Commit 2fd611a9 authored Jul 29, 2012 by Oleg Nesterov Committed by Ingo Molnar Jul 30, 2012

uprobes: Suppress uprobe_munmap() from mmput()



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>

parent 665605a2

kernel/events/uprobes.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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;

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