2 files changed, 55 insertions, 0 deletions

diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index f871e04b6965..e10cf070ede0 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -30,6 +30,7 @@ ifeq ($(CONFIG_X86_32),y)
         lib-y += checksum_32.o
         lib-y += strstr_32.o
         lib-y += semaphore_32.o string_32.o
+        lib-y += cmpxchg.o
 ifneq ($(CONFIG_X86_CMPXCHG64),y)
         lib-y += cmpxchg8b_emu.o atomic64_386_32.o
 endif
diff --git a/arch/x86/lib/cmpxchg.c b/arch/x86/lib/cmpxchg.c
new file mode 100644
index 000000000000..5d619f6df3ee
--- /dev/null
+++ b/arch/x86/lib/cmpxchg.c
@@ -0,0 +1,54 @@
+/*
+ * cmpxchg*() fallbacks for CPU not supporting these instructions
+ */
+
+#include <linux/kernel.h>
+#include <linux/smp.h>
+#include <linux/module.h>
+
+#ifndef CONFIG_X86_CMPXCHG
+unsigned long cmpxchg_386_u8(volatile void *ptr, u8 old, u8 new)
+{
+        u8 prev;
+        unsigned long flags;
+
+        /* Poor man's cmpxchg for 386. Unsuitable for SMP */
+        local_irq_save(flags);
+        prev = *(u8 *)ptr;
+        if (prev == old)
+                *(u8 *)ptr = new;
+        local_irq_restore(flags);
+        return prev;
+}
+EXPORT_SYMBOL(cmpxchg_386_u8);
+
+unsigned long cmpxchg_386_u16(volatile void *ptr, u16 old, u16 new)
+{
+        u16 prev;
+        unsigned long flags;
+
+        /* Poor man's cmpxchg for 386. Unsuitable for SMP */
+        local_irq_save(flags);
+        prev = *(u16 *)ptr;
+        if (prev == old)
+                *(u16 *)ptr = new;
+        local_irq_restore(flags);
+        return prev;
+}
+EXPORT_SYMBOL(cmpxchg_386_u16);
+
+unsigned long cmpxchg_386_u32(volatile void *ptr, u32 old, u32 new)
+{
+        u32 prev;
+        unsigned long flags;
+
+        /* Poor man's cmpxchg for 386. Unsuitable for SMP */
+        local_irq_save(flags);
+        prev = *(u32 *)ptr;
+        if (prev == old)
+                *(u32 *)ptr = new;
+        local_irq_restore(flags);
+        return prev;
+}
+EXPORT_SYMBOL(cmpxchg_386_u32);
+#endif