4 files changed, 194 insertions, 0 deletions
diff --git a/kern/Makefile b/kern/Makefile
index 0d848cca..ab7d6b59 100644
--- a/kern/Makefile
+++ b/kern/Makefile
@@ -1,6 +1,7 @@
 x15_SOURCES-y += \
         kern/arg.c \
         kern/bitmap.c \
+        kern/bulletin.c \
         kern/cbuf.c \
         kern/clock.c \
         kern/condition.c \
diff --git a/kern/bulletin.c b/kern/bulletin.c
new file mode 100644
index 00000000..bbb1bfc3
--- /dev/null
+++ b/kern/bulletin.c
@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2017-2018 Richard Braun.
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <assert.h>
+#include <stdint.h>
+
+#include <kern/bulletin.h>
+#include <kern/list.h>
+#include <kern/rcu.h>
+#include <kern/spinlock.h>
+#include <kern/thread.h>
+
+static void
+bulletin_sub_init(struct bulletin_sub *sub,
+                  bulletin_notif_fn_t notif_fn, void *arg)
+{
+    sub->notif_fn = notif_fn;
+    sub->arg = arg;
+}
+
+static void
+bulletin_sub_notify(const struct bulletin_sub *sub, uintptr_t value)
+{
+    sub->notif_fn(value, sub->arg);
+}
+
+void
+bulletin_init(struct bulletin *bulletin)
+{
+    spinlock_init(&bulletin->lock);
+    list_init(&bulletin->subs);
+}
+
+void
+bulletin_subscribe(struct bulletin *bulletin, struct bulletin_sub *sub,
+                   bulletin_notif_fn_t notif_fn, void *arg)
+{
+    bulletin_sub_init(sub, notif_fn, arg);
+
+    spinlock_lock(&bulletin->lock);
+    list_rcu_insert_tail(&bulletin->subs, &sub->node);
+    spinlock_unlock(&bulletin->lock);
+}
+
+void
+bulletin_unsubscribe(struct bulletin *bulletin, struct bulletin_sub *sub)
+{
+    spinlock_lock(&bulletin->lock);
+    list_rcu_remove(&sub->node);
+    spinlock_unlock(&bulletin->lock);
+
+    rcu_wait();
+}
+
+void
+bulletin_publish(struct bulletin *bulletin, uintptr_t value)
+{
+    struct bulletin_sub *sub;
+
+    assert(!thread_interrupted());
+
+    rcu_read_enter();
+
+    list_rcu_for_each_entry(&bulletin->subs, sub, node) {
+        bulletin_sub_notify(sub, value);
+    }
+
+    rcu_read_leave();
+}
diff --git a/kern/bulletin.h b/kern/bulletin.h
new file mode 100644
index 00000000..8ce9d9e4
--- /dev/null
+++ b/kern/bulletin.h
@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2017-2018 Richard Braun.
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ * Minimalist publish-subscribe mechanism.
+ */
+
+#ifndef KERN_BULLETIN_H
+#define KERN_BULLETIN_H
+
+#include <stdint.h>
+
+#include <kern/macros.h>
+#include <kern/work.h>
+
+/*
+ * Type for bulletin notification functions.
+ *
+ * The value is passed from the publisher unmodified, and can safely be
+ * cast into a pointer. Notification functions run in the context of the
+ * publisher.
+ */
+typedef void (*bulletin_notif_fn_t)(uintptr_t value, void *arg);
+
+#include <kern/bulletin_i.h>
+
+struct bulletin;
+
+/*
+ * Bulletin subscriber.
+ */
+struct bulletin_sub;
+
+void bulletin_init(struct bulletin *bulletin);
+
+/*
+ * Subscribe to a bulletin.
+ *
+ * Once subscribed, the notification function is called with its argument
+ * each time the bulletin is published.
+ */
+void bulletin_subscribe(struct bulletin *bulletin, struct bulletin_sub *sub,
+                        bulletin_notif_fn_t notif_fn, void *arg);
+
+/*
+ * Unsubscribe from a bulletin.
+ *
+ * On return, the subscriber notification function may not be called any more.
+ *
+ * This function synchronizes with RCU.
+ */
+void bulletin_unsubscribe(struct bulletin *bulletin, struct bulletin_sub *sub);
+
+/*
+ * Publish a bulletin.
+ *
+ * All subscribers are notified by calling their notification function, with
+ * the given value passed unmodified.
+ */
+void bulletin_publish(struct bulletin *bulletin, uintptr_t value);
+
+#endif /* KERN_BULLETIN_H */
diff --git a/kern/bulletin_i.h b/kern/bulletin_i.h
new file mode 100644
index 00000000..ea0940a8
--- /dev/null
+++ b/kern/bulletin_i.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2017-2018 Richard Braun.
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef KERN_BULLETIN_I_H
+#define KERN_BULLETIN_I_H
+
+#include <kern/list.h>
+#include <kern/spinlock.h>
+
+struct bulletin_sub {
+    struct list node;
+    bulletin_notif_fn_t notif_fn;
+    void *arg;
+};
+
+struct bulletin {
+    struct spinlock lock;
+    struct list subs;
+};
+
+#endif /* KERN_BULLETIN_I_H */