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.Dd September 2, 2012
.Dt CK_EPOCH_BARRIER 3
.Sh NAME
.Nm ck_epoch_barrier
.Nd block until a grace period and all callbacks have been dispatched
.Sh LIBRARY
Concurrency Kit (libck, \-lck)
.Sh SYNOPSIS
.In ck_epoch.h
.Ft void
.Fn ck_epoch_barrier "ck_epoch_t *epoch" "ck_epoch_record_t *record"
.Sh DESCRIPTION
The
.Fn ck_epoch_barrier 3
function will block the caller until a grace period has been
detected, according to the semantics of epoch reclamation.
Any objects requiring safe memory reclamation which are logically
deleted are safe for physical deletion following a call to
.Fn ck_epoch_barrier 3 . This function will also dispatch all callbacks
associated with
.Fa epoch
that were previously scheduled via
.Fn ck_epoch_call 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.
 * stack was previously initialized with ck_stack_init.
 */
ck_epoch_t *epoch;
ck_stack_t *stack;

void
function(void)
{
	ck_epoch_record_t *record;
	ck_stack_entry_t *s;

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

	/*
	 * We are using an epoch section here to guarantee no
	 * nodes in the stack are deleted while we are dereferencing
	 * them. This is needed here because there are multiple writers.
	 * If there was only one thread popping from the this stack,
	 * then there is no need to ck_epoch_begin/ck_epoch_end.
	 */
	ck_epoch_begin(epoch, record);

	/* Logically delete an object. */
	s = ck_stack_pop_upmc(stack);

	ck_epoch_end(epoch, record);

	/*
	 * Wait until no threads could possibly have a reference to the
	 * object we just popped (assume all threads are simply executing
	 * ck_stack_pop_upmc).
	 */
	ck_epoch_barrier(epoch, record);

	/* It is now safe to physically delete the object. */
	free(s);
	return;
}
.Ed
.Sh RETURN VALUES
This function has no return value.
.Sh ERRORS
Behavior is undefined if the object pointed to by
.Fa epoch
is not a valid epoch object. 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_call 3 ,
.Xr ck_epoch_begin 3 ,
.Xr ck_epoch_end 3
.Pp
Additional information available at http://concurrencykit.org/
