On Thu, Jul 27, 2017 at 10:53:12AM +0200, Peter Zijlstra wrote: > Another crazy idea is using madvise() for this. The new MADV_MEMBAR > could revoke PROT_WRITE and PROT_READ for all extant PTEs. Then the > tasks attempting access will fault and the fault handler can figure out > if it still needs to issue a MB or not before reinstating the PTE.
Slight oversight is that page-tables are per process and we need a MB per thread, so the fault handler can simply issue a private sys_membarrier() to spread the joy around the local process. > That is fully contained to the tasks actually having that map, and > doesn't perturb anybody else.
