Messages in this thread | | | Date | Mon, 11 Oct 1999 17:40:52 -0400 (EDT) | From | Alexander Viro <> | Subject | Re: locking question: do_mmap(), do_munmap() |
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On Mon, 11 Oct 1999, Stephen C. Tweedie wrote:
> Hi, > > On Mon, 11 Oct 1999 12:05:23 -0400 (EDT), Alexander Viro > <viro@math.psu.edu> said: > > > On Mon, 11 Oct 1999, Stephen C. Tweedie wrote: > >> No, spinlocks would be ideal. The vma swapout codes _have_ to be > >> prepared for the vma to be destroyed as soon as we sleep. In fact, the > >> entire mm may disappear if the process happens to exit. Once we know > >> which page to write where, the swapout operation becomes a per-page > >> operation, not per-vma. > > > Aha, so you propose to drop it in ->swapout(), right? (after get_file() in > > filemap_write_page()... Ouch. Probably we'ld better lambda-expand the call > > in filemap_swapout() - the thing is called from other places too)... > > Right now it is the big kernel lock which is used for this, and the > scheduler drops it anyway for us. If anyone wants to replace that lock > with another spinlock, then yes, the swapout method would have to drop > it before doing anything which could block. And that is ugly: having > spinlocks unbalanced over function calls is a maintenance nightmare.
Agreed, but the big lock does not (and IMHO should not) cover the vma list modifications.
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