RFR: 8185723: Zero: segfaults on Power PC 32-bit

[John Paul Adrian Glaubitz]

On 08/03/2017 12:06 PM, Andrew Haley wrote:
> On 03/08/17 10:32, John Paul Adrian Glaubitz wrote:
>> I think either __arch_compare_and_exchange_val_64_acq() or
>> atomic_exchange_acq() from [1] should help.
> 
> The first one is what you want, assuming that you're happy to
> write to an operand you're supposed to only read.

I'm trying this now:

--- jdk9-fe8466adaef8.orig/hotspot/src/os_cpu/linux_zero/vm/os_linux_zero.hpp   2017-07-14 06:32:55.000000000 +0200
+++ jdk9-fe8466adaef8/hotspot/src/os_cpu/linux_zero/vm/os_linux_zero.hpp        2017-08-03 13:59:40.257640677 +0200
@@ -48,6 +48,22 @@
                   "std %0, 0(%2)\n"
                   : "=r"(tmp)
                   : "a"(src), "a"(dst));
+#elif defined(M68K)
+# define __arch_compare_and_exchange_val_64_acq(mem, newval, oldval)   \
+    ({ __typeof (*(mem)) __ret;                                                \
+      __typeof (mem) __memp = (mem);                                   \
+      __asm __volatile ("cas2%.l %0:%R0,%1:%R1,(%2):(%3)"              \
+                       : "=d" (__ret)                                  \
+                       : "d" ((__typeof (*(mem))) (newval)), "r" (__memp), \
+                       "r" ((char *) __memp + 4), "0" (oldval)         \
+                       : "memory");                                    \
+      __ret; })
+
+    jlong tmp;
+    do {
+      tmp = *(jlong *)src;
+    } while(!__arch_compare_and_exchange_val_64_acq(src, tmp, tmp));
+    while(__arch_compare_and_exchange_val_64_acq(dst, *(jlong*)dst, tmp));
 #else
     *(jlong *) dst = *(jlong *) src;
 #endif

I have no idea whether it's correct, but I'll find out.

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz at debian.org
`. `'   Freie Universitaet Berlin - glaubitz at physik.fu-berlin.de
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