[PATCH V5] riscv: Add qspinlock support

[Arnd Bergmann]

On Mon, Jun 20, 2022 at 5:54 PM <guoren at kernel.org> wrote:
> >+config RISCV_USE_QUEUED_SPINLOCKS
> +       bool "Using queued spinlock instead of ticket-lock"

Maybe we can just make ARCH_USE_QUEUED_SPINLOCKS
user visible and give users the choice between the two generic
implementations across all architectures that support the qspinlock
variant.

In arch/riscv, you'd then just have a

        select ARCH_HAVE_QUEUED_SPINLOCKS

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
> +

Along the same lines:

I think I'd prefer the header changes to be done in the asm-generic
version of this file, so this can be shared across all architectures
that want to give the choice between ticket and queued spinlock.

        Arnd