice to hear from you again.
> 
> On AIX 4.2.1 we see just 1 or 2 semaphores taken by SAMBA,
> so this is a SunOS specific problem.  We'd really like to
> get this bug under control...
> 
It's not actually a bug really, more a questionable
design decision.

The solution for Samba 1.9.18pXX is to set the number
of semaphores manually in shmem_sysv.c, ie. change
the lines:

#ifdef SEMMSL
#define SHMEM_HASH_SIZE (SEMMSL-1)
#else
#define SHMEM_HASH_SIZE 63
#endif

to be just :

#define SHMEM_HASH_SIZE <whatever you want here>

Samba-2 won't have this problem as it is much
more conservative about SYSV semaphore use. I'm
CC:ing this reply to the mailing list as I think
people might be interested in this answer.

Cheers,

	Jeremy Allison,
	Samba Team.
-- 
--------------------------------------------------------
Buying an operating system without source is like buying
a self-assembly Space Shuttle with no instructions.
--------------------------------------------------------

-- Jeremy Allison wrote:
> > SAMBA grabs ALL available semaphores minus 1 on SunOS 4.1.3,
> > where the kernel has 60, see /usr/include/sys/sem.h:
> > #define SEMMNS  60              /* # of semaphores in system */
...
> The solution for Samba 1.9.18pXX is to set the number
> of semaphores manually in shmem_sysv.c, ie. change
> the lines:
> 
> #ifdef SEMMSL
> #define SHMEM_HASH_SIZE (SEMMSL-1)
> #else
> #define SHMEM_HASH_SIZE 63
> #endif
> 
> to be just :
> 
> #define SHMEM_HASH_SIZE <whatever you want here>
I added this bit of code after the above lines in shmem_sysv.c:

#ifdef SUNOS4
/* Do not grab all available semaphores (64) on SunOS 4 */
#undef SHMEM_HASH_SIZE
#define SHMEM_HASH_SIZE 10
#endif

Now SAMBA grabs only 11 out of 64 available (by default)
semaphores, and I'm happy again :-)  ADSM backup works 
for us once again, now that there are available semaphores.

Developers:  How about adding this hack to the main 1.9.18 code ?
It's really a problem on SunOS 4.

Best regards,
Ole Holm Nielsen
Department of Physics, Building 307
Technical University of Denmark, DK-2800 Lyngby, Denmark