Re: [PATCH] [13/16] POISON: The high level memory error handler in the VM

Andi Kleen
2009-04-07T19:38:29Z

On Tue, Apr 07, 2009 at 08:51:46PM +0200, Johannes Weiner wrote:
> > +
> > + if (av == NULL) /* Not actually mapped anymore */
> > + goto out;
> > +
> > + read_lock(&tasklist_lock);
> > + for_each_process (tsk) {
> > + if (!tsk->mm)
> > + continue;
> > + list_for_each_entry (vma, &av->head, anon_vma_node) {
> > + if (vma->vm_mm == tsk->mm)
> > + add_to_kill(tsk, page, vma, to_kill, tkc);
> > + }
> > + }
> > + read_unlock(&tasklist_lock);
> > +out:
> > + page_unlock_anon_vma(av);
>
> If !av, this doesn't need an unlock and in fact crashes due to
> dereferencing NULL.

Good point. Fixed. Thanks.
>
> > +static int poison_page_prepare(struct page *p, unsigned long pfn, int trapno)
> > +{
> > + if (PagePoison(p)) {
> > + printk(KERN_ERR
> > + "MCE: Error for already poisoned page at %lx\n", pfn);
> > + return -1;
> > + }
> > + SetPagePoison(p);
>
> TestSetPagePoison()?

It doesn't matter in this case because it doesn't need to be atomic.
The normal reason for TestSet is atomicity requirements. If someone
feels strongly about it I can add it.

-Andi

--
ak@linux.intel.com -- Speaking for myself only.