On Fri, Oct 11, 2013 at 04:55:31PM +0800, Wenchao Xia wrote:
+/* Recursive FIFO lock
+ *
+ * This lock provides more features than a plain mutex:
+ *
+ * 1. Fairness - enforces FIFO order.
+ * 2. Nesting - can be taken recursively.
+ * 3. Contention callback - optional, called when thread must wait.
+ *
+ * The recursive FIFO lock is heavyweight so prefer other synchronization
+ * primitives if you do not need its features.
+ */
+typedef struct {
+ QemuMutex lock; /* protects all fields */
+
+ /* FIFO order */
+ unsigned int head; /* active ticket number */
+ unsigned int tail; /* waiting ticket number */
+ QemuCond cond; /* used to wait for our ticket number */
+
+ /* Nesting */
+ QemuThread owner_thread; /* thread that currently has ownership */
+ unsigned int nesting; /* amount of nesting levels */
+
+ /* Contention callback */
+ void (*cb)(void *); /* called when thread must wait, with ->lock
+ * held so it may not recursively lock/unlock
+ */
+ void *cb_opaque;
+} RFifoLock;
+
If you respin, the define can be moved to util/rfifolock.c, leave
typedef struct RFifoLock RFifoLock;
in header.
Then the struct cannot be embedded as a field, it would require heap
allocation of all RFifoLocks.
This is why I chose to include the definition in the header file.
Stefan