2946cd7010
to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
110 lines
3.4 KiB
C++
110 lines
3.4 KiB
C++
//===-- scudo_tsd_shared.cpp ------------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// Scudo shared TSD implementation.
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///
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//===----------------------------------------------------------------------===//
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#include "scudo_tsd.h"
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#if !SCUDO_TSD_EXCLUSIVE
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namespace __scudo {
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static pthread_once_t GlobalInitialized = PTHREAD_ONCE_INIT;
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pthread_key_t PThreadKey;
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static atomic_uint32_t CurrentIndex;
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static ScudoTSD *TSDs;
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static u32 NumberOfTSDs;
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static u32 CoPrimes[SCUDO_SHARED_TSD_POOL_SIZE];
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static u32 NumberOfCoPrimes = 0;
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#if SANITIZER_LINUX && !SANITIZER_ANDROID
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__attribute__((tls_model("initial-exec")))
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THREADLOCAL ScudoTSD *CurrentTSD;
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#endif
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static void initOnce() {
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CHECK_EQ(pthread_key_create(&PThreadKey, NULL), 0);
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initScudo();
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NumberOfTSDs = Min(Max(1U, GetNumberOfCPUsCached()),
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static_cast<u32>(SCUDO_SHARED_TSD_POOL_SIZE));
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TSDs = reinterpret_cast<ScudoTSD *>(
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MmapOrDie(sizeof(ScudoTSD) * NumberOfTSDs, "ScudoTSDs"));
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for (u32 I = 0; I < NumberOfTSDs; I++) {
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TSDs[I].init();
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u32 A = I + 1;
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u32 B = NumberOfTSDs;
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while (B != 0) { const u32 T = A; A = B; B = T % B; }
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if (A == 1)
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CoPrimes[NumberOfCoPrimes++] = I + 1;
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}
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}
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ALWAYS_INLINE void setCurrentTSD(ScudoTSD *TSD) {
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#if SANITIZER_ANDROID
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*get_android_tls_ptr() = reinterpret_cast<uptr>(TSD);
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#elif SANITIZER_LINUX
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CurrentTSD = TSD;
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#else
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CHECK_EQ(pthread_setspecific(PThreadKey, reinterpret_cast<void *>(TSD)), 0);
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#endif // SANITIZER_ANDROID
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}
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void initThread(bool MinimalInit) {
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pthread_once(&GlobalInitialized, initOnce);
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// Initial context assignment is done in a plain round-robin fashion.
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u32 Index = atomic_fetch_add(&CurrentIndex, 1, memory_order_relaxed);
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setCurrentTSD(&TSDs[Index % NumberOfTSDs]);
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}
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ScudoTSD *getTSDAndLockSlow(ScudoTSD *TSD) {
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if (NumberOfTSDs > 1) {
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// Use the Precedence of the current TSD as our random seed. Since we are in
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// the slow path, it means that tryLock failed, and as a result it's very
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// likely that said Precedence is non-zero.
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u32 RandState = static_cast<u32>(TSD->getPrecedence());
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const u32 R = Rand(&RandState);
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const u32 Inc = CoPrimes[R % NumberOfCoPrimes];
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u32 Index = R % NumberOfTSDs;
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uptr LowestPrecedence = UINTPTR_MAX;
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ScudoTSD *CandidateTSD = nullptr;
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// Go randomly through at most 4 contexts and find a candidate.
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for (u32 I = 0; I < Min(4U, NumberOfTSDs); I++) {
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if (TSDs[Index].tryLock()) {
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setCurrentTSD(&TSDs[Index]);
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return &TSDs[Index];
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}
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const uptr Precedence = TSDs[Index].getPrecedence();
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// A 0 precedence here means another thread just locked this TSD.
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if (UNLIKELY(Precedence == 0))
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continue;
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if (Precedence < LowestPrecedence) {
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CandidateTSD = &TSDs[Index];
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LowestPrecedence = Precedence;
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}
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Index += Inc;
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if (Index >= NumberOfTSDs)
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Index -= NumberOfTSDs;
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}
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if (CandidateTSD) {
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CandidateTSD->lock();
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setCurrentTSD(CandidateTSD);
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return CandidateTSD;
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}
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}
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// Last resort, stick with the current one.
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TSD->lock();
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return TSD;
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}
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} // namespace __scudo
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#endif // !SCUDO_TSD_EXCLUSIVE
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