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多个线程同时读取静态变量

[英]Multiple threads reading static variable at the same time

原文 2011-12-07 12:48:29 6 3 c#/ .net/ multithreading/ static/ static-variables

My question may be newbie or duplicate, but i wonder what is happening when several threads try to read a static variable at the same time. 我的问题可能是新手或重复，但我想知道当几个线程同时尝试读取静态变量时会发生什么。 I'm not interesting in synchronization now, i just want to know are they reading it instantly or by turn? 我现在对同步并不感兴趣，我只是想知道他们是立即还是轮流阅读？

UPDATE: my question is more in domain of physics or smth like that(= if it is the same moment of time when threads read the variable. 更新：我的问题更多的是物理领域或类似的那样（=如果它是线程读取变量的同一时刻。

3 个解决方案

If a value of variable does not change (any thread does not write a value) so read by multiple threads would be a safe operation and does not require an additional synchronization like locking. 如果变量的值没有改变（任何线程没有写入值），那么多线程读取将是一个安全的操作，并且不需要像锁定那样的额外同步。 Otherwise you have to consider locking for write access operations. 否则，您必须考虑锁定写访问操作。

UPDATE: Regarding question update 更新：关于问题更新

Physically in scope of a single core CPU only one instruction (simplified, ignore CPU pipelines) could be executed so no chance to access the same memory location in a same quant of a time. 物理上在单核CPU的范围内，只能执行一条指令（简化，忽略CPU流水线），因此没有机会在相同的时间内访问相同的存储单元。

他们无法真正同时访问它 - 在某些时候CPU会对读取进行排序。

If it is a static type that is read in one go a processor core (on all platforms) then it is an atomic operation. 如果它是一个读取的静态类型去处理器核心（在所有平台上）那么它是一个原子操作。 If it is a larger type that takes more than one operation to read or write then it is not atomic and you could read dodgy values that are a product of another thread changing it partially while you are reading/writing it. 如果它是一个较大的类型，需要多个操作来读取或写入，那么它不是原子的，您可以读取在您读取/写入时部分更改它的另一个线程的产品的狡猾值。