Okay
On Mon, Jun 20, 2022 at 11:58 PM <Conor.Dooley@xxxxxxxxxxxxx> wrote:
>
>
>
> On 20/06/2022 16:54, guoren@xxxxxxxxxx wrote:
> > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> >
> > Enable qspinlock and meet the requirements mentioned in a8ad07e5240c9
> > ("asm-generic: qspinlock: Indicate the use of mixed-size atomics").
> >
> > - RISC-V atomic_*_release()/atomic_*_acquire() are implemented with
> > own relaxed version plus acquire/release_fence for RCsc
> > synchronization.
> >
> > - RISC-V LR/SC pairs could provide a strong/weak forward guarantee
> > that depends on micro-architecture. And RISC-V ISA spec has given
> > out several limitations to let hardware support strict forward
> > guarantee (RISC-V User ISA - 8.3 Eventual Success of
> > Store-Conditional Instructions). Some riscv cores such as BOOMv3
> > & XiangShan could provide strict & strong forward guarantee (The
> > cache line would be kept in an exclusive state for Backoff cycles,
> > and only this core's interrupt could break the LR/SC pair).
> >
> > - RISC-V could provide cheap atomic_fetch_or_acquire() with RCsc.
> >
> > - RISC-V only provides relaxed xhg16 to support qspinlock.
> >
> > The first version of patch was made in 2019.1 [1]. The second version
> > was made in 2020.11 [2].
> >
> > [1] https://lore.kernel.org/linux-riscv/20190211043829.30096-1-michaeljclark@xxxxxxx/#r
> > [2] https://lore.kernel.org/linux-riscv/1606225437-22948-2-git-send-email-guoren@xxxxxxxxxx/
> >
> > Change V5:
> > - Update comment with RISC-V forward guarantee feature.
> > - Back to V3 direction and optimize asm code.
> >
> > Change V4:
> > - Remove custom sub-word xchg implementation
> > - Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32 in locking/qspinlock
> >
> > Change V3:
> > - Coding convention by Peter Zijlstra's advices
> >
> > Change V2:
> > - Coding convention in cmpxchg.h
> > - Re-implement short xchg
> > - Remove char & cmpxchg implementations
>
> Hey,
> How come the changelog is inside the commit message?
> I assume its a copy paste error..
> Thanks,
> Conor.
>
> >
> > Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> > Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Cc: Waiman Long <longman@xxxxxxxxxx>
> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
> > Cc: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
> > ---
> > arch/riscv/Kconfig | 9 +++++++++
> > arch/riscv/include/asm/Kbuild | 4 ++--
> > arch/riscv/include/asm/cmpxchg.h | 16 ++++++++++++++++
> > arch/riscv/include/asm/spinlock.h | 12 ++++++++++++
> > arch/riscv/include/asm/spinlock_types.h | 12 ++++++++++++
> > 5 files changed, 51 insertions(+), 2 deletions(-)
> > create mode 100644 arch/riscv/include/asm/spinlock.h
> > create mode 100644 arch/riscv/include/asm/spinlock_types.h
> >
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 32ffef9f6e5b..3b0b117b4e95 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -333,6 +333,15 @@ config NODES_SHIFT
> > Specify the maximum number of NUMA Nodes available on the target
> > system. Increases memory reserved to accommodate various tables.
> >
> > +config RISCV_USE_QUEUED_SPINLOCKS
> > + bool "Using queued spinlock instead of ticket-lock"
> > + depends on SMP && MMU
> > + select ARCH_USE_QUEUED_SPINLOCKS
> > + default y if NUMA
> > + help
> > + Make sure your micro arch LL/SC has a strong forward progress guarantee.
> > + Otherwise, stay at ticket-lock.
> > +
> > config RISCV_ALTERNATIVE
> > bool
> > depends on !XIP_KERNEL
> > diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
> > index 504f8b7e72d4..e066ccab6417 100644
> > --- a/arch/riscv/include/asm/Kbuild
> > +++ b/arch/riscv/include/asm/Kbuild
> > @@ -2,10 +2,10 @@
> > generic-y += early_ioremap.h
> > generic-y += flat.h
> > generic-y += kvm_para.h
> > +generic-y += mcs_spinlock.h
> > generic-y += parport.h
> > -generic-y += spinlock.h
> > -generic-y += spinlock_types.h
> > generic-y += qrwlock.h
> > generic-y += qrwlock_types.h
> > +generic-y += qspinlock.h
> > generic-y += user.h
> > generic-y += vmlinux.lds.h
> > diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h
> > index 12debce235e5..f7f8e359d3ac 100644
> > --- a/arch/riscv/include/asm/cmpxchg.h
> > +++ b/arch/riscv/include/asm/cmpxchg.h
> > @@ -17,6 +17,22 @@
> > __typeof__(new) __new = (new); \
> > __typeof__(*(ptr)) __ret; \
> > switch (size) { \
> > + case 2: \
> > + u32 temp; \
> > + u32 shif = ((ulong)__ptr & 2) ? 16 : 0; \
> > + u32 mask = 0xffff << shif; \
> > + __ptr = (__typeof__(ptr))((ulong)__ptr & ~(ulong)2); \
> > + __asm__ __volatile__ ( \
> > + "0: lr.w %0, %2\n" \
> > + " and %1, %0, %z3\n" \
> > + " or %1, %1, %z4\n" \
> > + " sc.w %1, %1, %2\n" \
> > + " bnez %1, 0b\n" \
> > + : "=&r" (__ret), "=&r" (temp), "+A" (*__ptr) \
> > + : "rJ" (~mask), "rJ" (__new << shif) \
> > + : "memory"); \
> > + __ret = (__ret & mask) >> shif; \
> > + break; \
> > case 4: \
> > __asm__ __volatile__ ( \
> > " amoswap.w %0, %2, %1\n" \
> > diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h
> > new file mode 100644
> > index 000000000000..fd3fd09cff52
> > --- /dev/null
> > +++ b/arch/riscv/include/asm/spinlock.h
> > @@ -0,0 +1,12 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef __ASM_SPINLOCK_H
> > +#define __ASM_SPINLOCK_H
> > +
> > +#ifdef CONFIG_ARCH_USE_QUEUED_SPINLOCKS
> > +#include <asm/qspinlock.h>
> > +#include <asm/qrwlock.h>
> > +#else
> > +#include <asm-generic/spinlock.h>
> > +#endif
> > +
> > +#endif /* __ASM_SPINLOCK_H */
> > diff --git a/arch/riscv/include/asm/spinlock_types.h b/arch/riscv/include/asm/spinlock_types.h
> > new file mode 100644
> > index 000000000000..9281237b5f4e
> > --- /dev/null
> > +++ b/arch/riscv/include/asm/spinlock_types.h
> > @@ -0,0 +1,12 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef __ASM_SPINLOCK_TYPES_H
> > +#define __ASM_SPINLOCK_TYPES_H
> > +
> > +#ifdef CONFIG_ARCH_USE_QUEUED_SPINLOCKS
> > +#include <asm-generic/qspinlock_types.h>
> > +#include <asm-generic/qrwlock_types.h>
> > +#else
> > +#include <asm-generic/spinlock_types.h>
> > +#endif
> > +
> > +#endif /* __ASM_SPINLOCK_TYPES_H */
--
Best Regards
Guo Ren
ML: https://lore.kernel.org/linux-csky/
