Messages in this thread | | | Date | Thu, 12 Jul 2012 11:27:51 +0530 | From | Srikar Dronamraju <> | Subject | Re: [PATCH 2/5] uprobes: suppress uprobe_munmap() from mmput() |
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* Oleg Nesterov <oleg@redhat.com> [2012-07-08 22:30:03]:
> uprobe_munmap() does get_user_pages() and it is also called from > the final mmput()->exit_mmap() path. This slows down exit/mmput() > for no reason, and I think it is simply dangerous/wrong to try to > fault-in a page into the dying mm. If nothing else, this happens > after the last sync_mm_rss(), afaics handle_mm_fault() can change > the task->rss_stat and make the subsequent check_mm() unhappy. > > Change uprobe_munmap() to check mm->mm_users != 0. > > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> --- > kernel/events/uprobes.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index a93b6df..47c4e24 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -1082,6 +1082,9 @@ void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned lon > if (!atomic_read(&uprobe_events) || !valid_vma(vma, false)) > return; > > + if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */ > + return; > + > if (!atomic_read(&vma->vm_mm->uprobes_state.count)) > return; > > -- > 1.5.5.1 >
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