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SubjectRe: [PATCH 0/7] microblaze: Define SMP safe operations
On Wed, Feb 12, 2020 at 05:08:52PM +0100, Peter Zijlstra wrote:
> On Wed, Feb 12, 2020 at 04:42:22PM +0100, Michal Simek wrote:
>
> > Microblaze has 32bit exclusive load/store instructions which should be used
> > instead of irq enable/disable. For more information take a look at
> > https://www.xilinx.com/support/documentation/sw_manuals/xilinx2019_2/ug984-vivado-microblaze-ref.pdf
> > starting from page 25.
>
> > arch/microblaze/include/asm/Kbuild | 1 -
> > arch/microblaze/include/asm/atomic.h | 265 ++++++++++++++++++-
> > arch/microblaze/include/asm/bitops.h | 189 +++++++++++++
> > arch/microblaze/include/asm/cmpxchg.h | 87 ++++++
> > arch/microblaze/include/asm/cpuinfo.h | 2 +-
> > arch/microblaze/include/asm/pgtable.h | 19 +-
> > arch/microblaze/include/asm/spinlock.h | 240 +++++++++++++++++
> > arch/microblaze/include/asm/spinlock_types.h | 25 ++
> > arch/microblaze/kernel/cpu/cache.c | 154 ++++++-----
> > arch/microblaze/kernel/cpu/cpuinfo.c | 38 ++-
> > arch/microblaze/kernel/cpu/mb.c | 207 ++++++++-------
> > arch/microblaze/kernel/timer.c | 2 +-
> > arch/microblaze/mm/consistent.c | 8 +-
> > 13 files changed, 1040 insertions(+), 197 deletions(-)
> > create mode 100644 arch/microblaze/include/asm/bitops.h
> > create mode 100644 arch/microblaze/include/asm/spinlock.h
> > create mode 100644 arch/microblaze/include/asm/spinlock_types.h
>
> I'm missing asm/barrier.h
>
> Also that PDF (thanks for that!), seems light on memory ordering
> details.
>
> Your comment:
>
> +/*
> + * clear_bit doesn't imply a memory barrier
> + */
>
> worries me, because that would imply your ll/sc does not impose order,
> but then you also don't have any explicit barriers in your locking
> primitives or atomics where required.
>
> In the PDF I only find MBAR; is that what smp_mb() ends up being?

Bah, I'm sure I did patches at some point that made
asm-generic/barrier.h #error if you didn't define at least one memory
barrier on CONFIG_SMP, but it seems that all got lost somewhere.


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