On Tue, 24 Apr 2018, Michal Hocko wrote: > > I wanted to remove all per task checks because they are now irrelevant: > > this would be the first dependency that exit_mmap() has on any > > task_struct, which isn't intuitive -- we simply want to exit the mmap. > > There's no requirement that current owns the mm other than this. > > There is no such requirement in the __oom_reap_task_mm. The given task > is used for reporting purposes. > And tracing, which is pointless. And it unnecessarily spams the kernel log for basic exiting. > > I wanted > > to avoid the implicit dependency on MMF_OOM_SKIP and make it explicit in > > the exit path to be matched with the oom reaper. > > Well, I find it actually better that the code is not explicit about > MMF_OOM_SKIP. The whole thing happens in the oom proper which should be > really preferable. The whole synchronization is then completely > transparent to the oom (including the oom lock etc). > It's already done in exit_mmap(). I'm not changing > > I didn't want anything > > additional printed to the kernel log about oom reaping unless the > > oom_reaper actually needed to intervene, which is useful knowledge outside > > of basic exiting. > > Can we shave all those parts as follow ups and make the fix as simple as > possible? > It is as simple as possible. It is not doing any unnecessary locking or checks that the exit path does not need to do for the sake of a smaller patch. The number of changed lines in the patch is not what I'm interested in, I am interested in something that is stable, something that works, doesn't add additional (and unnecessary locking), and doesn't change around what function sets what bit when called from what path. > > My patch has passed intensive testing on both x86 and powerpc, so I'll ask > > that it's pushed for 4.17-rc3. Many thanks to Tetsuo for the suggestion > > on calling __oom_reap_task_mm() from exit_mmap(). > > Yeah, but your patch does have a problem with blockable mmu notifiers > IIUC. What on earth are you talking about? exit_mmap() does mmu_notifier_release(). There are no blockable mmu notifiers.
