diff --git a/include/sc.hpp b/include/sc.hpp
index b849a1f..b480050 100644
--- a/include/sc.hpp
+++ b/include/sc.hpp
@@ -54,7 +54,7 @@ class Sc : public Kobject, public Refcount
 
         static unsigned prio_top CPULOCAL;
 
-        void ready_enqueue (uint64);
+        void ready_enqueue (uint64, bool use_left = true);
         void ready_dequeue (uint64);
 
         static void free (Rcu_elem * a) {
@@ -90,7 +90,7 @@ class Sc : public Kobject, public Refcount
         static void rke_handler();
 
         NORETURN
-        static void schedule (bool = false);
+        static void schedule (bool = false, bool = true);
 
         ALWAYS_INLINE
         static inline void *operator new (size_t) { return cache.alloc(); }
diff --git a/include/syscall.hpp b/include/syscall.hpp
index 59e4489..5d61f1e 100644
--- a/include/syscall.hpp
+++ b/include/syscall.hpp
@@ -138,6 +138,9 @@ class Sys_ec_ctrl : public Sys_regs
     public:
         ALWAYS_INLINE
         inline unsigned long ec() const { return ARG_1 >> 8; }
+
+        ALWAYS_INLINE
+        inline unsigned op() const { return flags() & 0x3; }
 };
 
 class Sys_sc_ctrl : public Sys_regs
diff --git a/src/sc.cpp b/src/sc.cpp
index 53ff07b..bc4dfa2 100644
--- a/src/sc.cpp
+++ b/src/sc.cpp
@@ -52,7 +52,7 @@ Sc::Sc (Pd *own, Ec *e, unsigned c, Sc *x) : Kobject (SC, static_cast<Space_obj
     trace (TRACE_SYSCALL, "SC:%p created (EC:%p CPU:%#x P:%#x Q:%#x) - xCPU", this, e, c, prio, budget / (Lapic::freq_bus / 1000));
 }
 
-void Sc::ready_enqueue (uint64 t)
+void Sc::ready_enqueue (uint64 t, bool use_left)
 {
     assert (prio < priorities);
     assert (cpu == Cpu::id);
@@ -68,13 +68,13 @@ void Sc::ready_enqueue (uint64 t)
         next = list[prio];
         prev = list[prio]->prev;
         next->prev = prev->next = this;
-        if (left)
+        if (use_left && left)
             list[prio] = this;
     }
 
     trace (TRACE_SCHEDULE, "ENQ:%p (%02u) PRIO:%#x TOP:%#x %s", this, left, prio, prio_top, prio > current->prio ? "reschedule" : "");
 
-    if (prio > current->prio || (this != current && prio == current->prio && left))
+    if (prio > current->prio || (this != current && prio == current->prio && (use_left && left)))
         Cpu::hazard |= HZD_SCHED;
 
     if (!left)
@@ -106,7 +106,7 @@ void Sc::ready_dequeue (uint64 t)
     tsc = t;
 }
 
-void Sc::schedule (bool suspend)
+void Sc::schedule (bool suspend, bool use_left)
 {
     Counter::print<1,16> (++Counter::schedule, Console_vga::COLOR_LIGHT_CYAN, SPN_SCH);
 
@@ -123,7 +123,7 @@ void Sc::schedule (bool suspend)
         delete current;
     else
     if (EXPECT_TRUE (!suspend))
-        current->ready_enqueue (t);
+        current->ready_enqueue (t, use_left);
 
     Sc *sc = list[prio_top];
     assert (sc);
diff --git a/src/syscall.cpp b/src/syscall.cpp
index 975d4dc..6e792b0 100644
--- a/src/syscall.cpp
+++ b/src/syscall.cpp
@@ -409,6 +412,9 @@ void Ec::sys_ec_ctrl()
 {
     Sys_ec_ctrl *r = static_cast<Sys_ec_ctrl *>(current->sys_regs());
 
+    switch (r->op()) {
+        case 0:
+{
     Capability cap = Space_obj::lookup (r->ec());
     if (EXPECT_FALSE (cap.obj()->type() != Kobject::EC || !(cap.prm() & 1UL << 0))) {
         trace (TRACE_ERROR, "%s: Bad EC CAP (%#lx)", __func__, r->ec());
@@ -423,6 +429,18 @@ void Ec::sys_ec_ctrl()
 
         if (Cpu::id != ec->cpu && Ec::remote (ec->cpu) == ec)
             Lapic::send_ipi (ec->cpu, VEC_IPI_RKE);
+
+    }
+}
+            break;
+
+        case 1:
+            current->cont = sys_finish<Sys_regs::SUCCESS>;
+            Sc::schedule (false, false);
+            break;
+
+        default:
+      	     sys_finish<Sys_regs::BAD_PAR>();
     }
 
     sys_finish<Sys_regs::SUCCESS>();