Remove heap allocation of xscom mutex.

Since mutexes are simply a uint64 with a static initializer, the xscom mutex
is now a instance variable directly in the cpu object.

Remove unneeded mutex_create function and changed the behavior of
mutex_destroy.

Change-Id: If6e1d1bf0083c32ef9e7502d27678811bdaf7e1e
Reviewed-on: http://gfw160.austin.ibm.com:8080/gerrit/150
Tested-by: Jenkins Server
Reviewed-by: Douglas R. Gilbert <dgilbert@us.ibm.com>
Reviewed-by: Thi N. Tran <thi@us.ibm.com>

5 files changed, 12 insertions, 45 deletions

diff --git a/src/include/kernel/cpu.H b/src/include/kernel/cpu.H
index 0f36dd941..8f6fedb69 100644
--- a/src/include/kernel/cpu.H
+++ b/src/include/kernel/cpu.H
@@ -36,7 +36,7 @@ struct cpu_t
     task_t* idle_task;
 
         /** XSCOM mutex to serialize access per CPU */
-    mutex_t * xscom_mutex;
+    mutex_t xscom_mutex;
 };
 
 /** @fn getCpuId
diff --git a/src/include/sys/sync.h b/src/include/sys/sync.h
index 68b570aec..b6274a0a6 100644
--- a/src/include/sys/sync.h
+++ b/src/include/sys/sync.h
@@ -51,12 +51,6 @@ void barrier_destroy (barrier_t * i_barrier);
 void barrier_wait (barrier_t * i_barrier);
 
 /**
- * Create a mutex and initialize a mutex
- * @returns a pointer to the mutex
- */
-mutex_t * mutex_create();
-
-/**
  * Initialize a mutex object
  * @param[out] o_mutex the mutex
  * @pre an uninitialized mutex object
@@ -65,11 +59,12 @@ mutex_t * mutex_create();
 void mutex_init(mutex_t * o_mutex);
 
 /**
- * Destroy a mutex
- * @param[in/out] i_mutex The mutex
- * @pre mutex must have been created with mutex_create()
+ * Destroy / Uninitialize a mutex object.
+ * @param[in] i_mutex The mutex
+ * @note This does not free the memory associated with the object if the mutex
+ *       was allocated off the heap.
  */
-void mutex_destroy(mutex_t *& io_mutex);
+void mutex_destroy(mutex_t * i_mutex);
 
 /**
  * Obtain a lock on a mutex
diff --git a/src/kernel/cpumgr.C b/src/kernel/cpumgr.C
index 844f8c44a..27417ef0d 100644
--- a/src/kernel/cpumgr.C
+++ b/src/kernel/cpumgr.C
@@ -8,6 +8,7 @@
 #include <util/singleton.H>
 #include <arch/ppc.H>
 #include <kernel/timemgr.H>
+#include <sys/sync.h>
 
 cpu_t* CpuManager::cv_cpus[CpuManager::MAXCPUS] = { NULL };
 
@@ -58,7 +59,7 @@ void CpuManager::startCPU(ssize_t i)
         cpu->scheduler_extra = NULL;
 	cpu->kernel_stack = 
 	    (void*) (((uint64_t)PageManager::allocatePage(4)) + 16320);
-        cpu->xscom_mutex = NULL;
+        cpu->xscom_mutex = (mutex_t)MUTEX_INITIALIZER;
 	
 	// Create idle task.
 	cpu->idle_task = TaskManager::createIdleTask();
diff --git a/src/lib/sync.C b/src/lib/sync.C
index a70761eef..093c7f41e 100644
--- a/src/lib/sync.C
+++ b/src/lib/sync.C
@@ -66,15 +66,6 @@ void barrier_wait (barrier_t * i_barrier)
 
 //-----------------------------------------------------------------------------
 
-mutex_t * mutex_create()
-{
-    mutex_t * m = new mutex_t;
-    mutex_init(m);
-    return m;
-}
-
-//-----------------------------------------------------------------------------
-
 void mutex_init(mutex_t * o_mutex)
 {
     o_mutex->iv_val = 0;
@@ -85,8 +76,7 @@ void mutex_init(mutex_t * o_mutex)
 
 void mutex_destroy(mutex_t *& i_mutex)
 {
-    delete i_mutex;
-    i_mutex = NULL;
+    i_mutex->iv_val = ~0;
     return;
 }
 
diff --git a/src/lib/syscall_mmio.C b/src/lib/syscall_mmio.C
index 91e4e113b..83a4f8f82 100644
--- a/src/lib/syscall_mmio.C
+++ b/src/lib/syscall_mmio.C
@@ -34,26 +34,7 @@ mutex_t * mmio_xscom_mutex()
 
     // Ensure task is pinned.
     assert(task->affinity_pinned);
-
-    // Get mutex from cpu structure.
-    mutex_t * mutex = task->cpu->xscom_mutex;
-
-    // Create mutex if not created.
-    if (NULL == mutex)
-    {
-        mutex = mutex_create();
-
-        // Atomically update xscom_mutex with new mutex.
-        if (!__sync_bool_compare_and_swap(&task->cpu->xscom_mutex, NULL, mutex))
-        {
-            // Failed, some other thread beat us to it.
-
-            // Destroy mutex and get one created by other thread in the
-            // meantime.
-            mutex_destroy(mutex);
-            mutex = task->cpu->xscom_mutex;
-        }
-    }
-
-    return mutex;
+    
+    // Return mutex from cpu structure.
+    return &task->cpu->xscom_mutex;
 }