Allow slack stealing to be enabled / disabled via the config file.

2 files changed, 58 insertions, 42 deletions

diff --git a/litmus/Kconfig b/litmus/Kconfig
index ad8dc8308cf0..46563edf513c 100644
--- a/litmus/Kconfig
+++ b/litmus/Kconfig
@@ -34,6 +34,14 @@ config RELEASE_MASTER
            (http://www.cs.unc.edu/~anderson/papers.html).
            Currently only supported by GSN-EDF.
 
+config EDF_HSB_SLACK_STEALING
+       bool "EDF-HSB Slack Stealing"
+       depends on ARCH_HAS_SEND_PULL_TIMERS
+       default y
+       help
+          Allow servers in EDF-HSB to donate slack when they have no real-time
+          tasks to execute.
+
 endmenu
 
 menu "Real-Time Synchronization"
diff --git a/litmus/sched_edf_hsb.c b/litmus/sched_edf_hsb.c
index e5d5c5faa834..658a85c7177b 100644
--- a/litmus/sched_edf_hsb.c
+++ b/litmus/sched_edf_hsb.c
@@ -325,6 +325,7 @@ static void donate_slack(server_t *donator)
         add_slack(slack);
 }
 
+#ifdef CONFIG_EDF_HSB_SLACK_STEALING
 /*
  * Donate any available slack from a server.
  */
@@ -387,6 +388,55 @@ static void check_slack_candidate(struct task_struct *task)
 }
 
 /*
+ * Returns the next eligible slack server. This will remove any expired
+ * slack servers still present in the list.
+ */
+static noinline server_t* next_eligible_slack_server(void)
+{
+        server_t *next_slack = NULL;
+
+        while (!list_empty(&slack_queue)) {
+                next_slack = list_entry(slack_queue.next, server_t, list);
+                BUG_ON(!next_slack);
+
+                if (lt_after(next_slack->deadline, litmus_clock()) &&
+                    lt_after(next_slack->budget, SLACK_MIN)) {
+                        break;
+                } else {
+                        /* Slack has expired or has too little time */
+                        remove_slack(next_slack);
+                        next_slack = NULL;
+                }
+        }
+
+        return next_slack;
+}
+
+/*
+ * Returns the next SRT task that is tardy or will be tardy. If none
+ * are available, will return a tardy BE task if present.
+ */
+static noinline struct task_struct* next_eligible_slack(void)
+{
+        struct task_struct *next = get_candidate(slack_candidates.next);
+
+        /* We couldn't find an SRT to schedule. Find a BE which is
+         * either tardy or cannot run due to a lack of servers.
+         */
+        if (!next) {
+                next = __peek_ready(&be_domain);
+        }
+        return next;
+}
+
+#else
+#define check_donate_slack(a, b)
+#define check_slack_candidate(a)
+#define next_eligible_slack_server() (NULL)
+#define next_eligible_slack() (NULL)
+#endif
+
+/*
  * Order BE tasks FIFO.
  */
 static inline int be_higher_prio(struct task_struct *first, struct task_struct *second)
@@ -937,48 +987,6 @@ static noinline int catchup_srt_server(struct task_struct *task)
 }
 
 /*
- * Returns the next eligible slack server. This will remove any expired
- * slack servers still present in the list.
- */
-static noinline server_t* next_eligible_slack_server(void)
-{
-        server_t *next_slack = NULL;
-
-        while (!list_empty(&slack_queue)) {
-                next_slack = list_entry(slack_queue.next, server_t, list);
-                BUG_ON(!next_slack);
-
-                if (lt_after(next_slack->deadline, litmus_clock()) &&
-                    lt_after(next_slack->budget, SLACK_MIN)) {
-                        break;
-                } else {
-                        /* Slack has expired or has too little time */
-                        remove_slack(next_slack);
-                        next_slack = NULL;
-                }
-        }
-
-        return next_slack;
-}
-
-/*
- * Returns the next SRT task that is tardy or will be tardy. If none
- * are available, will return a tardy BE task if present.
- */
-static noinline struct task_struct* next_eligible_slack(void)
-{
-        struct task_struct *next = get_candidate(slack_candidates.next);
-
-        /* We couldn't find an SRT to schedule. Find a BE which is
-         * either tardy or cannot run due to a lack of servers.
-         */
-        if (!next) {
-                next = __peek_ready(&be_domain);
-        }
-        return next;
-}
-
-/*
  * If the server is eligible, return the next eligible job. If the server is
  * ineligible or there are no eligible jobs, returns NULL. This will re-release
  * any servers that are behind.