diff options
| -rw-r--r-- | compiler-rt/lib/builtins/cpu_model.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/compiler-rt/lib/builtins/cpu_model.c b/compiler-rt/lib/builtins/cpu_model.c index 5f51828..001467a9 100644 --- a/compiler-rt/lib/builtins/cpu_model.c +++ b/compiler-rt/lib/builtins/cpu_model.c @@ -1285,6 +1285,14 @@ static bool isKnownAndSupported(const char *name) { } void __init_cpu_features_resolver(void) { + // On Darwin platforms, this may be called concurrently by multiple threads + // because the resolvers that use it are called lazily at runtime (unlike on + // ELF platforms, where IFuncs are resolved serially at load time). This + // function's effect on __aarch64_cpu_features should be idempotent, but even + // so we need dispatch_once to resolve the race condition. Dispatch is + // available through libSystem, which we need anyway for the sysctl, so this + // does not add a new dependency. + static dispatch_once_t onceToken = 0; dispatch_once(&onceToken, ^{ // https://developer.apple.com/documentation/kernel/1387446-sysctlbyname/determining_instruction_set_characteristics |