1 files changed, 71 insertions, 0 deletions

diff --git a/include/asm-i386/rwlock.h b/include/asm-i386/rwlock.h
new file mode 100644
index 000000000000..b57cc7afdf7e
--- /dev/null
+++ b/include/asm-i386/rwlock.h
@@ -0,0 +1,71 @@
+/* include/asm-i386/rwlock.h
+ *
+ *      Helpers used by both rw spinlocks and rw semaphores.
+ *
+ *      Based in part on code from semaphore.h and
+ *      spinlock.h Copyright 1996 Linus Torvalds.
+ *
+ *      Copyright 1999 Red Hat, Inc.
+ *
+ *      Written by Benjamin LaHaise.
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ */
+#ifndef _ASM_I386_RWLOCK_H
+#define _ASM_I386_RWLOCK_H
+
+#define RW_LOCK_BIAS             0x01000000
+#define RW_LOCK_BIAS_STR        "0x01000000"
+
+#define __build_read_lock_ptr(rw, helper)   \
+        asm volatile(LOCK "subl $1,(%0)\n\t" \
+                     "jns 1f\n" \
+                     "call " helper "\n\t" \
+                     "1:\n" \
+                     ::"a" (rw) : "memory")
+
+#define __build_read_lock_const(rw, helper)   \
+        asm volatile(LOCK "subl $1,%0\n\t" \
+                     "jns 1f\n" \
+                     "pushl %%eax\n\t" \
+                     "leal %0,%%eax\n\t" \
+                     "call " helper "\n\t" \
+                     "popl %%eax\n\t" \
+                     "1:\n" \
+                     :"=m" (*(volatile int *)rw) : : "memory")
+
+#define __build_read_lock(rw, helper)   do { \
+                                                if (__builtin_constant_p(rw)) \
+                                                        __build_read_lock_const(rw, helper); \
+                                                else \
+                                                        __build_read_lock_ptr(rw, helper); \
+                                        } while (0)
+
+#define __build_write_lock_ptr(rw, helper) \
+        asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
+                     "jz 1f\n" \
+                     "call " helper "\n\t" \
+                     "1:\n" \
+                     ::"a" (rw) : "memory")
+
+#define __build_write_lock_const(rw, helper) \
+        asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
+                     "jz 1f\n" \
+                     "pushl %%eax\n\t" \
+                     "leal %0,%%eax\n\t" \
+                     "call " helper "\n\t" \
+                     "popl %%eax\n\t" \
+                     "1:\n" \
+                     :"=m" (*(volatile int *)rw) : : "memory")
+
+#define __build_write_lock(rw, helper)  do { \
+                                                if (__builtin_constant_p(rw)) \
+                                                        __build_write_lock_const(rw, helper); \
+                                                else \
+                                                        __build_write_lock_ptr(rw, helper); \
+                                        } while (0)
+
+#endif