[PATCH] Fix libstdc++/11784 - atomic __exchange_and_add() brokenfor ColdFire targets

[Bernardo Innocenti <bernie at develer dot com>]

NOTE: this new patch contains additional fixes for __mcf5400__ and __mcpu32__.
Please ignore the old patch.


This patch replaces all m68k specific variants of __exchange_and_add() with
a single version using either TAS (for 680x0, CPU32 and 5407) or BTST, which
behaves atomically on non-SMP systems.

Previously, ColdFire targets used the variant for vxWorks/__embedded__.
This code path was disabling interrupts to update the counter atomically,
but user apps linking with libstdc++ would segfault because "move #0,%sr"
is a privileged opcode.

There was also a generic, thread-unsafe C version to be used as a last
resort. now it's gone since all m68k targets do have the BSET instruction.


2003-08-06  Bernardo Innocenti  <bernie@develer.com>

	PR libstdc++/11784
	* libstdc++-v3/config/cpu/m68k/atomicity.h (__exchange_and_add): Replace variants with new BSET-based version.


--- gcc-3.4.orig/libstdc++-v3/config/cpu/m68k/atomicity.h.orig	2003-07-24 18:58:58.000000000 +0200
+++ gcc-3.4/libstdc++-v3/config/cpu/m68k/atomicity.h	2003-07-24 23:23:35.000000000 +0200
@@ -32,8 +32,9 @@

typedef int _Atomic_word;

-#if defined(__mc68020__) || defined(__mc68030__) \
-    || defined(__mc68040__) || defined(__mc68060__)
+#if ( defined(__mc68020__) || defined(__mc68030__) \
+      || defined(__mc68040__) || defined(__mc68060__) ) \
+    && !defined(__mcpu32__)
// These variants support compare-and-swap.

static inline _Atomic_word 
@@ -74,8 +75,7 @@
  return __result;
}

-#elif !defined(__mcf5200__) && !defined(__mcf5300__)
-// 68000, 68010, cpu32 and 5400 support test-and-set.
+#else

template <int __inst>
struct __Atomicity_lock
@@ -94,10 +94,28 @@
{
  _Atomic_word __result;

+// bset with no immediate addressing
+#if defined(__mcf5200__) || defined(__mcf5300__) || defined(__mcf5400__)
+  __asm__ __volatile__("1: bset.b #7,%0@\n\tjbne 1b"
+		      : /* no outputs */
+		      : "a"(&__Atomicity_lock<0>::_S_atomicity_lock)
+		      : "cc", "memory");
+
+// bset with immediate addressing
+#elif defined(__mc68000__)
+  __asm__ __volatile__("1: bset.b #7,%0\n\tjbne 1b"
+		      : "=m"(__Atomicity_lock<0>::_S_atomicity_lock)
+		      : "m"(__Atomicity_lock<0>::_S_atomicity_lock)
+		      : "cc");
+
+#else // 680x0, cpu32, 5400 support test-and-set.
  __asm__ __volatile__("1: tas %0\n\tjbne 1b"
		       : "=m"(__Atomicity_lock<0>::_S_atomicity_lock)
-		       : "m"(__Atomicity_lock<0>::_S_atomicity_lock));
+		       : "m"(__Atomicity_lock<0>::_S_atomicity_lock)
+		       : "cc");

+#endif
+  
  __result = *__mem;
  *__mem = __result + __val;

@@ -106,45 +124,7 @@
  return __result;
}

-#elif defined(__vxWorks__) || defined(__embedded__)
-// The best we can hope for is to disable interrupts, which we
-// can only do from supervisor mode.
-
-static inline _Atomic_word 
-__attribute__ ((__unused__))
-__exchange_and_add (volatile _Atomic_word *__mem, int __val)
-{
-  _Atomic_word __result;
-  short __level, __tmpsr;
-  __asm__ __volatile__ ("move%.w %%sr,%0\n\tor%.l %0,%1\n\tmove%.w %1,%%sr"
-		  	: "=d"(__level), "=d"(__tmpsr) : "1"(0x700));
-
-  __result = *__mem;
-  *__mem = __result + __val;
-
-  __asm__ __volatile__ ("move%.w %0,%%sr" : : "d"(__level));
-
-  return __result;
-}
-
-#else
-// These variants do not support any atomic operations at all.
-
-#warning "__exchange_and_add is not atomic for this target"
-
-static inline _Atomic_word
-__attribute__ ((__unused__))
-__exchange_and_add (volatile _Atomic_word *__mem, int __val)
-{
-  _Atomic_word __result;
-
-  __result = *__mem;
-  *__mem = __result + __val;
-
-  return __result;
-}
-
-#endif /* CAS / IRQ / TAS */
+#endif /* TAS / BSET */

static inline void
__attribute__ ((__unused__))
@@ -155,4 +135,4 @@
  (void) __exchange_and_add (__mem, __val);
}

-#endif /* atomicity.h */
+#endif /* !_GLIBCXX_ATOMICITY_H */


--
 // Bernardo Innocenti - Develer S.r.l., R&D dept.
\X/  http://www.develer.com/

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