question on memory fence

question on memory fence

softarts's picture

take Compare and Swap as en example:

free(coid * newhead)

do

{

oldhead = next;

newhead->next = next;

//asm volatile("mfence":::"memory");

}while(!CAS(&next,oldhead,(void*)newhead));

'next' is the freelist's head,the function will put 'next' point to newhead, and nexhead->next point to original next,butI found sometimes newhead->next doesn't update with 'next'

is it relevant to memory fence?

BTW, I only tested it with gcc

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