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