lkml.org 
[lkml]   [2017]   [Dec]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH 1/1] futex: futex_wake_op, fix sign_extend32 sign bits
    From
    Date
    On 12/10/2017, 09:50 PM, Linus Torvalds wrote:
    > On Thu, Nov 30, 2017 at 6:35 AM, Jiri Slaby <jslaby@suse.cz> wrote:
    >> sign_extend32 counts the sign bit parameter from 0, not from 1. So we
    >> have to use "11" for 12th bit, not "12".
    >
    > This interface is crap. It really doesn't make much sense. I wonder
    > how many people have gotten this wrong, but it's hard to tell.

    I tend to agree, because it really surprised me. So at that time I
    searched for most (all?) uses of the interface, checked them and all of
    them *seem* to be fine.

    > I'm applying this directly to my tree since I didn't see anybody else
    > react to it, but the whole pattern worries me.
    >
    > Also, clearly nobody actually uses the odder corners of futex ops
    > anyway. Maybe we should deprecate them entirely?
    >
    > Jiri, did you notice by testing, or what?

    I noticed it by coincidence while fixing the strace build test failures
    -- e78c38f6bdd9 (futex: futex_wake_op, do not fail on invalid op). I
    compiled a bit modified futex_atomic_op_inuser in userspace to test the
    conversion and the added check and it did not work.

    And yes, somebody (tglx?) noted already that this interface is old and
    perhaps unused.

    thanks,
    --
    js
    suse labs

    \
     
     \ /
      Last update: 2017-12-11 08:38    [W:3.033 / U:0.780 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site