Kernel daemon abstraction.
--- diff/drivers/md/Makefile	2003-12-09 11:11:49.000000000 +0000
+++ source/drivers/md/Makefile	2003-12-09 11:10:48.000000000 +0000
@@ -4,12 +4,12 @@
 
 O_TARGET	:= mddev.o
 
-export-objs	:= md.o xor.o dm-table.o dm-target.o dm.o
+export-objs	:= md.o xor.o dm-table.o dm-target.o dm.o dm-daemon.o
 
 list-multi	:= lvm-mod.o dm-mod.o dm-mirror-mod.o
 lvm-mod-objs	:= lvm.o lvm-snap.o lvm-fs.o
 dm-mod-objs	:= dm.o dm-table.o dm-target.o dm-linear.o dm-stripe.o \
-		   dm-ioctl.o
+		   dm-ioctl.o dm-daemon.o
 
 # Note: link order is important.  All raid personalities
 # and xor.o must come before md.o, as they each initialise 
--- diff/drivers/md/dm-daemon.c	1970-01-01 01:00:00.000000000 +0100
+++ source/drivers/md/dm-daemon.c	2003-12-09 11:09:56.000000000 +0000
@@ -0,0 +1,113 @@
+/*
+ * Copyright (C) 2003 Sistina Software
+ *
+ * This file is released under the LGPL.
+ */
+
+#include "dm.h"
+#include "dm-daemon.h"
+
+#include <linux/module.h>
+#include <linux/sched.h>
+
+static int daemon(void *arg)
+{
+	struct dm_daemon *dd = (struct dm_daemon *) arg;
+	DECLARE_WAITQUEUE(wq, current);
+
+	daemonize();
+	reparent_to_init();
+
+	/* block all signals */
+	spin_lock_irq(&current->sigmask_lock);
+	sigfillset(&current->blocked);
+	flush_signals(current);
+	spin_unlock_irq(&current->sigmask_lock);
+
+	strcpy(current->comm, dd->name);
+	atomic_set(&dd->please_die, 0);
+
+	add_wait_queue(&dd->job_queue, &wq);
+
+	down(&dd->run_lock);
+	up(&dd->start_lock);
+
+	/*
+	 * dd->fn() could do anything, very likely it will
+	 * suspend.  So we can't set the state to
+	 * TASK_INTERRUPTIBLE before calling it.  In order to
+	 * prevent a race with a waking thread we do this little
+	 * dance with the dd->woken variable.
+	 */
+	while (1) {
+		do {
+			set_current_state(TASK_RUNNING);
+
+			if (atomic_read(&dd->please_die))
+				goto out;
+
+			atomic_set(&dd->woken, 0);
+			dd->fn();
+			yield();
+
+			set_current_state(TASK_INTERRUPTIBLE);
+		} while (atomic_read(&dd->woken));
+
+		schedule();
+	}
+
+ out:
+	remove_wait_queue(&dd->job_queue, &wq);
+	up(&dd->run_lock);
+	return 0;
+}
+
+int dm_daemon_start(struct dm_daemon *dd, const char *name, void (*fn)(void))
+{
+	pid_t pid = 0;
+
+	/*
+	 * Initialise the dm_daemon.
+	 */
+	dd->fn = fn;
+	strncpy(dd->name, name, sizeof(dd->name) - 1);
+	sema_init(&dd->start_lock, 1);
+	sema_init(&dd->run_lock, 1);
+	init_waitqueue_head(&dd->job_queue);
+
+	/*
+	 * Start the new thread.
+	 */
+	down(&dd->start_lock);
+	pid = kernel_thread(daemon, dd, 0);
+	if (pid <= 0) {
+		DMERR("Failed to start %s thread", name);
+		return -EAGAIN;
+	}
+
+	/*
+	 * wait for the daemon to up this mutex.
+	 */
+	down(&dd->start_lock);
+	up(&dd->start_lock);
+
+	return 0;
+}
+
+void dm_daemon_stop(struct dm_daemon *dd)
+{
+	atomic_set(&dd->please_die, 1);
+	dm_daemon_wake(dd);
+	down(&dd->run_lock);
+	up(&dd->run_lock);
+}
+
+void dm_daemon_wake(struct dm_daemon *dd)
+{
+	atomic_set(&dd->woken, 1);
+	wake_up_interruptible(&dd->job_queue);
+}
+
+EXPORT_SYMBOL(dm_daemon_start);
+EXPORT_SYMBOL(dm_daemon_stop);
+EXPORT_SYMBOL(dm_daemon_wake);
--- diff/drivers/md/dm-daemon.h	1970-01-01 01:00:00.000000000 +0100
+++ source/drivers/md/dm-daemon.h	2003-12-09 11:09:56.000000000 +0000
@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2003 Sistina Software
+ *
+ * This file is released under the LGPL.
+ */
+
+#ifndef DM_DAEMON_H
+#define DM_DAEMON_H
+
+#include <asm/atomic.h>
+#include <asm/semaphore.h>
+
+struct dm_daemon {
+	void (*fn)(void);
+	char name[16];
+	atomic_t please_die;
+	struct semaphore start_lock;
+	struct semaphore run_lock;
+
+	atomic_t woken;
+	wait_queue_head_t job_queue;
+};
+
+int dm_daemon_start(struct dm_daemon *dd, const char *name, void (*fn)(void));
+void dm_daemon_stop(struct dm_daemon *dd);
+void dm_daemon_wake(struct dm_daemon *dd);
+int dm_daemon_running(struct dm_daemon *dd);
+
+#endif