On 11/12/2017 23:11, David Rientjes wrote:
> Commit 4d4bbd8526a8 ("mm, oom_reaper: skip mm structs with mmu notifiers")
> prevented the oom reaper from unmapping private anonymous memory with the
> oom reaper when the oom victim mm had mmu notifiers registered.
>
> The rationale is that doing mmu_notifier_invalidate_range_{start,end}()
> around the unmap_page_range(), which is needed, can block and the oom
> killer will stall forever waiting for the victim to exit, which may not
> be possible without reaping.
>
> That concern is real, but only true for mmu notifiers that have blockable
> invalidate_range_{start,end}() callbacks. This patch adds a "flags" field
> for mmu notifiers that can set a bit to indicate that these callbacks do
> block.
Why not put the flag in the ops, since the same ops should always be
either blockable or unblockable?
Paolo
> The implementation is steered toward an expensive slowpath, such as after
> the oom reaper has grabbed mm->mmap_sem of a still alive oom victim.
>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
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