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try again to fix trouble mfence use for futures

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This commit is contained in:
Matthew Flatt 2010-09-16 06:27:55 -06:00
parent 11f6ec1b98
commit d4b0048d42
2 changed files with 18 additions and 10 deletions
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2
src/racket/sconfig.h
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@ -1347,7 +1347,7 @@
/* MZ_USE_JIT_I386 enables the JIT for x86 */
/* MZ_USE_JIT_X86_65 enables the JIT for x86_64 */
/* MZ_USE_JIT_X86_64 enables the JIT for x86_64 */
/* MZ_USE_JIT_PPC enables the JIT for PowerPC */

26
src/racket/src/future.c
View File

@ -526,15 +526,23 @@ void scheme_future_block_until_gc()
}
if (cpucount > 1) {
/* `cpucount' is not actually a complete test for whether mfence
should work, but the probability of someone using futures
on a multiprocessor system without SSE2 seems very low. */
#ifdef _MSC_VER
__asm {
mfence
}
#else
asm("mfence");
/* In principle, we need some sort of fence to ensure that future
threads see the change to the fuel pointer. The MFENCE
instruction would do that, but it requires SSE2. The CPUID
instruction is a non-privileged serializing instruction that
should be available on any x86 platform that runs threads. */
#if defined(i386) || defined(__i386__) || defined(__x86_64) || defined(__x86_64__) || defined(__amd64__)
# ifdef _MSC_VER
{
int r[4];
__cpuid(r, 0);
}
# else
{
int _eax, _ebx, _ecx, _edx, op = 0;
asm ("cpuid" : "=a" (_eax), "=b" (_ebx), "=c" (_ecx), "=d" (_edx) : "a" (op));
}
# endif
#endif
}