Changeset d54b303 in mainline for uspace/lib/c/include/futex.h

Timestamp:

2012-12-04T05:18:19Z (12 years ago)

Author:

Adam Hraska <adam.hraska+hos@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

32d2e60

Parents:

9a3b469

Message:

Initial version of nop futexes that are upgradable to proper futexes.

File:

• uspace/lib/c/include/futex.h (modified) (2 diffs)

uspace/lib/c/include/futex.h

@@ -40 +40 @@
 #include <libc.h>
 
-#define FUTEX_INITIALIZE(val) {{(val)}}
-#define FUTEX_INITIALIZER     FUTEX_INITIALIZE(1)
-
 typedef struct futex {
         atomic_t val;
+#ifdef FUTEX_UPGRADABLE
+        int upgraded;
+#endif
 } futex_t;
 
@@ -50 +50 @@
 extern void futex_initialize(futex_t *futex, int value);
 
+#ifdef FUTEX_UPGRADABLE
+#include <rcu.h>
+
+#define FUTEX_INITIALIZE(val) {{(val)}, {0}}
+
+#define futex_down(fut) \
+({ \
+        rcu_read_lock(); \
+        (fut)->upgraded = rcu_access(_upgrade_futexes); \
+        if ((fut)->upgraded) \
+                (void) _futex_down((fut)); \
+})
+
+#define futex_trydown(fut) \
+({ \
+        rcu_read_lock(); \
+        int _upgraded = rcu_access(_upgrade_futexes); \
+        if (_upgraded) { \
+                int _acquired = _futex_trydown((fut)); \
+                if (!_acquired) { \
+                        rcu_read_unlock(); \
+                } else { \
+                        (fut)->upgraded = true; \
+                } \
+                _acquired; \
+        } else { \
+                (fut)->upgraded = false; \
+                1; \
+        } \
+})
+                
+#define futex_up(fut) \
+({ \
+        if ((fut)->upgraded) \
+                (void) _futex_up((fut)); \
+        rcu_read_unlock(); \
+})
+
+extern int _upgrade_futexes;
+
+extern void futex_upgrade_all_and_wait(void);
+                
+#else
+
+#define FUTEX_INITIALIZE(val) {{(val)}}
+
 #define futex_down(fut)     (void)_futex_down((fut))
 #define futex_trydown(fut)  _futex_trydown((fut))
 #define futex_up(fut)       (void)_futex_up((fut))
+                
+#endif
 
+#define FUTEX_INITIALIZER     FUTEX_INITIALIZE(1)
 
 /** Try to down the futex.