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From: John Birrell <jb@FreeBSD.org>
To: Perforce Change Reviews <perforce@freebsd.org>
Cc: 
Subject: PERFORCE change 135013 for review
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http://perforce.freebsd.org/chv.cgi?CH=135013

Change 135013 by jb@jb_freebsd1 on 2008/02/08 05:25:18

	Add a DTrace-specific lock function copied from atomic.h but
	named so that an fbt probe enabled function isn't called from
	the DTrace probe context (which would cause a double fault).

Affected files ...

.. //depot/projects/dtrace/src/sys/cddl/dev/dtrace/dtrace_debug.c#3 edit

Differences ...

==== //depot/projects/dtrace/src/sys/cddl/dev/dtrace/dtrace_debug.c#3 (text+ko) ====

@@ -52,6 +52,27 @@
 
 	return (res);
 }
+#elif defined(__i386__)
+static __inline int
+dtrace_cmpset_long(volatile u_long *dst, u_long exp, u_long src)
+{
+	u_char res;
+
+	__asm __volatile(
+	"       " lock "            	"
+	"       cmpxchgl %2,%1 ;        "
+	"       sete    %0 ;            "
+	"1:                             "
+	"# dtrace_cmpset_long"
+	: "=a" (res),                   /* 0 */
+	  "=m" (*dst)                   /* 1 */
+	: "r" (src),                    /* 2 */
+	  "a" (exp),                    /* 3 */
+	  "m" (*dst)                    /* 4 */
+	: "memory");
+
+	return (res);
+}
 #endif
 
 #define DTRACE_DEBUG_BUFR_SIZE	(32 * 1024)