On Thu, Dec 05, 2013 at 11:30:27PM +0800, Xiao Guangrong wrote: > In some cases, the lockless walker will do endless-walking on desc and > without rewalk, consider this case: > > there are two descs: desc1 and desc2 who is pointed by desc1->next： > desc1->next = desc2. > > CPU 0 > CPU 1 > > lockless walk on desc1 > deleting > desc1 from the rmap > lockless walk on desc2 (desc1->next) > delete desc2 > from the rmap > add desc1 > add desc2, > then desc2->next = desc1 > > lockless walk on desc1 > delete desc2 > delete desc1 > add desc2 > add desc1; the > desc1->next = desc2 > lockless walk on desc2 > > …… > > Then, the walker is endlessly walking on desc1 and desc2 without any rewalk.
The counter can be local to the walker. If its more than maximum rmap size, break. (but still, please consider carefully whether lockless list walking is really necessary or can be avoided). -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
