On Wed, 2017-08-09 at 12:59 +0300, Kirill A. Shutemov wrote: > On Mon, Aug 07, 2017 at 10:59:51AM -0400, Rik van Riel wrote: > > On Mon, 2017-08-07 at 15:46 +0200, Michal Hocko wrote: > > > On Mon 07-08-17 15:22:57, Michal Hocko wrote: > > > > This is an user visible API so make sure you CC linux-api > > > > (added) > > > > > > > > On Sun 06-08-17 10:04:23, Rik van Riel wrote: > > > > > > > > > > A further complication is the proliferation of clone flags, > > > > > programs bypassing glibc's functions to call clone directly, > > > > > and programs calling unshare, causing the glibc > > > > > pthread_atfork > > > > > hook to not get called. > > > > > > > > > > It would be better to have the kernel take care of this > > > > > automatically. > > > > > > > > > > This is similar to the OpenBSD minherit syscall with > > > > > MAP_INHERIT_ZERO: > > > > > > > > > > https://man.openbsd.org/minherit.2 > > > > > > I would argue that a MAP_$FOO flag would be more appropriate. Or > > > do > > > you > > > see any cases where such a special mapping would need to change > > > the > > > semantic and inherit the content over the fork again? > > > > > > I do not like the madvise because it is an advise and as such it > > > can > > > be > > > ignored/not implemented and that shouldn't have any correctness > > > effects > > > on the child process. > > > > Too late for that. VM_DONTFORK is already implemented > > through MADV_DONTFORK & MADV_DOFORK, in a way that is > > very similar to the MADV_WIPEONFORK from these patches. > > It's not obvious to me what would break if kernel would ignore > MADV_DONTFORK or MADV_DONTDUMP. > You might end up with multiple processes having a device open which can only handle one process at a time. Another thing that could go wrong is that if overcommit_memory=2, a very large process with MADV_DONTFORK on a large memory area suddenly fails to fork (due to there not being enough available memory), and is unable to start a helper process. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
