[ported from 2008.3] Add synchronous task release API

3 files changed, 111 insertions, 4 deletions

diff --git a/litmus/Makefile b/litmus/Makefile
index f4c2d564cd0b..e93f19bb2016 100644
--- a/litmus/Makefile
+++ b/litmus/Makefile
@@ -4,6 +4,7 @@
 
 obj-y     = sched_plugin.o litmus.o \
             jobs.o \
+            sync.o \
             heap.o
 
 obj-$(CONFIG_FEATHER_TRACE) += ft_event.o ftdev.o
diff --git a/litmus/litmus.c b/litmus/litmus.c
index eb0d17e298d7..9254f1621af7 100644
--- a/litmus/litmus.c
+++ b/litmus/litmus.c
@@ -1,4 +1,6 @@
-/* litmus.c -- Implementation of the LITMUS syscalls, the LITMUS intialization code,
+/*
+ * litmus.c -- Implementation of the LITMUS syscalls,
+ *             the LITMUS intialization code,
  *             and the procfs interface..
  */
 #include <asm/uaccess.h>
@@ -438,10 +440,10 @@ static struct sysrq_key_op sysrq_kill_rt_tasks_op = {
         .help_msg       = "quit-rt-tasks(X)",
         .action_msg     = "sent SIGKILL to all LITMUS^RT real-time tasks",
 };
-
-
 #endif
 
+/* in litmus/sync.c */
+int count_tasks_waiting_for_release(void);
 
 static int proc_read_stats(char *page, char **start,
                            off_t off, int count,
@@ -453,7 +455,7 @@ static int proc_read_stats(char *page, char **start,
                        "real-time tasks   = %d\n"
                        "ready for release = %d\n",
                        atomic_read(&rt_task_count),
-                       0);
+                       count_tasks_waiting_for_release());
         return len;
 }
 
diff --git a/litmus/sync.c b/litmus/sync.c
new file mode 100644
index 000000000000..bf75fde5450b
--- /dev/null
+++ b/litmus/sync.c
@@ -0,0 +1,104 @@
+/* litmus/sync.c - Support for synchronous and asynchronous task system releases.
+ *
+ *
+ */
+
+#include <asm/atomic.h>
+#include <asm/uaccess.h>
+#include <linux/spinlock.h>
+#include <linux/list.h>
+#include <linux/sched.h>
+#include <linux/completion.h>
+
+#include <litmus/litmus.h>
+#include <litmus/sched_plugin.h>
+#include <litmus/jobs.h>
+
+#include <litmus/sched_trace.h>
+
+static DECLARE_COMPLETION(ts_release);
+
+static long do_wait_for_ts_release(void)
+{
+        long ret = 0;
+
+        /* If the interruption races with a release, the completion object
+         * may have a non-zero counter. To avoid this problem, this should
+         * be replaced by wait_for_completion().
+         *
+         * For debugging purposes, this is interruptible for now.
+         */
+        ret = wait_for_completion_interruptible(&ts_release);
+
+        return ret;
+}
+
+int count_tasks_waiting_for_release(void)
+{
+        unsigned long flags;
+        int task_count = 0;
+        struct list_head *pos;
+
+        spin_lock_irqsave(&ts_release.wait.lock, flags);
+        list_for_each(pos, &ts_release.wait.task_list) {
+                task_count++;
+        }
+        spin_unlock_irqrestore(&ts_release.wait.lock, flags);
+
+        return task_count;
+}
+
+static long do_release_ts(lt_t start)
+{
+        int  task_count = 0;
+        unsigned long flags;
+        struct list_head        *pos;
+        struct task_struct      *t;
+
+
+        spin_lock_irqsave(&ts_release.wait.lock, flags);
+        TRACE("<<<<<< synchronous task system release >>>>>>\n");
+
+        sched_trace_sys_release(&start);
+        list_for_each(pos, &ts_release.wait.task_list) {
+                t = (struct task_struct*) list_entry(pos,
+                                                     struct __wait_queue,
+                                                     task_list)->private;
+                task_count++;
+                litmus->release_at(t, start + t->rt_param.task_params.phase);
+                sched_trace_task_release(t);
+        }
+
+        spin_unlock_irqrestore(&ts_release.wait.lock, flags);
+
+        complete_n(&ts_release, task_count);
+
+        return task_count;
+}
+
+
+asmlinkage long sys_wait_for_ts_release(void)
+{
+        long ret = -EPERM;
+        struct task_struct *t = current;
+
+        if (is_realtime(t))
+                ret = do_wait_for_ts_release();
+
+        return ret;
+}
+
+
+asmlinkage long sys_release_ts(lt_t __user *__delay)
+{
+        long ret;
+        lt_t delay;
+
+        /* FIXME: check capabilities... */
+
+        ret = copy_from_user(&delay, __delay, sizeof(delay));
+        if (ret == 0)
+                ret = do_release_ts(litmus_clock() + delay);
+
+        return ret;
+}