[take14 3/3] kevent: Timer notifications.

[Evgeniy Polyakov]

Timer notifications.

Timer notifications can be used for fine grained per-process time 
management, since interval timers are very inconvenient to use, 
and they are limited.

Signed-off-by: Evgeniy Polyakov <johnpol@xxxxxxxxxxx>

diff --git a/kernel/kevent/kevent_timer.c b/kernel/kevent/kevent_timer.c
new file mode 100644
index 0000000..b2fee61
--- /dev/null
+++ b/kernel/kevent/kevent_timer.c
@@ -0,0 +1,105 @@
+/*
+ * 2006 Copyright (c) Evgeniy Polyakov <johnpol@xxxxxxxxxxx>
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/timer.h>
+#include <linux/jiffies.h>
+#include <linux/kevent.h>
+
+struct kevent_timer
+{
+	struct timer_list	ktimer;
+	struct kevent_storage	ktimer_storage;
+};
+
+static void kevent_timer_func(unsigned long data)
+{
+	struct kevent *k = (struct kevent *)data;
+	struct timer_list *t = k->st->origin;
+
+	kevent_storage_ready(k->st, NULL, KEVENT_MASK_ALL);
+	mod_timer(t, jiffies + msecs_to_jiffies(k->event.id.raw[0]));
+}
+
+static struct lock_class_key kevent_timer_key;
+
+static int kevent_timer_enqueue(struct kevent *k)
+{
+	int err;
+	struct kevent_timer *t;
+
+	t = kmalloc(sizeof(struct kevent_timer), GFP_KERNEL);
+	if (!t)
+		return -ENOMEM;
+
+	setup_timer(&t->ktimer, &kevent_timer_func, (unsigned long)k);
+
+	err = kevent_storage_init(&t->ktimer, &t->ktimer_storage);
+	if (err)
+		goto err_out_free;
+	lockdep_set_class(&t->ktimer_storage.lock, &kevent_timer_key);
+
+	err = kevent_storage_enqueue(&t->ktimer_storage, k);
+	if (err)
+		goto err_out_st_fini;
+
+	mod_timer(&t->ktimer, jiffies + msecs_to_jiffies(k->event.id.raw[0]));
+
+	return 0;
+
+err_out_st_fini:
+	kevent_storage_fini(&t->ktimer_storage);
+err_out_free:
+	kfree(t);
+
+	return err;
+}
+
+static int kevent_timer_dequeue(struct kevent *k)
+{
+	struct kevent_storage *st = k->st;
+	struct kevent_timer *t = container_of(st, struct kevent_timer, ktimer_storage);
+
+	del_timer_sync(&t->ktimer);
+	kevent_storage_dequeue(st, k);
+	kfree(t);
+
+	return 0;
+}
+
+static int kevent_timer_callback(struct kevent *k)
+{
+	k->event.ret_data[0] = jiffies_to_msecs(jiffies);
+	return 1;
+}
+
+static int __init kevent_init_timer(void)
+{
+	struct kevent_callbacks tc = {
+		.callback = &kevent_timer_callback,
+		.enqueue = &kevent_timer_enqueue,
+		.dequeue = &kevent_timer_dequeue};
+
+	return kevent_add_callbacks(&tc, KEVENT_TIMER);
+}
+module_init(kevent_init_timer);

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