From: Thomas Gleixner <tglx@linutronix.de>
Date: Sat, 16 Feb 2008 13:05:01 +0000 (+0100)
Subject: x86: no robust/pi futex for real i386 CPUs
X-Git-Tag: v2.6.25-rc4~159^2
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=f18edc95a37a901ffcbe91f5e05105f916a04fae;p=linux-2.6-omap-h63xx.git

x86: no robust/pi futex for real i386 CPUs

Real i386 CPUs do not have cmpxchg instructions. Catch it before
crashing on an invalid opcode.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---

diff --git a/include/asm-x86/futex.h b/include/asm-x86/futex.h
index cd9f894dd2d..c9952ea9f69 100644
--- a/include/asm-x86/futex.h
+++ b/include/asm-x86/futex.h
@@ -102,6 +102,13 @@ futex_atomic_op_inuser(int encoded_op, int __user *uaddr)
 static inline int
 futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 {
+
+#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_BSWAP)
+	/* Real i386 machines have no cmpxchg instruction */
+	if (boot_cpu_data.x86 == 3)
+		return -ENOSYS;
+#endif
+
 	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
 		return -EFAULT;