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61 lines
1.9 KiB
C++
61 lines
1.9 KiB
C++
/*! \file
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* \brief Contains the class Spinlock
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*/
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#pragma once
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#include "../types.h"
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/*! \brief Using Spinlocks, it is possible to serialize blocks of code
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* that might otherwise run in parallel on multiple CPU cores,
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* or be interleaved due to interrupts or scheduling.
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*
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* \ingroup sync
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*
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* Synchronization is implemented using a lock variable. Once a thread enters
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* the critical area, it sets the lock variable (to a non-zero value); when
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* this thread leaves the critical area, it resets the lock variable to zero.
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* Threads trying to enter an already locked critical area, actively wait,
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* continuously checking until the critical area is free again.
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*
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* Use the following two GCC intrinsics
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* - `bool __atomic_test_and_set(void *ptr, int memorder)`
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* - `void __atomic_clear (bool *ptr, int memorder)`
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*
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* These intrinsics are translated into atomic, architecture-specific
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* CPU instructions.
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*
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* If you want that things just work, choose __ATOMIC_SEQ_CST as memorder.
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* This is not the most efficient memory order but works reasonably well.
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*
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* <a
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* href="https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html">Atomic
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* Builtins in GCC manual</a>
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*/
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class Spinlock {
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// Prevent copies and assignments
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Spinlock(const Spinlock& copy) = delete;
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Spinlock& operator=(const Spinlock&) = delete;
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public:
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/*! \brief Constructor; Initializes as unlocked.
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*
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* \todo(12) Complete Constructor (for \MPStuBS, or use \ref Ticketlock)
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*
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*/
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consteval Spinlock() {}
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/*! \brief Enters the critical area. In case the area is already locked,
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* \ref lock() will actively wait until the area can be entered.
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*
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* \see \ref Core::pause()
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* \todo(12) Implement Method (for \MPStuBS, or use \ref Ticketlock)
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*/
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void lock() {}
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/*! \brief Unblocks the critical area.
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*
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* \todo(12) Implement Method (for \MPStuBS, or use \ref Ticketlock)
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*/
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void unlock() {}
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};
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