99 lines
1.9 KiB
C++
99 lines
1.9 KiB
C++
/*
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* \brief Basic locking primitive
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* \author Norman Feske
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* \date 2006-07-26
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*/
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/*
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* Copyright (C) 2006-2017 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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#ifndef _INCLUDE__BASE__CANCELABLE_LOCK_H_
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#define _INCLUDE__BASE__CANCELABLE_LOCK_H_
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#include <base/lock_guard.h>
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#include <base/blocking.h>
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namespace Genode {
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class Thread;
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class Cancelable_lock;
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}
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class Genode::Cancelable_lock
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{
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private:
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class Applicant
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{
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private:
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Thread *_thread_base;
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Applicant *_to_wake_up;
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public:
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explicit Applicant(Thread *thread_base)
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: _thread_base(thread_base), _to_wake_up(0) { }
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void applicant_to_wake_up(Applicant *to_wake_up) {
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_to_wake_up = to_wake_up; }
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Applicant *applicant_to_wake_up() { return _to_wake_up; }
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Thread *thread_base() { return _thread_base; }
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/**
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* Called from previous lock owner
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*/
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void wake_up();
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bool operator == (Applicant &a) { return _thread_base == a.thread_base(); }
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bool operator != (Applicant &a) { return _thread_base != a.thread_base(); }
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};
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/*
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* Note that modifications of the applicants queue must be performed
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* atomically. Hence, we use the additional spinlock here.
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*/
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volatile int _spinlock_state = 0;
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volatile int _state = 0;
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Applicant * volatile _last_applicant = nullptr;
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Applicant _owner;
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public:
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enum State { LOCKED, UNLOCKED };
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/**
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* Constructor
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*/
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explicit Cancelable_lock(State initial = UNLOCKED);
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/**
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* Try to aquire the lock and block while the lock is not free
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*
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* \throw Genode::Blocking_canceled
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*/
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void lock();
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/**
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* Release lock
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*/
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void unlock();
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/**
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* Lock guard
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*/
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typedef Genode::Lock_guard<Cancelable_lock> Guard;
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};
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#endif /* _INCLUDE__BASE__CANCELABLE_LOCK_H_ */
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