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? -- Darren Hart Intel Open Source Technology Center -- 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
