On Mon, Nov 25, 2013 at 02:29:03PM +0800, Xiao Guangrong wrote: > >> Also, there is no guarantee of termination (as long as sptes are > >> deleted with the correct timing). BTW, can't see any guarantee of > >> termination for rculist nulls either (a writer can race with a lockless > >> reader indefinately, restarting the lockless walk every time). > > > > Hmm, that can be avoided by checking dirty-bitmap before rewalk, > > that means, if the dirty-bitmap has been set during lockless > > write-protection, > > it�s unnecessary to write-protect its sptes. Your idea? > This idea is based on the fact that the number of rmap is limited by > RMAP_RECYCLE_THRESHOLD. So, in the case of adding new spte into rmap, > we can break the rewalk at once, in the case of deleting, we can only > rewalk RMAP_RECYCLE_THRESHOLD times.
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