1*0b57cec5SDimitry Andric //===-- mutex.h -------------------------------------------------*- C++ -*-===// 2*0b57cec5SDimitry Andric // 3*0b57cec5SDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4*0b57cec5SDimitry Andric // See https://llvm.org/LICENSE.txt for license information. 5*0b57cec5SDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6*0b57cec5SDimitry Andric // 7*0b57cec5SDimitry Andric //===----------------------------------------------------------------------===// 8*0b57cec5SDimitry Andric 9*0b57cec5SDimitry Andric #ifndef SCUDO_MUTEX_H_ 10*0b57cec5SDimitry Andric #define SCUDO_MUTEX_H_ 11*0b57cec5SDimitry Andric 12*0b57cec5SDimitry Andric #include "atomic_helpers.h" 13*0b57cec5SDimitry Andric #include "common.h" 14*0b57cec5SDimitry Andric 15*0b57cec5SDimitry Andric #include <string.h> 16*0b57cec5SDimitry Andric 17*0b57cec5SDimitry Andric #if SCUDO_FUCHSIA 18*0b57cec5SDimitry Andric #include <lib/sync/mutex.h> // for sync_mutex_t 19*0b57cec5SDimitry Andric #endif 20*0b57cec5SDimitry Andric 21*0b57cec5SDimitry Andric namespace scudo { 22*0b57cec5SDimitry Andric 23*0b57cec5SDimitry Andric class HybridMutex { 24*0b57cec5SDimitry Andric public: 25*0b57cec5SDimitry Andric void init() { memset(this, 0, sizeof(*this)); } 26*0b57cec5SDimitry Andric bool tryLock(); 27*0b57cec5SDimitry Andric NOINLINE void lock() { 28*0b57cec5SDimitry Andric if (tryLock()) 29*0b57cec5SDimitry Andric return; 30*0b57cec5SDimitry Andric // The compiler may try to fully unroll the loop, ending up in a 31*0b57cec5SDimitry Andric // NumberOfTries*NumberOfYields block of pauses mixed with tryLocks. This 32*0b57cec5SDimitry Andric // is large, ugly and unneeded, a compact loop is better for our purpose 33*0b57cec5SDimitry Andric // here. Use a pragma to tell the compiler not to unroll the loop. 34*0b57cec5SDimitry Andric #ifdef __clang__ 35*0b57cec5SDimitry Andric #pragma nounroll 36*0b57cec5SDimitry Andric #endif 37*0b57cec5SDimitry Andric for (u8 I = 0U; I < NumberOfTries; I++) { 38*0b57cec5SDimitry Andric yieldProcessor(NumberOfYields); 39*0b57cec5SDimitry Andric if (tryLock()) 40*0b57cec5SDimitry Andric return; 41*0b57cec5SDimitry Andric } 42*0b57cec5SDimitry Andric lockSlow(); 43*0b57cec5SDimitry Andric } 44*0b57cec5SDimitry Andric void unlock(); 45*0b57cec5SDimitry Andric 46*0b57cec5SDimitry Andric private: 47*0b57cec5SDimitry Andric static constexpr u8 NumberOfTries = 10U; 48*0b57cec5SDimitry Andric static constexpr u8 NumberOfYields = 10U; 49*0b57cec5SDimitry Andric 50*0b57cec5SDimitry Andric #if SCUDO_LINUX 51*0b57cec5SDimitry Andric atomic_u32 M; 52*0b57cec5SDimitry Andric #elif SCUDO_FUCHSIA 53*0b57cec5SDimitry Andric sync_mutex_t M; 54*0b57cec5SDimitry Andric #endif 55*0b57cec5SDimitry Andric 56*0b57cec5SDimitry Andric void lockSlow(); 57*0b57cec5SDimitry Andric }; 58*0b57cec5SDimitry Andric 59*0b57cec5SDimitry Andric class ScopedLock { 60*0b57cec5SDimitry Andric public: 61*0b57cec5SDimitry Andric explicit ScopedLock(HybridMutex &M) : Mutex(M) { Mutex.lock(); } 62*0b57cec5SDimitry Andric ~ScopedLock() { Mutex.unlock(); } 63*0b57cec5SDimitry Andric 64*0b57cec5SDimitry Andric private: 65*0b57cec5SDimitry Andric HybridMutex &Mutex; 66*0b57cec5SDimitry Andric 67*0b57cec5SDimitry Andric ScopedLock(const ScopedLock &) = delete; 68*0b57cec5SDimitry Andric void operator=(const ScopedLock &) = delete; 69*0b57cec5SDimitry Andric }; 70*0b57cec5SDimitry Andric 71*0b57cec5SDimitry Andric } // namespace scudo 72*0b57cec5SDimitry Andric 73*0b57cec5SDimitry Andric #endif // SCUDO_MUTEX_H_ 74