Export IRQ count to control page

Also add some compile-time checks to detect unexpected offsets.

5 files changed, 38 insertions, 18 deletions

diff --git a/include/litmus/rt_param.h b/include/litmus/rt_param.h
index 6456ed04fddb..8d9aa07cf324 100644
--- a/include/litmus/rt_param.h
+++ b/include/litmus/rt_param.h
@@ -65,12 +65,12 @@ struct rt_task {
 };
 
 union np_flag {
-        uint32_t raw;
+        uint64_t raw;
         struct {
                 /* Is the task currently in a non-preemptive section? */
-                uint32_t flag:31;
+                uint64_t flag:31;
                 /* Should the task call into the scheduler? */
-                uint32_t preempt:1;
+                uint64_t preempt:1;
         } np;
 };
 
@@ -93,13 +93,25 @@ struct control_page {
          * 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
-         * prior to starting the system call. */
-        uint64_t ts_syscall_start; /* Feather-Trace cycles */
+         * 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__
 
diff --git a/include/litmus/trace_irq.h b/include/litmus/trace_irq.h
index 01e4b98fc3e0..0d0c042ba9c3 100644
--- a/include/litmus/trace_irq.h
+++ b/include/litmus/trace_irq.h
@@ -3,17 +3,7 @@
 
 #ifdef CONFIG_SCHED_OVERHEAD_TRACE
 
-#include <asm/atomic.h>
-#include <linux/percpu.h>
-
-extern DEFINE_PER_CPU(atomic_t, irq_fired_count);
-
-static inline void ft_irq_fired(void)
-{
-        /* Only called with preemptions disabled.  */
-        atomic_inc(&__get_cpu_var(irq_fired_count));
-}
-
+void ft_irq_fired(void);
 
 #else
 
diff --git a/litmus/ctrldev.c b/litmus/ctrldev.c
index 9969ab17c190..41919b2714cb 100644
--- a/litmus/ctrldev.c
+++ b/litmus/ctrldev.c
@@ -133,6 +133,17 @@ static int __init init_litmus_ctrl_dev(void)
 
         BUILD_BUG_ON(sizeof(struct control_page) > PAGE_SIZE);
 
+        BUILD_BUG_ON(sizeof(union np_flag) != sizeof(uint64_t));
+
+        BUILD_BUG_ON(offsetof(struct control_page, sched.raw)
+                     != LITMUS_CP_OFFSET_SCHED);
+        BUILD_BUG_ON(offsetof(struct control_page, irq_count)
+                     != LITMUS_CP_OFFSET_IRQ_COUNT);
+        BUILD_BUG_ON(offsetof(struct control_page, ts_syscall_start)
+                     != LITMUS_CP_OFFSET_TS_SC_START);
+        BUILD_BUG_ON(offsetof(struct control_page, irq_syscall_start)
+                     != LITMUS_CP_OFFSET_IRQ_SC_START);
+
         printk("Initializing LITMUS^RT control device.\n");
         err = misc_register(&litmus_ctrl_dev);
         if (err)
diff --git a/litmus/litmus.c b/litmus/litmus.c
index 81384327e850..c842de46587b 100644
--- a/litmus/litmus.c
+++ b/litmus/litmus.c
@@ -536,8 +536,6 @@ static int __init _init_litmus(void)
          */
         printk("Starting LITMUS^RT kernel\n");
 
-        BUILD_BUG_ON(sizeof(union np_flag) != sizeof(uint32_t));
-
         register_sched_plugin(&linux_sched_plugin);
 
         bheap_node_cache    = KMEM_CACHE(bheap_node, SLAB_PANIC);
diff --git a/litmus/trace.c b/litmus/trace.c
index fc1d03f35d39..c511003ea911 100644
--- a/litmus/trace.c
+++ b/litmus/trace.c
@@ -18,6 +18,15 @@ static unsigned int ts_seq_no = 0;
 
 DEFINE_PER_CPU(atomic_t, irq_fired_count);
 
+void ft_irq_fired(void)
+{
+        /* Only called with preemptions disabled.  */
+        atomic_inc(&__get_cpu_var(irq_fired_count));
+
+        if (has_control_page(current))
+                get_control_page(current)->irq_count++;
+}
+
 static inline void clear_irq_fired(void)
 {
         atomic_set(&__raw_get_cpu_var(irq_fired_count), 0);