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.Dd September 2, 2012
.Dt CK_EPOCH_CALL 3
.Sh NAME
.Nm ck_epoch_call
.Nd defer function execution until a grace period
.Sh LIBRARY
Concurrency Kit (libck, \-lck)
.Sh SYNOPSIS
.In ck_epoch.h
typedef struct ck_epoch_entry ck_epoch_entry_t;
.br
typedef void ck_epoch_cb_t(ck_epoch_entry_t *);
.Ft void
.Fn ck_epoch_call "ck_epoch_t *epoch" "ck_epoch_record_t *record" "ck_epoch_entry_t *entry" "ck_epoch_cb_t *function"
.Sh DESCRIPTION
The
.Fn ck_epoch_call 3
function will defer the execution of the function pointed to by
.Fa function
until a grace-period has been detected in
.Fa epoch .
The function will be provided
the pointer specified by 
.Fa entry .
The function will execute at some time in the future via calls to
.Fn ck_epoch_reclaim 3 ,
.Fn ck_epoch_barrier 3
or
.Fn ck_epoch_poll 3 .
.Sh EXAMPLE
.Bd -literal -offset indent

#include <ck_epoch.h>
#include <ck_stack.h>
#include <stdlib.h>

/*
 * epoch was previously initialized with ck_epoch_init.
 */
ck_epoch_t *epoch;

struct object {
	int value;
	ck_epoch_entry_t epoch_entry;
};
static struct object *global;

CK_EPOCH_CONTAINER(struct object, epoch_entry, object_container)

void
destroy_object(ck_epoch_entry_t *e)
{
	struct object *o = object_container(e);

	free(o);
	return;
}

void
function(void)
{
	ck_epoch_record_t *record;
	struct object *n;

	record = malloc(sizeof *record);
	ck_epoch_register(&epoch, record);

	n = malloc(sizeof *n);
	if (n == NULL)
		return;

	n->value = 1;

	/*
	 * We are using an epoch section here because there are multiple
	 * writers. It is also an option to use other forms of blocking
	 * write-side synchronization such as mutexes.
	 */
	ck_epoch_begin(epoch, record);
	n = ck_pr_fas_ptr(&global, n);
	ck_epoch_end(epoch, record);

	/* Defer destruction of previous object. */
	ck_epoch_call(record, &n->epoch_entry, destroy_object);

	/* Poll epoch sub-system in non-blocking manner. */
	ck_epoch_poll(&epoch, record);
	return;
}
.Ed
.Sh RETURN VALUES
This function has no return value.
.Sh ERRORS
The object pointed to by
.Fa record
must have been previously registered via
.Fn ck_epoch_register 3 .
.Sh SEE ALSO
.Xr ck_epoch_init 3 ,
.Xr ck_epoch_register 3 ,
.Xr ck_epoch_unregister 3 ,
.Xr ck_epoch_recycle 3 ,
.Xr ck_epoch_poll 3 ,
.Xr ck_epoch_synchronize 3 ,
.Xr ck_epoch_reclaim 3 ,
.Xr ck_epoch_barrier 3 ,
.Xr ck_epoch_begin 3 ,
.Xr ck_epoch_end 3
.Pp
Additional information available at http://concurrencykit.org/
