On Fri, Jan 15, 2016 at 3:51 PM, Alex Bennée <alex.ben...@linaro.org> wrote: > > alvise rigo <a.r...@virtualopensystems.com> writes: > >> This problem could be related to a missing multi-threaded aware >> translation of the atomic instructions. >> I'm working on this missing piece, probably the next week I will >> publish something. > > Maybe. We still have Fred's: > > Use atomic cmpxchg to atomically check the exclusive value in a STREX > > Which I think papers over the cracks for both arm and aarch64 in MTTCG > while not being as correct as your work.
Keep in mind that Linux on arm64 uses the LDXP/STXP instructions that exist solely in aarch64. These instructions are purely emulated now and can potentially write 128 bits of data in a non-atomic fashion. Regards, alvise > >> >> Regards, >> alvise >> >> On Fri, Jan 15, 2016 at 3:24 PM, Pranith Kumar <bobby.pr...@gmail.com> wrote: >>> Hi Alex, >>> >>> On Fri, Jan 15, 2016 at 8:53 AM, Alex Bennée <alex.ben...@linaro.org> wrote: >>>> Can you try this branch: >>>> >>>> >>>> https://github.com/stsquad/qemu/tree/mttcg/multi_tcg_v8_wip_ajb_fix_locks-r1 >>>> >>>> I think I've caught all the things likely to screw up addressing. >>>> >>> >>> I tried this branch and the boot hangs like follows: >>> >>> [ 2.001083] random: systemd-udevd urandom read with 1 bits of entropy >>> available >>> main-loop: WARNING: I/O thread spun for 1000 iterations >>> [ 23.778970] INFO: rcu_sched detected stalls on CPUs/tasks: {} (detected >>> by 0, t=2102 jiffies, g=-165, c=-166, q=83) > > This is just saying the kernel has been waiting for a while and nothing > has happened. > >>> I will try to debug and see where it is hanging. > > If we knew what the kernel was waiting for that would be useful to know. > >>> >>> Thanks! >>> -- >>> Pranith > > > -- > Alex Bennée