Messages in this thread | | | Date | Mon, 11 Jan 1999 12:20:39 +0100 | From | Pavel Machek <> | Subject | Re: MM deadlock [was: Re: arca-vm-8...] |
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Hi!
> In fact, to make it really safe we'd need to avoid synchronous swapout > altogether: otherwise we can have > > A kswiod nbd server process > lock_super(); > bread(ndb device); > try_to_free_page(); > rw_swap_page_async(); > filemap_write_page(); > lock_super(); > wait_on_buffer(); > try_to_free_page(); > rw_swap_page_sync(); > Oops, kswiod is stalled. > > Can we get away without synchronous swapout? Notice that in this case, > kswiod may be blocked but kswapd itself will not be. As long as the nbd > server does not try to do a synchronous swap, it won't deadlock on > kswiod. In other words, it is safe to wait for avaibility of > another
Is this only matter of nbd? If so, maybe the best solution is to start claiming: "don't swap over nbd, don't mount localhost drives read write". [It is bad, but it is probably better than polluting rest of kernel with nbd workarounds...]
Pavel -- The best software in life is free (not shareware)! Pavel GCM d? s-: !g p?:+ au- a--@ w+ v- C++@ UL+++ L++ N++ E++ W--- M- Y- R+
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