MT#62181 wheeltimer: support absolute expiry

Move determination of absolute expiry time up into insert_timer(), and
make the rest of the code operate on absolute time. Add an extra method
to directly support absolute time.

Change-Id: I0a8dd27d82fb69b5083a6cfab693bfb275738495

core/sip/wheeltimer.cpp

@@ -46,9 +46,14 @@ timer::~timer()
 }
 
 void _wheeltimer::insert_timer(timer* t, uint64_t relative_us)
+{
+    insert_timer_abs(t, (gettimeofday_us() + relative_us));
+}
+
+void _wheeltimer::insert_timer_abs(timer* t, uint64_t us)
 {
     std::lock_guard<std::mutex> lock(buckets_mut);
-    place_timer(t, relative_us);
+    place_timer(t, us);
     // Wake up worker thread: The new timer might be the next one to run
     buckets_cond.notify_one();
 }
@@ -144,9 +149,9 @@ uint64_t _wheeltimer::get_timer_bucket(timer* t)
     return bucket;
 }
 
-void _wheeltimer::place_timer(timer* t, uint64_t relative_us)
+void _wheeltimer::place_timer(timer* t, uint64_t us)
 {
-    t->arm(relative_us);
+    t->arm(us);
     uint64_t bucket = get_timer_bucket(t);
     add_timer_to_bucket(t, bucket);
 }

core/sip/wheeltimer.h

@@ -72,11 +72,11 @@ public:
     }
 
 private:
-    void arm(uint64_t relative)
+    void arm(uint64_t us)
     {
 	if (expires)
 	    return;
-	expires = relative + gettimeofday_us();
+	expires = us;
     }
 
     void link(timer_list& new_list)
@@ -159,6 +159,7 @@ public:
     }
 
     void insert_timer(timer* t, uint64_t relative_expiry_us);
+    void insert_timer_abs(timer* t, uint64_t expiry_us);
     void remove_timer(timer* t);
 };