#include <folly/detail/Futex.h>
#include <boost/intrusive/list.hpp>
+#include <folly/Indestructible.h>
#include <folly/ScopeGuard.h>
#include <folly/hash/Hash.h>
#include <folly/portability/SysSyscall.h>
#include <stdint.h>
#include <string.h>
+#include <array>
#include <cerrno>
#include <condition_variable>
#include <mutex>
std::mutex mutex_;
boost::intrusive::list<EmulatedFutexWaitNode> waiters_;
- static const size_t kNumBuckets = 4096;
+ static constexpr size_t const kNumBuckets = kIsMobile ? 256 : 4096;
static EmulatedFutexBucket& bucketFor(void* addr) {
- static auto gBuckets = new EmulatedFutexBucket[kNumBuckets];
- uint64_t mixedBits = folly::hash::twang_mix64(
- reinterpret_cast<uintptr_t>(addr));
- return gBuckets[mixedBits % kNumBuckets];
+ // Statically allocating this lets us use this in allocation-sensitive
+ // contexts. This relies on the assumption that std::mutex won't dynamically
+ // allocate memory, which we assume to be the case on Linux and iOS.
+ static Indestructible<std::array<EmulatedFutexBucket, kNumBuckets>>
+ gBuckets;
+ uint64_t mixedBits =
+ folly::hash::twang_mix64(reinterpret_cast<uintptr_t>(addr));
+ return (*gBuckets)[mixedBits % kNumBuckets];
}
};