【发布时间】：2012-09-23 19:26:05
【问题描述】：
我偶然发现了 Queued Spinlock，并想用 C++ 实现。我在谷歌上搜索了一些信息，但无法获得适当的文档。
任何文档/实施提示将不胜感激。
提前致谢
我对 Michael Brown 指出的代码有以下疑问
// represents processor in wait queue of the spinlock
struct qsl_entry
{
// next processor in the queue that is waiting to enter section
qsl_entry* next;
// indicates whether the access to section has been granted to processor
int state;
};
// queued spinlock
struct qsl
{
// the first processor in the queue that is waiting to enter section
qsl_entry* head;
};
// requests access to critical section guarded by the spinlock,
// if the section is already taken it puts processor to wait
// and insert it into queue
// lck - queued lock that used to guard section
// ent - entry that represent processor in queue of the spinlock
void lock_qsl(qsl* lck, qsl_entry* ent)
{
__asm
{
mov eax, ent;
mov ebx, lck;
// prepare queue entry
mov [eax], 0;
mov edx, eax;
mov [eax]qsl_entry.state, 1;
// store it as the last entry of the queue -- Is this what is line is doing ?
// ebx contains address of lck & [ ebx ] refers to address pointed by lck &
// it is over written to ent. eax now contains the memory the lck was pointing to.
lock xchg [ebx],eax;
// if the section available grant access to processor?
test eax, eax;
jz enter_section;
// link new entry with the rest of queue -- really ? are we nt overwritting
// the next pointer here ?
mov [eax],edx
// wait for processor's turn
wait1:
pause;
cmp [edx]qsl_entry.state, 1;
je wait1;
enter_section:
}
}
这个实现是否正确？我怀疑！
【问题讨论】：
-
codeproject.com/Tips/100195/Queued-spinlocks 似乎是一个合适的实现
-
啊，是的，对不起，您的问题确实说明了您想要的详细信息。你追求什么细节？排队的自旋锁是自旋锁的链表，每个进入临界区的线程都有一个。文章指出，当在多个处理器上仅使用一个自旋锁时，这有助于解决内存和缓存问题
-
从概念上讲，这类似于信号量。除了计数器被拆分为布尔值，并放置在链表（fifo）中。如果您想要更多可能有帮助的理论。否则，上面链接的实现是你最好的选择
-
嘿嘿。我觉得这方面的细节最好放在维基百科上。因此，将尝试输入并返回此处。 p.s.代码是正确的。
-
只要数据在双字边界上对齐（编译器会这样做），那么
cmp操作就是原子的。
标签： c++ synchronization linux-kernel mutex spinlock