Added support for simple binary semaphores in addition to the high

power binary/mutex style semaphores already supported by RTEMS.  This
was done at the request of Eric Norum <eric@cls.usask.ca> in support
of his effort to port EPICS to RTEMS.  This change consisted of
changing the nesting_allowed boolean into a lock_nesting_behavior
enumerated value as well as allowing the core mutex object to optionally
support ensuring that the holder of a binary semaphore released it.
Finally, a more subtle enhancement was to allow the non-holder to release
a priority inheritance/ceiling mutex and still allow the holding task
to return to its original priority.

1 files changed, 33 insertions, 3 deletions

diff --git a/cpukit/score/include/rtems/score/coremutex.h b/cpukit/score/include/rtems/score/coremutex.h
index 73f92c76e0..32e4f40b5e 100644
--- a/cpukit/score/include/rtems/score/coremutex.h
+++ b/cpukit/score/include/rtems/score/coremutex.h
@@ -63,6 +63,35 @@ typedef enum {
 }   CORE_mutex_Status;
 
 /*
+ *  Mutex lock nesting behavior
+ *
+ *  CORE_MUTEX_NESTING_ACQUIRES:
+ *    This sequence has no blocking or errors:
+ *         lock(m)
+ *         lock(m)
+ *         unlock(m)
+ *         unlock(m)
+ *
+ *  CORE_MUTEX_NESTING_IS_ERROR
+ *    This sequence returns an error at the indicated point:
+ *        lock(m)
+ *        lock(m)   - already locked error
+ *        unlock(m)
+ *
+ *  CORE_MUTEX_NESTING_BLOCKS
+ *    This sequence performs as indicated:
+ *        lock(m)
+ *        lock(m)   - deadlocks or timeouts
+ *        unlock(m) - releases
+ */
+
+typedef enum {
+  CORE_MUTEX_NESTING_ACQUIRES,
+  CORE_MUTEX_NESTING_IS_ERROR,
+  CORE_MUTEX_NESTING_BLOCKS
+}  CORE_mutex_Nesting_behaviors;
+ 
+/*
  *  Locked and unlocked values
  */
 
@@ -75,9 +104,10 @@ typedef enum {
  */
 
 typedef struct {
-  boolean                 allow_nesting;
-  CORE_mutex_Disciplines  discipline;
-  Priority_Control        priority_ceiling;
+  CORE_mutex_Nesting_behaviors lock_nesting_behavior;
+  boolean                      only_owner_release;
+  CORE_mutex_Disciplines       discipline;
+  Priority_Control             priority_ceiling;
 }   CORE_mutex_Attributes;
  
 /*