On Sat, Jul 4, 2020 at 12:34 AM Pavel Machek <pavel@xxxxxx> wrote: > On Fri 2020-07-03 15:29:22, Jann Horn wrote: > > On Fri, Jul 3, 2020 at 1:30 PM Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > On Fri 03-07-20 10:34:09, Catangiu, Adrian Costin wrote: > > > > This patch adds logic to the kernel power code to zero out contents of > > > > all MADV_WIPEONSUSPEND VMAs present in the system during its transition > > > > to any suspend state equal or greater/deeper than Suspend-to-memory, > > > > known as S3. > > > > > > How does the application learn that its memory got wiped? S2disk is an > > > async operation and it can happen at any time during the task execution. > > > So how does the application work to prevent from corrupted state - e.g. > > > when suspended between two memory loads? > > > > You can do it seqlock-style, kind of - you reserve the first byte of > > the page or so as a "is this page initialized" marker, and after every > > read from the page, you do a compiler barrier and check whether that > > byte has been > > That would also need smp cpu barriers, and guarantee that first byte > is always ... cleared first, and matching barriers in kernel space, > too, no? Not if it happens in the guts of the suspend stuff, when userspace is frozen, I think?
