Merge branch 'embb540_spinlock_yield' into development

base_c/include/embb/base/c/mutex.h

@@ -179,6 +179,9 @@ int embb_spin_init(
 /**
  * Spins until the spinlock can be locked and locks it.
  *
+ * \note This method yields the current thread in regular,
+ *       implementation-defined intervals.
+ *
  * \pre \c spinlock is initialized \n
  * \post If successful, \c spinlock is locked.
  * \return EMBB_SUCCESS if spinlock could be locked. \n

base_c/src/mutex.c

@@ -25,6 +25,7 @@
  */
 
 #include <embb/base/c/mutex.h>
+#include <embb/base/c/thread.h>
 #include <assert.h>
 
 #include <embb/base/c/internal/unused.h>
@@ -125,10 +126,15 @@ int embb_spin_init(embb_spinlock_t* spinlock) {
 
 int embb_spin_lock(embb_spinlock_t* spinlock) {
   int expected = 0;
+  int spins = 1;
 
   // try to swap the
   while (0 == embb_atomic_compare_and_swap_int(
     &spinlock->atomic_spin_variable_, &expected, 1)) {
+    if (0 == (spins & 1023)) {
+      embb_thread_yield();
+    }
+    spins++;
     // reset expected, as CAS might change it...
     expected = 0;
   }

base_cpp/include/embb/base/mutex.h

@@ -192,6 +192,9 @@ class Spinlock {
   /**
    * Waits until the spinlock can be locked and locks it.
    *
+   * \note This method yields the current thread in regular,
+   *       implementation-defined intervals.
+   *
    * \pre The spinlock is not locked by the current thread.
    * \post The spinlock is locked.
    * \threadsafe