MLOCKALL(3C) Standard C Library Functions MLOCKALL(3C)

mlockall, munlockall - lock or unlock address space

#include <sys/mman.h>
int mlockall(int flags);

int munlockall(void);

The mlockall() function locks in memory all pages mapped by an address space.

The value of flags determines whether the pages to be locked are those currently mapped by the address space, those that will be mapped in the future, or both:

       MCL_CURRENT  Lock current mappings
       MCL_FUTURE   Lock future mappings

If MCL_FUTURE is specified for mlockall(), mappings are locked as they are added to the address space (or replace existing mappings), provided sufficient memory is available. Locking in this manner is not persistent across the exec family of functions (see exec(2)).

Mappings locked using mlockall() with any option may be explicitly unlocked with a munlock() call (see mlock(3C)).

The munlockall() function removes address space locks and locks on mappings in the address space.

All conditions and constraints on the use of locked memory that apply to mlock(3C) also apply to mlockall().

Locks established with mlockall() are not inherited by a child process after a fork(2) call, and are not nested.

Upon successful completion, the mlockall() and munlockall() functions return 0. Otherwise, they return −1 and set errno to indicate the error.

The mlockall() and munlockall() functions will fail if:


Some or all of the memory in the address space could not be locked due to sufficient resources. This error condition applies to mlockall() only.


The flags argument contains values other than MCL_CURRENT and MCL_FUTURE.


The {PRIV_PROC_LOCK_MEMORY} privilege is not asserted in the effective set of the calling process.

See attributes(7) for descriptions of the following attributes:

Interface Stability Standard
MT-Level MT-Safe

exec(2), fork(2), memcntl(2), mmap(2), mlock(3C), plock(3C), sysconf(3C), attributes(7), standards(7)

March 22, 2004 OmniOS