lkml.org 
[lkml]   [2020]   [Dec]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 1/2] futex: mark futex_detect_cmpxchg() as 'noinline'
    On Tue, Dec 15, 2020 at 12:26:10PM +0100, Arnd Bergmann wrote:
    > On Tue, Dec 15, 2020 at 7:09 AM Guo Ren <guoren@kernel.org> wrote:
    > > On Mon, Dec 14, 2020 at 9:15 PM Arnd Bergmann <arnd@kernel.org> wrote:
    > > > I had a look at what other architectures always implement
    > > > futex_atomic_cmpxchg_inatomic() or can use the asm-generic non-SMP version,
    > > > and I found that it's pretty much all of them, the odd ones being just sparc32
    > > > and csky, which use asm-generic/futex.h but do have an SMP option,
    > > > as well as xtensa
    > > >
    > > > I would guess that for csky, this is a mistake, as the architecture is fairly
    > > > new and should be able to implement it. Not sure about sparc32.
    > >
    > > The c610, c807, c810 don't support SMP, so futex_cmpxchg_enabled = 1
    > > with asm-generic's implementation.
    > > For c860, there is no HAVE_FUTEX_CMPXCHG and cmpxchg_inatomic/inuser
    > > implementation, so futex_cmpxchg_enabled = 0.
    > >
    > > Thx for point it out, we'll implement cmpxchg_inatomic/inuser for C860
    > > and still use asm-generic for non-smp CPUs.
    >
    > Sounds good to me.
    >
    > With that, I would suggest we actually remove the -ENOSYS fallback
    > for arch_futex_atomic_op_inuser() and futex_atomic_cmpxchg_inatomic()
    > in asm-generic/futex.h as well as the HAVE_FUTEX_CMPXCHG Kconfig
    > symbol, plus these additional fixups:
    >
    > - for xtensa and mips configurations without ll/sc, fall back to the
    > asm-generic version. These are all uniprocessor, while the
    > corresponding SMP machines have a working
    > arch_futex_atomic_op_inuser().
    >
    > - Disable SMP support for sun4m/sun4d. From the historic git
    > tree, it's unclear how well this ever worked, and very few machines
    > of this class ever existed

    Hooray!! what about PA-RISC ? Can we burn that too?

    \
     
     \ /
      Last update: 2020-12-16 12:44    [W:2.973 / U:1.260 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site