| // Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| #include "vm/bss_relocs.h" |
| #include "vm/native_symbol.h" |
| #include "vm/runtime_entry.h" |
| #include "vm/thread.h" |
| |
| namespace dart { |
| |
| void BSS::InitializeBSSEntry(BSS::Relocation relocation, |
| uword new_value, |
| uword* bss_start) { |
| std::atomic<uword>* slot = reinterpret_cast<std::atomic<uword>*>( |
| &bss_start[BSS::RelocationIndex(relocation)]); |
| uword old_value = slot->load(std::memory_order_relaxed); |
| // FullSnapshotReader::ReadProgramSnapshot, and thus BSS::Initialize, can |
| // get called multiple times for the same isolate in different threads, though |
| // the initialized value will be consistent and thus change only once. Avoid |
| // calling compare_exchange_strong unless we actually need to change the |
| // value, to avoid spurious read/write races by TSAN. |
| if (old_value == new_value) return; |
| if (!slot->compare_exchange_strong(old_value, new_value, |
| std::memory_order_relaxed)) { |
| RELEASE_ASSERT(old_value == new_value); |
| } |
| } |
| |
| void BSS::Initialize(Thread* current, uword* bss_start, bool vm) { |
| // TODO(https://dartbug.com/52579): Remove. |
| InitializeBSSEntry(Relocation::DRT_GetFfiCallbackMetadata, |
| reinterpret_cast<uword>(DLRT_GetFfiCallbackMetadata), |
| bss_start); |
| InitializeBSSEntry(Relocation::DRT_ExitTemporaryIsolate, |
| reinterpret_cast<uword>(DLRT_ExitTemporaryIsolate), |
| bss_start); |
| } |
| |
| } // namespace dart |
