Messages in this thread | | | Subject | Re: [PATCH v2] futex: Fix regression with read only mappings | From | Peter Zijlstra <> | Date | Mon, 27 Jun 2011 20:15:59 +0200 |
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On Mon, 2011-06-27 at 11:40 -0500, Shawn Bohrer wrote: > > > if (PageAnon(page_head)) { > > > > This bit needs a comment too (unless I am the only one to whom this > was > > non-obvious), maybe: > > > > > > /* > > * A read-only anonymous page implies a COW on a > > * MAP_PRIVATE mapping. There is no sane use-case > > * for this scenario, return -EFAULT to userspace. > > */ > > Your comment is wrong. Unfortunately the code is completly > non-obvious to me as well, and I have no idea why it is there. This > little snippet came from Peter's suggested fix in: > > https://lkml.org/lkml/2011/6/6/368 > > Sadly Peter's gone silent and I'm left wondering if he knew some > corner case that should return -EFAULT with a RO anonymous page or if > he _thought_ this was preventing RO MAP_PRIVATE mappings. If it is > the latter then this block can be removed because it does NOT do that. > > > + if (ro) { > > > + err = -EFAULT; > > > + goto out; > > > + } > > > +
Peter simply gets too much email.. anyway, the reason I put that there is that a RO Anon page will never change and is thus a little pointless to use for futex ops.
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