Extend task_struct with rt_param

This patch adds the PCB extensions required for LITMUS^RT.

2 files changed, 296 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index f425eb3318ab..b52aa2d1d3e8 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -126,6 +126,8 @@ struct sched_attr {
         u64 sched_period;
 };
 
+#include <litmus/rt_param.h>
+
 struct futex_pi_state;
 struct robust_list_head;
 struct bio_list;
@@ -1886,6 +1888,9 @@ struct task_struct {
         int nr_dirtied_pause;
         unsigned long dirty_paused_when; /* start of a write-and-pause period */
 
+        /* LITMUS RT parameters and state */
+        struct rt_param rt_param;
+
 #ifdef CONFIG_LATENCYTOP
         int latency_record_count;
         struct latency_record latency_record[LT_SAVECOUNT];
diff --git a/include/litmus/rt_param.h b/include/litmus/rt_param.h
new file mode 100644
index 000000000000..8c7869f46bfb
--- /dev/null
+++ b/include/litmus/rt_param.h
@@ -0,0 +1,291 @@
+/*
+ * Definition of the scheduler plugin interface.
+ *
+ */
+#ifndef _LINUX_RT_PARAM_H_
+#define _LINUX_RT_PARAM_H_
+
+/* Litmus time type. */
+typedef unsigned long long lt_t;
+
+static inline int lt_after(lt_t a, lt_t b)
+{
+        return ((long long) b) - ((long long) a) < 0;
+}
+#define lt_before(a, b) lt_after(b, a)
+
+static inline int lt_after_eq(lt_t a, lt_t b)
+{
+        return ((long long) a) - ((long long) b) >= 0;
+}
+#define lt_before_eq(a, b) lt_after_eq(b, a)
+
+/* different types of clients */
+typedef enum {
+        RT_CLASS_HARD,
+        RT_CLASS_SOFT,
+        RT_CLASS_BEST_EFFORT
+} task_class_t;
+
+typedef enum {
+        NO_ENFORCEMENT,      /* job may overrun unhindered */
+        QUANTUM_ENFORCEMENT, /* budgets are only checked on quantum boundaries */
+        PRECISE_ENFORCEMENT  /* budgets are enforced with hrtimers */
+} budget_policy_t;
+
+/* Release behaviors for jobs. PERIODIC and EARLY jobs
+   must end by calling sys_complete_job() (or equivalent)
+   to set up their next release and deadline. */
+typedef enum {
+        /* Jobs are released sporadically (provided job precedence
+       constraints are met). */
+        TASK_SPORADIC,
+
+        /* Jobs are released periodically (provided job precedence
+       constraints are met). */
+        TASK_PERIODIC,
+
+    /* Jobs are released immediately after meeting precedence
+       constraints. Beware this can peg your CPUs if used in
+       the wrong applications. Only supported by EDF schedulers. */
+        TASK_EARLY
+} release_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,
+ * with priority 1 being the highest priority. Priority 0 is reserved for
+ * priority boosting. LITMUS_MAX_PRIORITY denotes the maximum priority value
+ * range.
+ */
+
+#define LITMUS_MAX_PRIORITY     512
+#define LITMUS_HIGHEST_PRIORITY   1
+#define LITMUS_LOWEST_PRIORITY    (LITMUS_MAX_PRIORITY - 1)
+
+/* Provide generic comparison macros for userspace,
+ * in case that we change this later. */
+#define litmus_higher_fixed_prio(a, b)  (a < b)
+#define litmus_lower_fixed_prio(a, b)   (a > b)
+#define litmus_is_valid_fixed_prio(p)           \
+        ((p) >= LITMUS_HIGHEST_PRIORITY &&      \
+         (p) <= LITMUS_LOWEST_PRIORITY)
+
+struct rt_task {
+        lt_t            exec_cost;
+        lt_t            period;
+        lt_t            relative_deadline;
+        lt_t            phase;
+        unsigned int    cpu;
+        unsigned int    priority;
+        task_class_t    cls;
+        budget_policy_t  budget_policy;  /* ignored by pfair */
+        release_policy_t release_policy;
+};
+
+union np_flag {
+        uint64_t raw;
+        struct {
+                /* Is the task currently in a non-preemptive section? */
+                uint64_t flag:31;
+                /* Should the task call into the scheduler? */
+                uint64_t preempt:1;
+        } np;
+};
+
+/* The definition of the data that is shared between the kernel and real-time
+ * tasks via a shared page (see litmus/ctrldev.c).
+ *
+ * WARNING: User space can write to this, so don't trust
+ * the correctness of the fields!
+ *
+ * This servees two purposes: to enable efficient signaling
+ * of non-preemptive sections (user->kernel) and
+ * delayed preemptions (kernel->user), and to export
+ * some real-time relevant statistics such as preemption and
+ * migration data to user space. We can't use a device to export
+ * statistics because we want to avoid system call overhead when
+ * determining preemption/migration overheads).
+ */
+struct control_page {
+        /* This flag is used by userspace to communicate non-preempive
+         * sections. */
+        volatile union np_flag sched;
+
+        volatile uint64_t irq_count; /* Incremented by the kernel each time an IRQ is
+                                      * handled. */
+
+        /* Locking overhead tracing: userspace records here the time stamp
+         * and IRQ counter prior to starting the system call. */
+        uint64_t ts_syscall_start;  /* Feather-Trace cycles */
+        uint64_t irq_syscall_start; /* Snapshot of irq_count when the syscall
+                                     * started. */
+
+        /* to be extended */
+};
+
+/* Expected offsets within the control page. */
+
+#define LITMUS_CP_OFFSET_SCHED          0
+#define LITMUS_CP_OFFSET_IRQ_COUNT      8
+#define LITMUS_CP_OFFSET_TS_SC_START    16
+#define LITMUS_CP_OFFSET_IRQ_SC_START   24
+
+/* don't export internal data structures to user space (liblitmus) */
+#ifdef __KERNEL__
+
+struct _rt_domain;
+struct bheap_node;
+struct release_heap;
+
+struct rt_job {
+        /* Time instant the the job was or will be released.  */
+        lt_t    release;
+
+        /* What is the current deadline? */
+        lt_t    deadline;
+
+        /* How much service has this job received so far? */
+        lt_t    exec_time;
+
+        /* By how much did the prior job miss its deadline by?
+         * Value differs from tardiness in that lateness may
+         * be negative (when job finishes before its deadline).
+         */
+        long long       lateness;
+
+        /* Which job is this. This is used to let user space
+         * specify which job to wait for, which is important if jobs
+         * overrun. If we just call sys_sleep_next_period() then we
+         * will unintentionally miss jobs after an overrun.
+         *
+         * Increase this sequence number when a job is released.
+         */
+        unsigned int    job_no;
+
+#ifdef CONFIG_SCHED_TASK_TRACE
+        /* Keep track of the last time the job suspended.
+         * -> used for tracing sporadic tasks. */
+        lt_t    last_suspension;
+#endif
+};
+
+struct pfair_param;
+
+/*      RT task parameters for scheduling extensions
+ *      These parameters are inherited during clone and therefore must
+ *      be explicitly set up before the task set is launched.
+ */
+struct rt_param {
+        /* Generic flags available for plugin-internal use. */
+        unsigned int            flags:8;
+
+        /* do we need to check for srp blocking? */
+        unsigned int            srp_non_recurse:1;
+
+        /* is the task present? (true if it can be scheduled) */
+        unsigned int            present:1;
+
+        /* has the task completed? */
+        unsigned int            completed:1;
+
+#ifdef CONFIG_LITMUS_LOCKING
+        /* Is the task being priority-boosted by a locking protocol? */
+        unsigned int            priority_boosted:1;
+        /* If so, when did this start? */
+        lt_t                    boost_start_time;
+
+        /* How many LITMUS^RT locks does the task currently hold/wait for? */
+        unsigned int            num_locks_held;
+        /* How many PCP/SRP locks does the task currently hold/wait for? */
+        unsigned int            num_local_locks_held;
+#endif
+
+        /* user controlled parameters */
+        struct rt_task          task_params;
+
+        /* timing parameters */
+        struct rt_job           job_params;
+
+        /* Should the next job be released at some time other than
+         * just period time units after the last release?
+         */
+        unsigned int            sporadic_release:1;
+        lt_t                    sporadic_release_time;
+
+
+        /* task representing the current "inherited" task
+         * priority, assigned by inherit_priority and
+         * return priority in the scheduler plugins.
+         * could point to self if PI does not result in
+         * an increased task priority.
+         */
+         struct task_struct*    inh_task;
+
+#ifdef CONFIG_NP_SECTION
+        /* For the FMLP under PSN-EDF, it is required to make the task
+         * non-preemptive from kernel space. In order not to interfere with
+         * user space, this counter indicates the kernel space np setting.
+         * kernel_np > 0 => task is non-preemptive
+         */
+        unsigned int    kernel_np;
+#endif
+
+        /* This field can be used by plugins to store where the task
+         * is currently scheduled. It is the responsibility of the
+         * plugin to avoid race conditions.
+         *
+         * This used by GSN-EDF and PFAIR.
+         */
+        volatile int            scheduled_on;
+
+        /* Is the stack of the task currently in use? This is updated by
+         * the LITMUS core.
+         *
+         * Be careful to avoid deadlocks!
+         */
+        volatile int            stack_in_use;
+
+        /* This field can be used by plugins to store where the task
+         * is currently linked. It is the responsibility of the plugin
+         * to avoid race conditions.
+         *
+         * Used by GSN-EDF.
+         */
+        volatile int            linked_on;
+
+        /* PFAIR/PD^2 state. Allocated on demand. */
+        struct pfair_param*     pfair;
+
+        /* Fields saved before BE->RT transition.
+         */
+        int old_policy;
+        int old_prio;
+
+        /* ready queue for this task */
+        struct _rt_domain* domain;
+
+        /* heap element for this task
+         *
+         * Warning: Don't statically allocate this node. The heap
+         *          implementation swaps these between tasks, thus after
+         *          dequeuing from a heap you may end up with a different node
+         *          then the one you had when enqueuing the task.  For the same
+         *          reason, don't obtain and store references to this node
+         *          other than this pointer (which is updated by the heap
+         *          implementation).
+         */
+        struct bheap_node*      heap_node;
+        struct release_heap*    rel_heap;
+
+        /* Used by rt_domain to queue task in release list.
+         */
+        struct list_head list;
+
+        /* Pointer to the page shared between userspace and kernel. */
+        struct control_page * ctrl_page;
+};
+
+#endif
+
+#endif