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Fix formatting of cond_signal().

.\"	$OpenBSD: cond_init.9,v 1.3 2022/03/11 14:42:08 visa Exp $ */
.\"
.\" Copyright (c) 2017 David Gwynne <dlg@openbsd.org>
.\"
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.\" purpose with or without fee is hereby granted, provided that the above
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.Dd $Mdocdate: March 11 2022 $
.Dt COND_INIT 9
.Os
.Sh NAME
.Nm cond_init ,
.Nm cond_wait ,
.Nm cond_signal ,
.Nm COND_INITIALIZER
.Nd wait condition API
.Sh SYNOPSIS
.In sys/systm.h
.Ft void
.Fn "cond_init" "struct cond *c"
.Ft void
.Fn "cond_wait" "struct cond *c" "const char *wmesg"
.Ft void
.Fn "cond_signal" "struct cond *c"
.Fn "COND_INITIALIZER"
.Sh DESCRIPTION
The wait condition API allows a thread to sleep while it waits for
a notification, aka signal, that pending work has completed.
.Pp
.Fn cond_init
initialises the wait condition
.Fa c
for use.
.Pp
.Fn cond_wait
is used to sleep on the wait condition
.Fa c
until whatever the thread is waiting on calls
.Fn cond_signal .
.Fa wmesg
is a pointer to a character string indicating the reason the thread
is sleeping.
.Pp
.Fn cond_signal
is used to notify the thread waiting on
.Fa c
that the work has finished and it may proceed.
.Pp
.Fn COND_INITIALIZER
initialises a declaration of a cond for use.
.Sh CONTEXT
.Fn cond_init ,
and
.Fn cond_signal
can be called during autoconf, from process context, or from interrupt
context.
.Pp
.Fn cond_wait
can be called from process context.
.Sh EXAMPLES
.Xr taskq_barrier 9
is implemented using the wait condition API.
The following is a commented copy of the implementation:
.Bd -literal
static void	taskq_barrier_task(void *);

void
taskq_barrier(struct taskq *tq)
{
	struct cond c;
	struct task t;

	/*
	 * any currently running work has to have finished
	 * before this new task can be run.
	 */

	cond_init(&c);
	task_init(&t, taskq_barrier_task, &c);

	task_add(tq, &t);

	/* wait until the task runs and signals completion */
	cond_wait(&c, "tqbar");
}

static void
taskq_barrier_task(void *p)
{
	struct cond *c = p;

	/*
	 * all previous tasks have run, signal the thread waiting
	 * in taskq_barrier
	 */

	cond_signal(c);
}
.Ed