munlock()

Updated: October 26, 2022

Unlock the address space of a process

Synopsis:

#include <sys/mman.h>

int munlock(const void * addr, 
            size_t len);

Arguments:

addr
The starting address for the range of process address space.
len
The amount of memory to unlock, in bytes.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The munlock() function unlocks the whole pages containing any part of the address space of the process starting at address addr and continuing for len bytes, regardless of how many times mlock() has been called by the process for any of the pages in the specified range. The addr must be a multiple of PAGESIZE, which depends on the target platform.

If any of the pages in the range specified to a call to munlock() are also mapped into the address spaces of other processes, any locks established on those pages by another process are unaffected by the call of this process to munlock(). If any of the pages in the range specified by a call to munlock() are also mapped into other portions of the address space of the calling process outside the range specified, any locks established on those pages via the other mappings are also unaffected by this call.

Returns:

0
Success.
-1
An error occurred (errno is set).

Errors:

ENOMEM
Some or all of the address range specified by the addr and len arguments doesn't correspond to valid mapped pages in the address space of the process.

Classification:

POSIX 1003.1 MLR

Safety:  
Cancellation point No
Interrupt handler No
Signal handler Yes
Thread Yes