1 files changed, 19 insertions, 4 deletions

diff --git a/include/litmus.h b/include/litmus.h
index 94e4b6a..06f84bb 100644
--- a/include/litmus.h
+++ b/include/litmus.h
@@ -104,14 +104,29 @@ int sleep_next_period(void);
 
 /* interruptible critical section support */
 #define MAX_ICS_NESTING         16
-#define ICS_END_OF_STACK        (-2)
+#define ICS_STACK_EMPTY         (-1)
+
+struct ics_descriptor {
+        /* ICS id, only read by kernel */
+        int     id;
+        /* rollback program counter, only read by kernel */
+        void*   pc; 
+        /* rollback stack pointer, not used by kernel */
+        void*    sp;
+        /* retry flag, not used by kernel */
+        int*    retry;
+};
 
 /* ICS control block */
 struct ics_cb {
-        void*           rollback_eip;
-        void*           rollback_esp;
-        int             ics_stack[MAX_ICS_NESTING];
+        /* Points to the top-most valid entry.
+         * -1 indicates an empty stack.
+         * Read and written by kernel.
+         */
+        int                     top;    
+        struct ics_descriptor   ics_stack[MAX_ICS_NESTING];
 };
+
 int reg_ics_cb(struct ics_cb* ics_cb);
 int start_wcs(int od);