73 lines
1.7 KiB
C++
73 lines
1.7 KiB
C++
//===-- mutex.h -------------------------------------------------*- 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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#ifndef SCUDO_MUTEX_H_
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#define SCUDO_MUTEX_H_
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#include "atomic_helpers.h"
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#include "common.h"
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#include <string.h>
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#if SCUDO_FUCHSIA
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#include <lib/sync/mutex.h> // for sync_mutex_t
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#endif
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namespace scudo {
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class HybridMutex {
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public:
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bool tryLock();
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NOINLINE void lock() {
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if (LIKELY(tryLock()))
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return;
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// The compiler may try to fully unroll the loop, ending up in a
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// NumberOfTries*NumberOfYields block of pauses mixed with tryLocks. This
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// is large, ugly and unneeded, a compact loop is better for our purpose
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// here. Use a pragma to tell the compiler not to unroll the loop.
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#ifdef __clang__
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#pragma nounroll
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#endif
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for (u8 I = 0U; I < NumberOfTries; I++) {
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yieldProcessor(NumberOfYields);
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if (tryLock())
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return;
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}
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lockSlow();
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}
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void unlock();
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private:
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static constexpr u8 NumberOfTries = 8U;
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static constexpr u8 NumberOfYields = 8U;
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#if SCUDO_LINUX
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atomic_u32 M = {};
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#elif SCUDO_FUCHSIA
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sync_mutex_t M = {};
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#endif
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void lockSlow();
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};
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class ScopedLock {
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public:
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explicit ScopedLock(HybridMutex &M) : Mutex(M) { Mutex.lock(); }
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~ScopedLock() { Mutex.unlock(); }
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private:
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HybridMutex &Mutex;
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ScopedLock(const ScopedLock &) = delete;
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void operator=(const ScopedLock &) = delete;
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};
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} // namespace scudo
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#endif // SCUDO_MUTEX_H_
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