mlock(2)

DESCRIPTION

The mlock() system call allows the calling process to lock a segment of the process virtual address space into memory. Any addressable segment of the process' address space may be locked. Locked segments are immune to all routine swapping.

addr must be a valid address in the process virtual address space. addr + len must also be a valid address in the process virtual address space.

Locks are applied at page boundaries that encompass the range from addr to addr + len. If any address within the range is not valid, an error is returned and no locks are applied.

munlock() or munlockall() can be used to unlock memory segments (or all memory segments) locked with mlock().

Regardless of how many times a process locks a page, a single munlock() or munlockall() will unlock it. An munlock() of a page within a range specified in an mlock() call results in only the range specified in the munlock() being unlocked.

When memory is shared by multiple processes and mlocks are applied to the same physical page by multiple processes, a page remains locked until the last lock is removed from that page.

Locks applied with mlock() are not inherited by a child process.

The effective user ID of the calling process must be a superuser or the user must be a member of a group that has the MLOCK privilege (see getprivgrp(2) and setprivgrp(1M))

Although plock() and the mlock() family of functions may be used together in an application, each may affect the other in unexpected ways. This practice is not recommended.

RETURN VALUE

mlock() returns the following values:

ERRORS

If mlock() fails, errno is set to one of the following values:

EXAMPLES

The following call to mlock() locks the first 10 pages of the calling process in memory:

SEE ALSO

setprivgrp(1M), getprivgrp(2), mlockall(2), munlock(2), munlockall(2), plock(2)

STANDARDS CONFORMANCE

mlock(): POSIX Realtime Extensions, IEEE Std 1003.1b