The inline assembly used for the x86/x86-64 host testandset routine is bogus.
The operand constraints are wrong (Fails to compile at -O0).
Also the return value is incorrect. It should return 0 if the lock was
successfully acquired.
Patch below fixes it. The additional sete test is unnecessary, we can just use
the comparison/writeback value.
Paul
Index: exec-all.h
===================================================================
RCS file: /cvsroot/qemu/qemu/exec-all.h,v
retrieving revision 1.26
diff -u -p -r1.26 exec-all.h
--- exec-all.h 10 Jan 2005 23:23:48 -0000 1.26
+++ exec-all.h 6 Feb 2005 14:35:43 -0000
@@ -392,28 +392,24 @@ static inline int testandset (int *p)
#ifdef __i386__
static inline int testandset (int *p)
{
- char ret;
- long int readval;
-
- __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
- : "=q" (ret), "=m" (*p), "=a" (readval)
- : "r" (1), "m" (*p), "a" (0)
- : "memory");
- return ret;
+ long int readval = 0;
+
+ __asm__ __volatile__ ("lock; cmpxchgl %2, %0"
+ : "+m" (*p), "+a" (readval)
+ : "r" (1));
+ return readval;
}
#endif
#ifdef __x86_64__
static inline int testandset (int *p)
{
- char ret;
- int readval;
-
- __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
- : "=q" (ret), "=m" (*p), "=a" (readval)
- : "r" (1), "m" (*p), "a" (0)
- : "memory");
- return ret;
+ long int readval = 0;
+
+ __asm__ __volatile__ ("lock; cmpxchgl %2, %0"
+ : "+m" (*p), "+a" (readval)
+ : "r" (1));
+ return readval;
}
#endif
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