1 files changed, 54 insertions, 0 deletions

diff --git a/litmus/pgm.c b/litmus/pgm.c
new file mode 100644
index 000000000000..f8b857de8118
--- /dev/null
+++ b/litmus/pgm.c
@@ -0,0 +1,54 @@
+/* litmus/pgm.c - common pgm control code
+ */
+
+#include <linux/sched.h>
+#include <litmus/litmus.h>
+#include <litmus/pgm.h>
+
+/* Only readjust release/deadline if difference is over a given threshold.
+   It's a weak method for accounting overheads. Ideally, we'd know the last
+   time t was woken up by its last predecessor, rather than having to look
+   at 'now'. */
+#define ADJUSTMENT_THRESH_US 200
+
+void setup_pgm_release(struct task_struct* t)
+{
+        /* approximate time last predecessor gave us tokens */
+        lt_t now = litmus_clock();
+
+        TRACE_TASK(t, "is starting a new PGM job: waiting:%d  satisfied:%d\n",
+                tsk_rt(t)->ctrl_page->pgm_waiting, tsk_rt(t)->ctrl_page->pgm_satisfied);
+
+        BUG_ON(!tsk_rt(t)->ctrl_page->pgm_waiting || !tsk_rt(t)->ctrl_page->pgm_satisfied);
+
+        tsk_rt(t)->ctrl_page->pgm_waiting = 0;
+        tsk_rt(t)->ctrl_page->pgm_satisfied = 0;
+
+        /* Adjust release time if we got the last tokens after release of this job.
+           This is possible since PGM jobs are early-released. Don't shift our
+           deadline if we got the tokens earlier than expected. */
+        if (now > tsk_rt(t)->job_params.release) {
+                long long diff = now - tsk_rt(t)->job_params.release;
+                if (diff > ADJUSTMENT_THRESH_US) {
+                        lt_t adj_deadline = now + get_rt_relative_deadline(t);
+
+                        TRACE_TASK(t, "adjusting PGM release time from (r = %llu, d = %llu) "
+                                "to (r = %llu, d = %llu)\n",
+                                tsk_rt(t)->job_params.release, tsk_rt(t)->job_params.deadline,
+                                now, adj_deadline);
+
+                        tsk_rt(t)->job_params.release = now;
+                        tsk_rt(t)->job_params.deadline = adj_deadline;
+                        tsk_rt(t)->job_params.exec_time = 0; /* reset budget */
+                }
+                else {
+                        TRACE_TASK(t, "adjustment falls below threshold. %lld < %lld\n",
+                                diff, ADJUSTMENT_THRESH_US);
+                }
+        }
+        else {
+                TRACE_TASK(t, "got tokens early--no need to adjust release. "
+                        "cur time = %llu, release time = %llu\n",
+                        now, tsk_rt(t)->job_params.release);
+        }
+}