mlock()

Lock a range of process address space in physical memory

Synopsis:

#include <sys/mman.h>

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

Arguments:

addr
The starting address for the range of process address space.
len
The amount of the memory to lock, in bytes. There's no limit on the amount of memory that a process may lock, other than the amount of physical memory in the system.

Library:

libc

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

Description:

The mlock() function locks a range of process address space starting at address addr and continuing for length len. The addr must be a multiple of PAGESIZE, which depends on the target platform.

Note: The full POSIX implementation for this function was added in the QNX Neutrino Core OS 6.3.2.

In order to lock memory, your process must have the PROCMGR_AID_MEM_LOCK ability enabled. For more information, see procmgr_ability().

The successful call to mlock() function ensures that the pages are memory-resident (i.e., the addresses always reside in physical memory). For more information, see "Locking memory" in the Process Manager chapter of the System Architecture guide.

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.
  • Locking the pages mapped by the specified range would exceed the limit on the amount of memory that the process may lock. In QNX Neutrino, this limit is specified by the RLIMIT_MEMLOCK resource, which you can set with setrlimit().
EAGAIN
Some or all of the memory identified by the operation couldn't be locked when the call was made.
EPERM
The calling process doesn't have the required permission; see procmgr_ability().

Classification:

POSIX 1003.1 MLR

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