On Mon 29-02-16 20:02:09, Vladimir Davydov wrote: > An mm_struct may be pinned by a file. An example is vhost-net device > created by a qemu/kvm (see vhost_net_ioctl -> vhost_net_set_owner -> > vhost_dev_set_owner). If such process gets OOM-killed, the reference to > its mm_struct will only be released from exit_task_work -> ____fput -> > __fput -> vhost_net_release -> vhost_dev_cleanup, which is called after > exit_mmap, where TIF_MEMDIE is cleared. As a result, we can start > selecting the next victim before giving the last one a chance to free > its memory. In practice, this leads to killing several VMs along with > the fattest one.
I am wondering why our PF_EXITING protection hasn't fired up. This is not done in the mmotm tree but I guess you have seen the issue with the linus tree, right? Do you have a log with oom reports available? To be honest I do not feel very comfortable about moving the exit_oom_victim even further down in do_exit path behind even less clear locking or other dependencies. Let's see if we can do any better for this particular case. > Signed-off-by: Vladimir Davydov <[email protected]> > --- > kernel/exit.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/exit.c b/kernel/exit.c > index fd90195667e1..cc50e12165f7 100644 > --- a/kernel/exit.c > +++ b/kernel/exit.c > @@ -434,8 +434,6 @@ static void exit_mm(struct task_struct *tsk) > task_unlock(tsk); > mm_update_next_owner(mm); > mmput(mm); > - if (test_thread_flag(TIF_MEMDIE)) > - exit_oom_victim(tsk); > } > > static struct task_struct *find_alive_thread(struct task_struct *p) > @@ -746,6 +744,8 @@ void do_exit(long code) > disassociate_ctty(1); > exit_task_namespaces(tsk); > exit_task_work(tsk); > + if (test_thread_flag(TIF_MEMDIE)) > + exit_oom_victim(tsk); > exit_thread(); > > /* > -- > 2.1.4 -- Michal Hocko SUSE Labs
