Second Extended Filesystem (ext2) and other improvements (#33)

[lunaix-os.git] / lunaix-os / includes / lunaix / switch.h

diff --git a/lunaix-os/includes/lunaix/switch.h b/lunaix-os/includes/lunaix/switch.h
new file mode 100644 (file)
index 0000000..4daca4d
--- /dev/null
+++ b/lunaix-os/includes/lunaix/switch.h
@@ -0,0 +1,60 @@
+#ifndef __LUNAIX_SWITCH_H
+#define __LUNAIX_SWITCH_H
+
+#define SWITCH_MODE_NORMAL   0
+#define SWITCH_MODE_FAST     1
+#define SWITCH_MODE_GIVEUP   2
+
+#ifndef __ASM__
+
+#include <lunaix/types.h>
+
+struct signpost_result
+{
+    int mode;
+    ptr_t stack;
+};
+
+/**
+ * @brief Decide how current thread should perform the context switch
+ *        back to it's previously saved context. 
+ * 
+ *        Return a user stack pointer perform a temporary fast redirected 
+ *        context switch. 
+ *        No redirection is required if such pointer is null.
+ * 
+ *        This function might never return if the decision is made to give up
+ *        this switching.
+ * 
+ *        NOTE: This function might have side effects, it can only be
+ *         called within the twilight zone of context restore. (after entering
+ *         do_switch and before returning from exception)
+ * 
+ * @return ptr_t
+ */
+ptr_t
+switch_signposting();
+
+static inline void
+redirect_switch(struct signpost_result* res, ptr_t stack)
+{
+    res->mode  = SWITCH_MODE_FAST;
+    res->stack = stack;
+}
+
+static inline void
+continue_switch(struct signpost_result* res)
+{
+    res->mode  = SWITCH_MODE_NORMAL;
+    res->stack = 0;
+}
+
+static inline void
+giveup_switch(struct signpost_result* res)
+{
+    res->mode  = SWITCH_MODE_GIVEUP;
+    res->stack = 0;
+}
+
+#endif
+#endif /* __LUNAIX_SWITCH_H */