Messages in this thread | | | Subject | Re: memory barrier question | From | Benjamin Herrenschmidt <> | Date | Sat, 18 Sep 2010 07:49:08 +1000 |
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> Right but in the concrete namei example I can't see how a compiler > optimization can make a difference. The order of the loads is quite > clear: > > LOAD inode = next.dentry->inode > if (inode != NULL) > LOAD inode->f_op > > What is there the compiler can optimize?
Those two loads depend on each other, I don't think any implementation can re-order them. In fact, such data dependency is typically what is used to avoid having barriers in some cases. The second load cannot be issued until the value from the first one is returned.
Cheers, Ben.
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