On Fri, 16 Jan 2015, Darren Hart wrote: > On 1/16/15, 12:54 PM, "Michael Kerrisk (man-pages)" > <mtk.manpages@xxxxxxxxx> wrote: > > >On 01/16/2015 04:20 PM, Thomas Gleixner wrote: > >> On Fri, 16 Jan 2015, Michael Kerrisk (man-pages) wrote: > >> > >>> Hello Thomas, > >>> > >>> On 01/15/2015 11:23 PM, Thomas Gleixner wrote: > >>>> On Thu, 15 Jan 2015, Michael Kerrisk (man-pages) wrote: > >>>>>> [EINVAL] uaddr equal uaddr2. Requeue to same futex. > >>>>> > >>>>> ??? I added this, but does this error not occur only for PI requeues? > >>>> > >>>> It's equally wrong for normal futexes. And its actually the same code > >>>> checking for this for all variants. > >>> > >>> I don't understand "equally wrong" in your reply, I'm sorry. Do you > >>> mean: > >>> > >>> a) This error text should be there for both normal and PI requeues > >> > >> It is there for both. The requeue code has that check independent of > >> the requeue type (normal/pi). It never makes sense to requeue > >> something to itself whether normal or pi futex. We added this for PI, > >> because there it is harmful, but we did not special case it. So normal > >> futexes get the same treatment. > > > >Hello Thomas, > > > >Color me stupid, but I can't see this in futex_requeue(). Where is that > >check that is "independent of the requeue type (normal/pi)"? > > > >When I look through futex_requeue(), all the likely looking sources > >of EINVAL are governed by a check on the 'requeue_pi' argument. > > > Right, in the non-PI case, I believe there are valid use cases: move to > the back of the FIFO, for example (OK, maybe the only example?). Both > tests ensuring uaddr1 != uaddr2 are under the requeue_pi conditional > block. The second compares the keys in case they are not FUTEX_PRIVATE > (uaddrs would be different, but still the same backing store). > > Thomas, am I missing a test for this someplace else? No, I had a short look at the code misread it. So, yes, it's a valid operation for the non PI case. Sorry for the confusion. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
