Since we are moving from semaphores to mutex, there should be a
mutex_rw. I had a try
at creating one (might as well convert from sem_rw). I'll bet somebody
here can do a
lot better, but this will do if need be.
--- linux-2.6.16.1-stock/include/linux/mutex_rw.h 1969-12-31
16:00:00.000000000 -0800
+++ linux-2.6.16.1-nvl/include/linux/mutex_rw.h 2006-04-04
18:11:56.000000000 -0700
@@ -0,0 +1,60 @@
+/* Linux RW mutex
+ * This file: GNU GPL v2 or later, Joshua Hudson <[email protected]>
+ *
+ * Somebody else can make this fast. I just made this work.
+ *
+ * DANGER! Change of this file will break module binaries if any
+ * rw mutex is shared between main kernel and modules or between
+ * modules with a different version.
+ */
+
+#ifndef __KERNEL_MUTEX_RW
+#define __KERNEL_MUTEX_RW
+#ifdef __KERNEL__
+
+#include <linux/mutex.h>
+
+struct rw_mutex {
+ struct mutex r_mutex;
+ struct mutex w_mutex;
+ unsigned n_readers;
+};
+
+static inline void rw_mutex_init(struct rw_mutex *rw)
+{
+ mutex_init(&rw->r_mutex);
+ mutex_init(&rw->w_mutex);
+ rw->n_readers = 0;
+}
+
+static inline void rw_mutex_destroy(struct rw_mutex *rw)
+{
+ mutex_destroy(&rw->r_mutex);
+ mutex_destroy(&rw->w_mutex);
+}
+
+static inline void mutex_lock_w(struct rw_mutex *rw)
+{
+ mutex_lock(&rw->w_mutex);
+}
+
+static inline void mutex_unlock_w(struct rw_mutex *rw)
+{
+ mutex_unlock(&rw->w_mutex);
+}
+
+static inline void mutex_lock_r(struct rw_mutex *rw)
+{
+ mutex_lock(&rw->r_mutex);
+ if (++rw->n_readers == 1)
+ mutex_lock(&rw->w_mutex);
+ mutex_unlock(&rw->r_mutex);
+}
+
+static inline void mutex_unlock_r(struct rw_mutex *rw)
+{
+ mutex_lock(&rw->r_mutex);
+ if (--rw->n_readers == 0)
+ mutex_unlock(&rw->w_mutex);
+ mutex_unlock(&rw->r_mutex);
+}
+
+#endif
+#endif
-
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