> On Sep 28, 2018, at 1:42 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > >> On Fri, 28 Sep 2018, Martin Schwidefsky wrote: >> On Fri, 28 Sep 2018 09:12:10 +0200 >> Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: >>> I don't know if that has happened, and whether it would work on s390 now. >> >> commit 03b8c7b623c80af264c4c8d6111e5c6289933666 >> Author: Heiko Carstens <heiko.carstens@xxxxxxxxxx> >> Date: Sun Mar 2 13:09:47 2014 +0100 >> >> futex: Allow architectures to skip futex_atomic_cmpxchg_inatomic() test >> >> If an architecture has futex_atomic_cmpxchg_inatomic() implemented and there >> is no runtime check necessary, allow to skip the test within futex_init(). >> >> This allows to get rid of some code which would always give the same result, >> and also allows the compiler to optimize a couple of if statements away. >> >> Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx> >> Cc: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx> >> Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> >> Link: http://lkml.kernel.org/r/20140302120947.GA3641@osiris >> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> >> >> >> Heiko created the CONFIG_HAVE_FUTEX_CMPXCHG to get around this issue. >> We just skip the runtime check as well as arc, m68k and sh. Not sure >> about xtensa, the set it config option only for !MMU. > > Duh. grep would have told me. -ENOTENOUGHCOFFEE > > There’s another way to skin this cat: keep KERNEL_DS but pass a valid pointer. I don’t suppose you remember why you didn’t do that?
