51 lines
1.2 KiB
C++
51 lines
1.2 KiB
C++
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/*
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* one_time_construction.cpp
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*
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* Copyright 2006 The Android Open Source Project
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*
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* This file contains C++ ABI support functions for one time
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* constructors as defined in the "Run-time ABI for the ARM Architecture"
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* section 4.4.2
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*/
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#include <stddef.h>
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#include <sys/atomics.h>
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extern "C" int __futex_wait(volatile void *ftx, int val, const struct timespec *timeout);
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extern "C" int __futex_wake(volatile void *ftx, int count);
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extern "C" int __cxa_guard_acquire(int volatile * gv)
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{
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// 0 -> 2, return 1
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// 2 -> 6, wait and return 0
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// 6 untouched, wait and return 0
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// 1 untouched, return 0
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retry:
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if (__atomic_cmpxchg(0, 0x2, gv) == 0)
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return 1;
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__atomic_cmpxchg(0x2, 0x6, gv); // Indicate there is a waiter
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__futex_wait(gv, 0x6, NULL);
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if(*gv != 1) // __cxa_guard_abort was called, let every thread try since there is no return code for this condition
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goto retry;
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return 0;
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}
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extern "C" void __cxa_guard_release(int volatile * gv)
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{
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// 2 -> 1
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// 6 -> 1, and wake
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if (__atomic_cmpxchg(0x2, 0x1, gv) == 0)
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return;
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*gv = 0x1;
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__futex_wake(gv, 0x7fffffff);
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}
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extern "C" void __cxa_guard_abort(int volatile * gv)
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{
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*gv = 0;
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__futex_wake(gv, 0x7fffffff);
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}
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