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uprobes: Suppress uprobe_munmap() from mmput()

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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.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182231.GA20336@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Oleg Nesterov 2012-07-29 20:22:31 +02:00 committed by Ingo Molnar
parent 665605a2a2
commit 2fd611a991
1 changed files with 3 additions and 0 deletions
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3
kernel/events/uprobes.c
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@ -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;