Changes in uspace/lib/c/include/fibril_synch.h [f787c8e:2965d18] in mainline

File:

• uspace/lib/c/include/fibril_synch.h (modified) (4 diffs)

uspace/lib/c/include/fibril_synch.h

@@ -41 +41 @@
 #include <sys/time.h>
 #include <stdbool.h>
+#include <futex.h>
+
+/**
+ * "Restricted" fibril mutex.
+ *
+ * Similar to `fibril_mutex_t`, but has a set of restrictions placed on its
+ * use. Within a rmutex critical section, you
+ *         - may not use any other synchronization primitive,
+ *           save for another `fibril_rmutex_t`. This includes nonblocking
+ *           operations like cvar signal and mutex unlock.
+ *         - may not read IPC messages
+ *         - may not start a new thread/fibril
+ *           (creating fibril without starting is fine)
+ *
+ * Additionally, locking with a timeout is not possible on this mutex,
+ * and there is no associated condition variable type.
+ * This is a design constraint, not a lack of implementation effort.
+ */
+typedef struct {
+        // TODO: At this point, this is just silly handwaving to hide current
+        //       futex use behind a fibril based abstraction. Later, the imple-
+        //       mentation will change, but the restrictions placed on this type
+        //       will allow it to be simpler and faster than a regular mutex.
+        //       There might also be optional debug checking of the assumptions.
+        //
+        //       Note that a consequence of the restrictions is that if we are
+        //       running on a single thread, no other fibril can ever get to run
+        //       while a fibril has a rmutex locked. That means that for
+        //       single-threaded programs, we can reduce all rmutex locks and
+        //       unlocks to simple branches on a global bool variable.
+
+        futex_t futex;
+} fibril_rmutex_t;
+
+#define FIBRIL_RMUTEX_INITIALIZER(name) \
+        { .futex = FUTEX_INITIALIZE(1) }
+
+#define FIBRIL_RMUTEX_INITIALIZE(name) \
+        fibril_rmutex_t name = FIBRIL_RMUTEX_INITIALIZER(name)
 
 typedef struct {
@@ -147 +186 @@
         long int count;
         list_t waiters;
-        bool closed;
 } fibril_semaphore_t;
 
@@ -163 +201 @@
 #define FIBRIL_SEMAPHORE_INITIALIZE(name, cnt) \
         fibril_semaphore_t name = FIBRIL_SEMAPHORE_INITIALIZER(name, cnt)
+
+extern void fibril_rmutex_initialize(fibril_rmutex_t *);
+extern void fibril_rmutex_lock(fibril_rmutex_t *);
+extern bool fibril_rmutex_trylock(fibril_rmutex_t *);
+extern void fibril_rmutex_unlock(fibril_rmutex_t *);
 
 extern void fibril_mutex_initialize(fibril_mutex_t *);
@@ -198 +241 @@
 extern void fibril_semaphore_up(fibril_semaphore_t *);
 extern void fibril_semaphore_down(fibril_semaphore_t *);
-extern errno_t fibril_semaphore_down_timeout(fibril_semaphore_t *, suseconds_t);
-extern void fibril_semaphore_close(fibril_semaphore_t *);
-
-typedef struct mpsc mpsc_t;
-extern mpsc_t *mpsc_create(size_t);
-extern void mpsc_destroy(mpsc_t *);
-extern errno_t mpsc_send(mpsc_t *, const void *);
-extern errno_t mpsc_receive(mpsc_t *, void *, const struct timeval *);
-extern void mpsc_close(mpsc_t *);
 
 #endif