forked from 0ad/0ad
janwas
f039e1ce76
prevent using mahaf if it's going to fail anyway module_init: add ModuleIsError (allows acpi and mahaf init routines to pass failure notification on to their second and later callers) counter: safer memory management This was SVN commit r5333.
75 lines
2.2 KiB
C++
75 lines
2.2 KiB
C++
/**
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* =========================================================================
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* File : module_init.cpp
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* Project : 0 A.D.
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* Description : helpers for module initialization/shutdown.
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* =========================================================================
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*/
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// license: GPL; see lib/license.txt
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#include "precompiled.h"
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#include "module_init.h"
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#include "lib/sysdep/cpu.h" // cpu_CAS, cpu_AtomicAdd
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// notes:
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// - value must be 0 to allow users to just define uninitialized static
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// variables (they don't have access to our MODULE_* symbols)
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// - unlike expected in-game operation, the self-tests require repeated
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// sequences of init/shutdown pairs. we therefore allow this in general
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// (resetting back to MODULE_UNINITIALIZED after shutdown) because
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// there's no real disadvantage other than loss of strictness.
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static const ModuleInitState MODULE_UNINITIALIZED = 0u;
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// (1..N = reference count)
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static const ModuleInitState MODULE_ERROR = ~1u;
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bool ModuleShouldInitialize(volatile ModuleInitState* pInitState)
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{
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// currently uninitialized, so give the green light.
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if(cpu_CAS(pInitState, MODULE_UNINITIALIZED, 1))
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return true;
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// increment reference count - unless already in a final state.
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retry:
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ModuleInitState latchedInitState = *pInitState;
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if(latchedInitState == MODULE_ERROR)
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return false;
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if(!cpu_CAS(pInitState, latchedInitState, latchedInitState+1))
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goto retry;
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return false;
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}
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bool ModuleShouldShutdown(volatile ModuleInitState* pInitState)
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{
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// decrement reference count - unless already in a final state.
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retry:
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ModuleInitState latchedInitState = *pInitState;
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if(latchedInitState == MODULE_UNINITIALIZED || latchedInitState == MODULE_ERROR)
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return false;
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if(!cpu_CAS(pInitState, latchedInitState, latchedInitState-1))
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goto retry;
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// refcount reached zero => allow shutdown.
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if(latchedInitState-1 == MODULE_UNINITIALIZED)
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return true;
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return false;
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}
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void ModuleSetError(volatile ModuleInitState* pInitState)
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{
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*pInitState = MODULE_ERROR;
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}
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bool ModuleIsError(volatile ModuleInitState* pInitState)
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{
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return (*pInitState == MODULE_ERROR);
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}
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