[ported from 2008.3] Add common EDF functions

1 files changed, 102 insertions, 0 deletions

diff --git a/litmus/edf_common.c b/litmus/edf_common.c
new file mode 100644
index 000000000000..97e37761cedc
--- /dev/null
+++ b/litmus/edf_common.c
@@ -0,0 +1,102 @@
+/*
+ * kernel/edf_common.c
+ *
+ * Common functions for EDF based scheduler.
+ */
+
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/list.h>
+
+#include <litmus/litmus.h>
+#include <litmus/sched_plugin.h>
+#include <litmus/sched_trace.h>
+
+#include <litmus/edf_common.h>
+
+/* edf_higher_prio -  returns true if first has a higher EDF priority
+ *                    than second. Deadline ties are broken by PID.
+ *
+ * both first and second may be NULL
+ */
+int edf_higher_prio(struct task_struct* first,
+                    struct task_struct* second)
+{
+        struct task_struct *first_task = first;
+        struct task_struct *second_task = second;
+
+        /* There is no point in comparing a task to itself. */
+        if (first && first == second) {
+                TRACE_TASK(first,
+                           "WARNING: pointless edf priority comparison.\n");
+                return 0;
+        }
+
+
+        /* Check for inherited priorities. Change task
+         * used for comparison in such a case.
+         */
+        if (first && first->rt_param.inh_task)
+                first_task = first->rt_param.inh_task;
+        if (second && second->rt_param.inh_task)
+                second_task = second->rt_param.inh_task;
+
+        return
+                /* it has to exist in order to have higher priority */
+                first_task && (
+                /* does the second task exist and is it a real-time task?  If
+                 * not, the first task (which is a RT task) has higher
+                 * priority.
+                 */
+                !second_task || !is_realtime(second_task)  ||
+
+                /* is the deadline of the first task earlier?
+                 * Then it has higher priority.
+                 */
+                earlier_deadline(first_task, second_task) ||
+
+                /* Do we have a deadline tie?
+                 * Then break by PID.
+                 */
+                (get_deadline(first_task) == get_deadline(second_task) &&
+                (first_task->pid < second_task->pid ||
+
+                /* If the PIDs are the same then the task with the inherited
+                 * priority wins.
+                 */
+                (first_task->pid == second_task->pid &&
+                 !second->rt_param.inh_task))));
+}
+
+int edf_ready_order(struct heap_node* a, struct heap_node* b)
+{
+        return edf_higher_prio(heap2task(a), heap2task(b));
+}
+
+void edf_domain_init(rt_domain_t* rt, check_resched_needed_t resched,
+                      release_jobs_t release)
+{
+        rt_domain_init(rt,  edf_ready_order, resched, release);
+}
+
+/* need_to_preempt - check whether the task t needs to be preempted
+ *                   call only with irqs disabled and with  ready_lock acquired
+ *                   THIS DOES NOT TAKE NON-PREEMPTIVE SECTIONS INTO ACCOUNT!
+ */
+int edf_preemption_needed(rt_domain_t* rt, struct task_struct *t)
+{
+        /* we need the read lock for edf_ready_queue */
+        /* no need to preempt if there is nothing pending */
+        if (!__jobs_pending(rt))
+                return 0;
+        /* we need to reschedule if t doesn't exist */
+        if (!t)
+                return 1;
+
+        /* NOTE: We cannot check for non-preemptibility since we
+         *       don't know what address space we're currently in.
+         */
+
+        /* make sure to get non-rt stuff out of the way */
+        return !is_realtime(t) || edf_higher_prio(__next_ready(rt), t);
+}