On Mon, Dec 21, 2020 at 10:04 AM Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote: > > Hello, > > On Sat, Dec 19, 2020 at 09:08:55PM -0800, Andy Lutomirski wrote: > > On Sat, Dec 19, 2020 at 6:49 PM Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote: > > > The ptes are changed always with the PT lock, in fact there's no > > > problem with the PTE updates. The only difference with mprotect > > > runtime is that the mmap_lock is taken for reading. And the effect > > > contested for this change doesn't affect the PTE, but supposedly the > > > tlb flushing deferral. > > > > Can you point me at where the lock ends up being taken in this path? > > pte_offset_map_lock in change_pte_range, as in mprotect, no difference. > > As I suspected on my follow up, the bug described wasn't there, but > I'll look at the new theory posted. Indeed.
