NAME¶
new_unrhdr
,
delete_unrhdr
,
alloc_unr
,
alloc_unr_specific
,
free_unr
—
kernel unit number allocator
SYNOPSIS¶
#include
<sys/systm.h>
struct unrhdr *
new_unrhdr
(
int
low,
int
high,
struct mtx
*mutex);
void
delete_unrhdr
(
struct
unrhdr *uh);
int
alloc_unr
(
struct
unrhdr *uh);
int
alloc_unrl
(
struct
unrhdr *uh);
int
alloc_unr_specific
(
struct
unrhdr *uh,
u_int item);
void
free_unr
(
struct
unrhdr *uh,
u_int item);
DESCRIPTION¶
The kernel unit number allocator is a generic facility, which allows to allocate
unit numbers within a specified range.
new_unrhdr
(low,
high,
mutex)
- Initialize a new unit number allocator entity. The
low and
high arguments specify minimum and
maximum number of unit numbers. There is no cost associated with the range
of unit numbers, so unless the resource really is finite,
INT_MAX
can be used. If
mutex is not
NULL
, it is used for locking when
allocating and freeing units. Otherwise, internal mutex is used.
delete_unrhdr
(uh)
- Destroy specified unit number allocator entity.
alloc_unr
(uh)
- Return a new unit number. The lowest free number is always allocated. This
function does not allocate memory and never sleeps, however it may block
on a mutex. If no free unit numbers are left,
-1
is returned.
alloc_unrl
(uh)
- Same as
alloc_unr
() except that mutex
is assumed to be already locked and thus is not used.
alloc_unr_specific
(uh,
item)
- Allocate a specific unit number. This function allocates memory and thus
may sleep. The allocated unit number is returned on success. If the
specified number is already allocated or out of the range,
-1
is returned.
free_unr
(uh,
item)
- Free a previously allocated unit number. This function may require
allocating memory, and thus it can sleep. There is no pre-locked
variant.
CODE REFERENCES¶
The above functions are implemented in
sys/kern/subr_unit.c.
HISTORY¶
Kernel unit number allocator first appeared in
FreeBSD
6.0.
AUTHORS¶
Kernel unit number allocator was written by
Poul-Henning Kamp. This manpage was written
by
Gleb Smirnoff.