locks.md 2.2 KB
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Types of Locks and Their Rules
Introduction
The DragonOS kernel implements several types of locks, which can be broadly categorized into two types:
- Sleepable locks
- Spin locks
Types of Locks
Sleepable Locks
Sleepable locks can only be acquired in a context that is preemptible.
In DragonOS, the following sleepable locks are implemented:
- semaphore
- mutex_t
Spin Locks
- spinlock_t
- {ref}
RawSpinLock <_spinlock_doc_rawspinlock>(Rust version of spinlock_t, but incompatible with spinlock_t) - {ref}
SpinLock <_spinlock_doc_spinlock>—— Built on top of RawSpinLock, it wraps a guard, binding the lock and the data it protects into a single structure. This allows for compile-time checks to prevent accessing data without holding the lock.
When a process acquires a spin lock, it changes the lock count in the PCB, thereby implicitly disabling preemption. To provide more flexible operations, spinlock also provides the following methods:
| Suffix | Description |
|---|---|
| _irq() | Disable interrupts when acquiring the lock, enable them when releasing |
| _irqsave()/_irqrestore() | Save the interrupt state when acquiring the lock, and restore it when releasing |
Detailed Introduction
Detailed Introduction to Spin Locks
For a detailed introduction to spin locks, please refer to the document: {ref}自旋锁 <_spinlock_doc>
Semaphore
A semaphore is implemented based on a counter.
When the available resources are insufficient, a process attempting to perform a down operation on the semaphore will be put to sleep until the resources become available.
Mutex
Please refer to {ref}Mutex文档 <_mutex_doc>