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the loss of a page modified (PG_M) bit in a race between processors. Quoting Tor: One scenario where the old code could cause a lost PG_M bit is a multithreaded linux program (or FreeBSD program using the linuxthreads port) where one thread was starting a subprocess. The thread doing fork() would call vmspace_fork(), which would then call vm_map_copy_entry() which would call pmap_protect() on an area possibly accessed by other threads. Additionally, make the clearing of PG_M by pmap_protect() unconditional if write permission is removed. Previously, PG_M could persist on a read-only unmanaged page. That seems inconsistent and confusing. In collaboration with: tegge@ MT5 candidate PR: 61852
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