47.10. Semaphore Limits

Most UNIX implementations impose various limits on the operation of System V semaphores. The following is a list of the Linux semaphore limits. The system call affected by the limit and the error that results if the limit is reached are noted in parentheses.

SEMAEM

This is the maximum value that can be recorded in a semadj total. SEMAEM is defined to have the same value as SEMVMX (described below). (semop(), ERANGE)

SEMMNI

This is a system-wide limit on the number of semaphore identifiers (in other words, semaphore sets) that can be created. (semget(), ENOSPC)

SEMMSL

This is the maximum number of semaphores that can be allocated in a semaphore set. (semget(), EINVAL)

SEMMNS

This is a system-wide limit on the number of semaphores in all semaphore sets. The number of semaphores on the system is also limited by SEMMNI and SEMMSL; in fact, the default value for SEMMNS is the product of the defaults for these two limits. (semget(), ENOSPC)

SEMOPM

This is the maximum number of operations per semop() call. (semop(), E2BIG)

SEMVMX

This is the maximum value for a semaphore. (semop(), ERANGE)