Infrastructure for Litmus signals.prop/litmus-signals

Added signals to Litmus. Specifcally, SIG_BUDGET signals
are delivered (when requested by real-time tasks) when
a budget is exceeded.

Note: pfair not currently supported (but it probably could be).

3 files changed, 79 insertions, 4 deletions

diff --git a/include/litmus/budget.h b/include/litmus/budget.h
index 33344ee8d5f9..763b31c0e9f6 100644
--- a/include/litmus/budget.h
+++ b/include/litmus/budget.h
@@ -5,6 +5,9 @@
  * the next task. */
 void update_enforcement_timer(struct task_struct* t);
 
+/* Send SIG_BUDGET to a real-time task. */
+void send_sigbudget(struct task_struct* t);
+
 inline static int budget_exhausted(struct task_struct* t)
 {
         return get_exec_time(t) >= get_exec_cost(t);
@@ -19,10 +22,21 @@ inline static lt_t budget_remaining(struct task_struct* t)
                 return 0;
 }
 
-#define budget_enforced(t) (tsk_rt(t)->task_params.budget_policy != NO_ENFORCEMENT)
+#define budget_enforced(t) (\
+        tsk_rt(t)->task_params.budget_policy != NO_ENFORCEMENT)
+
+#define budget_precisely_tracked(t) (\
+        tsk_rt(t)->task_params.budget_policy == PRECISE_ENFORCEMENT || \
+        tsk_rt(t)->task_params.budget_signal_policy == PRECISE_SIGNALS)
+
+#define budget_signalled(t) (\
+        tsk_rt(t)->task_params.budget_signal_policy != NO_SIGNALS)
+
+#define budget_precisely_signalled(t) (\
+        tsk_rt(t)->task_params.budget_policy == PRECISE_SIGNALS)
 
-#define budget_precisely_enforced(t) (tsk_rt(t)->task_params.budget_policy \
-                                      == PRECISE_ENFORCEMENT)
+#define sigbudget_sent(t) (\
+        test_bit(RT_JOB_SIG_BUDGET_SENT, &tsk_rt(t)->job_params.flags))
 
 static inline int requeue_preempted_job(struct task_struct* t)
 {
diff --git a/include/litmus/rt_param.h b/include/litmus/rt_param.h
index 89ac0dda7d3d..637fe6b84f9d 100644
--- a/include/litmus/rt_param.h
+++ b/include/litmus/rt_param.h
@@ -30,9 +30,15 @@ typedef enum {
 typedef enum {
         NO_ENFORCEMENT,      /* job may overrun unhindered */
         QUANTUM_ENFORCEMENT, /* budgets are only checked on quantum boundaries */
-        PRECISE_ENFORCEMENT  /* budgets are enforced with hrtimers */
+        PRECISE_ENFORCEMENT, /* budgets are enforced with hrtimers */
 } budget_policy_t;
 
+typedef enum {
+        NO_SIGNALS,                     /* job receives no signals when it exhausts its budget */
+        QUANTUM_SIGNALS,        /* budget signals are only sent on quantum boundaries */
+        PRECISE_SIGNALS,        /* budget signals are triggered with hrtimers */
+} budget_signal_policy_t;
+
 /* We use the common priority interpretation "lower index == higher priority",
  * which is commonly used in fixed-priority schedulability analysis papers.
  * So, a numerically lower priority value implies higher scheduling priority,
@@ -62,6 +68,7 @@ struct rt_task {
         unsigned int    priority;
         task_class_t    cls;
         budget_policy_t budget_policy; /* ignored by pfair */
+        budget_signal_policy_t budget_signal_policy; /* currently ignored by pfair */
 };
 
 union np_flag {
@@ -118,8 +125,15 @@ struct rt_job {
          * Increase this sequence number when a job is released.
          */
         unsigned int    job_no;
+
+        /* bits:
+         * 0th: Set if a budget exhaustion signal has already been sent for
+         *      the current job. */
+        unsigned long   flags;
 };
 
+#define RT_JOB_SIG_BUDGET_SENT  0
+
 struct pfair_param;
 
 /*      RT task parameters for scheduling extensions
diff --git a/include/litmus/signal.h b/include/litmus/signal.h
new file mode 100644
index 000000000000..b3d82b294984
--- /dev/null
+++ b/include/litmus/signal.h
@@ -0,0 +1,47 @@
+#ifndef LITMUS_SIGNAL_H
+#define LITMUS_SIGNAL_H
+
+#ifdef __KERNEL__
+#include <linux/signal.h>
+#else
+#include <signal.h>
+#endif
+
+/* Signals used by Litmus to asynchronously communicate events
+ * to real-time tasks.
+ * 
+ * Signal values overlap with [SIGRTMIN, SIGRTMAX], so beware of
+ * application-level conflicts when dealing with COTS user-level
+ * code.
+ */
+
+/* Sent to a Litmus task when all of the following conditions are true:
+ * (1) The task has exhausted its budget.
+ * (2) budget_signal_policy is QUANTUM_SIGNALS or PRECISE_SIGNALS.
+ *
+ * Note: If a task does not have a registered handler for SIG_BUDGET,
+ * the signal will cause the task to terminate (default action).
+ */
+
+/* Assigned values start at SIGRTMAX and decrease, hopefully reducing
+ * likelihood of user-level conflicts.
+ */
+#define SIG_BUDGET                                      (SIGRTMAX - 0)
+
+/*
+Future signals could include:
+
+#define SIG_DEADLINE_MISS                       (SIGRTMAX - 1)
+#define SIG_CRIT_LEVEL_CHANGE           (SIGRTMAX - 2)
+*/
+
+#define SIGLITMUSMIN                            SIG_BUDGET
+
+#ifdef __KERNEL__
+#if (SIGLITMUSMIN < SIGRTMIN)
+/* no compile-time check in user-space since SIGRTMIN may be a variable. */
+#error "Too many LITMUS^RT signals!"
+#endif
+#endif
+
+#endif