SUNOS: Samba grabs all semaphores, breaking other softwares (PR#9755)

[Jeremy Allison]

Ole.H.Nielsen at 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.
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