On Wed, Mar 24, 2021 at 05:58:58PM +0530, Anup Patel wrote: > On Wed, Mar 24, 2021 at 3:45 PM <guo...@kernel.org> wrote: > > > > From: Guo Ren <guo...@linux.alibaba.com> > > > > This patch introduces a ticket lock implementation for riscv, along the > > same lines as the implementation for arch/arm & arch/csky. > > > > Signed-off-by: Guo Ren <guo...@linux.alibaba.com> > > Cc: Catalin Marinas <catalin.mari...@arm.com> > > Cc: Will Deacon <will.dea...@arm.com> > > Cc: Peter Zijlstra <pet...@infradead.org> > > Cc: Palmer Dabbelt <palmerdabb...@google.com> > > Cc: Anup Patel <a...@brainfault.org> > > Cc: Arnd Bergmann <a...@arndb.de> > > --- > > arch/riscv/Kconfig | 1 + > > arch/riscv/include/asm/Kbuild | 1 + > > arch/riscv/include/asm/spinlock.h | 158 > > ++++++++++++-------------------- > > arch/riscv/include/asm/spinlock_types.h | 19 ++-- > > NACK from myside. > > Linux ARM64 has moved away from ticket spinlock to qspinlock. > > We should directly go for qspinlock.
I think it is a sensible intermediate step, even if you want to go qspinlock. Ticket locks are more or less trivial and get you fairness and all that goodness without the mind bending complexity of qspinlock. Once you have the ticket lock implementation solid (and qrwlock) and everything, *then* start to carefully look at qspinlock. Now, arguably arm64 did the heavy lifting of making qspinlock good on weak architectures, but if you want to do it right, you still have to analyze the whole thing for your own architecture.