SRPL_RC_INIT(9) FreeBSD Kernel Developer's Manual SRPL_RC_INIT(9)
NAME
srpl_rc_init, SRPL_HEAD, SRPL_ENTRY, SRPL_INIT, SRPL_FIRST, SRPL_NEXT,
SRPL_FOLLOW, SRPL_FOREACH, SRPL_LEAVE, SRPL_RC_INITIALIZER - singly-
linked shared reference pointer list
SYNOPSIS
#include <sys/srp.h>
struct srpl_rc;
void
srpl_rc_init(struct srpl_rc *rc, void (*ref)(void *, void *),
void (*unref)(void *, void *), void *ctx);
SRPL_HEAD(HEADNAME, TYPE);
SRPL_ENTRY(TYPE);
void
SRPL_INIT(SRPL_HEAD *sl);
void *
SRPL_FIRST(struct srp_ref *sr, SRPL_HEAD *sl);
void *
SRPL_NEXT(struct srp_ref *sr, struct TYPE *listelm, FIELDNAME);
void *
SRPL_FOLLOW(struct srp_ref *sr, struct TYPE *listelm, FIELDNAME);
SRPL_FOREACH(VARNAME, struct srp_ref *sr, SRPL_HEAD *sl, FIELDNAME);
void
SRPL_LEAVE(struct srp_ref *sr);
SRPL_RC_INITIALIZER(void (*ref)(void *, void *),
void (*unref)(void *, void *), void *ctx);
DESCRIPTION
The SRPL list macros build a linked list on top of shared reference
pointers. This allows concurrent traversal of a linked list and access
to the items on the list.
SRP lists are a generic type represented by a SRPL_HEAD. The elements
inserted into the list must be structures that contain a SRPL_ENTRY
field. Further, the elements must also support reference counting as
insertion and removal operations can cause items to be temporarily
referenced by multiple SRPs within the list at the same time.
srpl_rc_init() initialises the SRP list refcounts rc structure so it can
be used to manage the reference counts on elements in the list. The
insertion or removal of an element in an SRP list will increment the
reference counts on elements within the list via calls to ref. As these
references are released by the SRP infrastructure, the reference counts
will be decremented by calls to unref. unref is also responsible for
freeing the element when the reference count reaches 0. Both ref and
unref will be called with ctx as their first argument and a pointer to
the element as their second argument.
SRPL_INIT() initialises the SRP list sl to an empty state.
SRPL_FIRST() accesses the first element in the SRP list sl and holds its
reference via sr.
SRPL_NEXT() accesses the element in the SRP list after listelm and holds
its reference via sr.
SRPL_FOLLOW() accesses the element in the SRP list after listelm and
swaps the previous reference held via sr for the reference of the newly
accessed item.
SRPL_FOREACH() creates a loop for traversing the list. Every call to
SRPL_FOREACH() must have a corresponding call to SRPL_LEAVE() to release
references to the list and its elements.
SRPL_LEAVE() releases references to the list and its elements held by
previous calls to SRPL_FIRST(), SRPL_NEXT(), SRPL_FOLLOW(), or
SRPL_FOREACH().
An srpl_rc declaration can be initialised with the SRPL_RC_INITIALIZER()
macro.
CONTEXT
SRPL_INIT(), SRPL_FIRST(), SRPL_NEXT(), SRPL_FOLLOW(), SRPL_FOREACH(),
and SRPL_LEAVE() may be called during autoconf, from process context, or
from interrupt context.
srpl_rc_init(), may be called during autoconf or from process context.
RETURN VALUES
SRPL_FIRST(), SRPL_NEXT(), and SRPL_FOLLOW() return a pointer to elements
in the SRP list, or NULL if there are no more elements.
SEE ALSO
SRPL_FIRST_LOCKED(9)
HISTORY
The srp API was originally written by Jonathan Matthew
<
[email protected]> and David Gwynne <
[email protected]>. The SRP list
API first appeared in OpenBSD 5.9.
FreeBSD 14.1-RELEASE-p8 November 21, 2016 FreeBSD 14.1-RELEASE-p8