Changeset 178 for soft/giet_vm/libs/spin_lock.c

Timestamp:

Jul 22, 2012, 12:06:11 PM (12 years ago)

Author:

karaoui

Message:

updating libs.

File:

• soft/giet_vm/libs/spin_lock.c (modified) (2 diffs)

soft/giet_vm/libs/spin_lock.c

@@ -10 +10 @@
 // It is a simple binary lock, without waiting queue.
 // 
-// The lock_acquire() and lock_release() functions do not require a system call.
-// The barrier itself must have been allocated in a non cacheable segment,
-// if the platform does not provide hardwate cache coherence.
+// The lock_acquire(), lock_try_acquire() and lock_release() functions do 
+// not require a system call.
 //
 // ALL locks must be defined in the mapping_info data structure, 
 // to be initialised by the GIET in the boot phase.
 // The vobj_get_vbase() system call (defined in stdio.c and stdio.h files)
-// can be used to get the virtual base address of the lock fro it's name.
+// can be used to get the virtual base address of the lock from it's name.
 ///////////////////////////////////////////////////////////////////////////////////
 
@@ -65 +64 @@
 }
 
+//////////////////////////////////////////////////////////////////////////////
+// lock_try_acquire()
+//////////////////////////////////////////////////////////////////////////////
+int lock_try_acquire( giet_lock_t* lock )
+{
+        register int ret = 0;   
+    register unsigned int*      plock = &lock->value;
+
+        asm volatile ("ll   $2,    0(%1)                    \n" // $2 <= _locks_lock
+                  "bnez $2,    _lock_done           \n" // exitif busy
+                  "li   $3,    1                            \n" // prepare argument for sc  
+                  "sc   $3,    0(%1)                \n" // try to set _locks_busy
+                  "xori %0, $3, 1                   \n" // ret = !$3
+                  "_lock_done:                          \n"
+                  :"=r"(ret)
+                  :"r"(plock)
+                  :"$2","$3");
+    return ret;
+}