On Mon, Jan 21, 2019 at 01:10:39PM +0200, Mike Rapoport wrote: > On Mon, Jan 21, 2019 at 03:57:18PM +0800, Peter Xu wrote: > > It does not make sense to try to wake up any waiting thread when we're > > write-protecting a memory region. Only wake up when resolving a write > > protected page fault. > > Probably it would be better to make it default to wake up only when > requested explicitly? Yes, I think that's what this series does? Now when we do UFFDIO_WRITEPROTECT with !WP and !DONTWAKE then we'll first resolve the page fault, then wake up the process properly. And we request that explicity using !WP and DONTWAKE. Or did I misunderstood the question? > Then we can simply disallow _DONTWAKE for uffd_wp and only use > UFFDIO_WRITEPROTECT_MODE_WP as possible mode. I'd admit I don't know the major usage of DONTWAKE (and I'd be glad to know...), however since we have this flag for both UFFDIO_COPY and UFFDIO_ZEROCOPY, then it seems sane to have DONTWAKE for WRITEPROTECT too? Or is there any other explicit reason to omit it? Thanks! -- Peter Xu