On Mon, 23 Aug 2010, Andrew Morton wrote:
> > --- a/fs/proc/base.c
> > +++ b/fs/proc/base.c
> > @@ -1047,6 +1047,21 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
> > return -EACCES;
> > }
> >
> > + task_lock(task);
> > + if (!task->mm) {
> > + task_unlock(task);
> > + unlock_task_sighand(task, &flags);
> > + put_task_struct(task);
> > + return -EINVAL;
> > + }
> > +
> > + if (oom_adjust != task->signal->oom_adj) {
> > + if (oom_adjust == OOM_DISABLE)
> > + atomic_inc(&task->mm->oom_disable_count);
> > + if (task->signal->oom_adj == OOM_DISABLE)
> > + atomic_dec(&task->mm->oom_disable_count);
> > + }
>
> scary function. Wanna try converting oom_adjust_write() to the
> single-exit-with-goto model sometime, see if the result looks more
> maintainable?
>
Ok, that would certainly be better.
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -65,6 +65,7 @@
> > #include <linux/perf_event.h>
> > #include <linux/posix-timers.h>
> > #include <linux/user-return-notifier.h>
> > +#include <linux/oom.h>
> >
> > #include <asm/pgtable.h>
> > #include <asm/pgalloc.h>
> > @@ -485,6 +486,7 @@ static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
> > mm->cached_hole_size = ~0UL;
> > mm_init_aio(mm);
> > mm_init_owner(mm, p);
> > + atomic_set(&mm->oom_disable_count, 0);
>
> So in fork() we zap this if !CLONE_VM? Was the CLONE_VM case tested
> nicely?
>
In clone(), yeah, fork() doesn't use CLONE_VM so the child thread will
always have a different ->mm. The new ->mm will get oom_disable_count
incremented later if tsk has inherited a OOM_DISABLE value.
We've been running with this patch (minus the sys_unshare() code I added)
for a year now internally.
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