test-and-set

does the atomic instruction involve the kernel

由 我是研究僧i 提交于 2021-02-11 07:05:54
问题 I'm reading this link to learn about futex of Linux. Here is something that I don't understand. In order to acquire the lock, an atomic test-and-set instruction (such as cmpxchg()) can be used to test for 0 and set to 1. In this case, the locking thread acquires the lock without involving the kernel (and the kernel has no knowledge that this futex exists). When the next thread attempts to acquire the lock, the test for zero will fail and the kernel needs to be involved. I don't quite

does the atomic instruction involve the kernel

由 六眼飞鱼酱① 提交于 2021-02-11 07:05:49
问题 I'm reading this link to learn about futex of Linux. Here is something that I don't understand. In order to acquire the lock, an atomic test-and-set instruction (such as cmpxchg()) can be used to test for 0 and set to 1. In this case, the locking thread acquires the lock without involving the kernel (and the kernel has no knowledge that this futex exists). When the next thread attempts to acquire the lock, the test for zero will fail and the kernel needs to be involved. I don't quite

does the atomic instruction involve the kernel

由 三世轮回 提交于 2021-02-11 07:04:45
问题 I'm reading this link to learn about futex of Linux. Here is something that I don't understand. In order to acquire the lock, an atomic test-and-set instruction (such as cmpxchg()) can be used to test for 0 and set to 1. In this case, the locking thread acquires the lock without involving the kernel (and the kernel has no knowledge that this futex exists). When the next thread attempts to acquire the lock, the test for zero will fail and the kernel needs to be involved. I don't quite

What is Test-and-Set used for?

由 。_饼干妹妹 提交于 2019-12-20 09:53:07
问题 After reading the Test-and-Set Wikipedia entry, I am still left with the question "What would a Test-and-Set be used for?" I realize that you can use it to implement Mutex (as described in wikipedia), but what other uses does it have? 回答1: You use it any time you want to write data to memory after doing some work and make sure another thread hasn't overwritten the destination since you started. A lot of lock/mutex-free algorithms take this form. 回答2: A good example is "increment." Say two

What is Test-and-Set used for?

由 耗尽温柔 提交于 2019-12-20 09:51:17
问题 After reading the Test-and-Set Wikipedia entry, I am still left with the question "What would a Test-and-Set be used for?" I realize that you can use it to implement Mutex (as described in wikipedia), but what other uses does it have? 回答1: You use it any time you want to write data to memory after doing some work and make sure another thread hasn't overwritten the destination since you started. A lot of lock/mutex-free algorithms take this form. 回答2: A good example is "increment." Say two

What is Test-and-Set used for?

由 好久不见. 提交于 2019-12-02 19:36:11
After reading the Test-and-Set Wikipedia entry , I am still left with the question "What would a Test-and-Set be used for?" I realize that you can use it to implement Mutex (as described in wikipedia), but what other uses does it have? moonshadow You use it any time you want to write data to memory after doing some work and make sure another thread hasn't overwritten the destination since you started. A lot of lock/mutex-free algorithms take this form. A good example is "increment." Say two threads execute a = a + 1 . Say a starts with the value 100 . If both threads are running at the same

Atomic Instruction

由 天大地大妈咪最大 提交于 2019-11-30 09:02:17
问题 What do you mean by Atomic instructions? How does the following become Atomic? TestAndSet int TestAndSet(int *x){ register int temp = *x; *x = 1; return temp; } From a software perspective, if one does not want to use non-blocking synchronization primitives, how can one ensure Atomicity of instruction? is it possible only at Hardware or some assembly level directive optimization can be used? 回答1: Some machine instructions are intrinsically atomic - for example, reading and writing properly

Atomic Instruction

由 白昼怎懂夜的黑 提交于 2019-11-29 11:07:50
What do you mean by Atomic instructions? How does the following become Atomic? TestAndSet int TestAndSet(int *x){ register int temp = *x; *x = 1; return temp; } From a software perspective, if one does not want to use non-blocking synchronization primitives, how can one ensure Atomicity of instruction? is it possible only at Hardware or some assembly level directive optimization can be used? Some machine instructions are intrinsically atomic - for example, reading and writing properly aligned values of the native processor word size is atomic on many architectures . This means that hardware
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