On 11/5/19 6:56 AM, Thomas Gleixner wrote: > On Tue, 5 Nov 2019, Florian Weimer wrote: >> * Thomas Gleixner: >>> On Tue, 5 Nov 2019, Florian Weimer wrote: >>>> * Shawn Landden: >>>>> If this new ABI is used, then bit 1 of the *next pointer of the >>>>> user-space robust_list indicates that the futex_offset2 value should >>>>> be used in place of the existing futex_offset. >>>> >>>> The futex interface currently has some races which can only be fixed by >>>> API changes. I'm concerned that we sacrifice the last bit for some >>>> rather obscure feature. What if we need that bit for fixing the >>>> correctness issues? >>> >>> That current approach is going nowhere and if we change the ABI ever then >>> this needs to happen with all *libc folks involved and agreeing. >>> >>> Out of curiosity, what's the race issue vs. robust list which you are >>> trying to solve? >> >> Sadly I'm not trying to solve them. Here's one of the issues: >> >> <https://sourceware.org/bugzilla/show_bug.cgi?id=14485> > > That one seems more a life time problem, i.e. the mutex is destroyed, > memory freed and map address reused while another thread was not yet out of > the mutex_unlock() call. Nasty. It is difficult to fix. The other issue is this: "Robust mutexes do not take ROBUST_LIST_LIMIT into account" https://sourceware.org/bugzilla/show_bug.cgi?id=19089 -- Cheers, Carlos.
