Re: [PATCH v4 6/7] RISC-V: Move to queued RW locks

[Conor.Dooley]

On 30/04/2022 16:36, Palmer Dabbelt wrote:
> From: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
> 
> Now that we have fair spinlocks we can use the generic queued rwlocks,
> so we might as well do so.
> 
> Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>

Verbatim from the other patch:

I am loathe to add a TB tag since I have not done much by way of testing
any realistic use cases - but I have put it in our CI and have had a play
around with it locally & nothing obviously broke for me.

If you think that is sufficient:
Tested-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Otherwise feel free to ignore the tag.

Thanks,
Conor.
> ---
>   arch/riscv/Kconfig                      |  1 +
>   arch/riscv/include/asm/Kbuild           |  2 +
>   arch/riscv/include/asm/spinlock.h       | 99 -------------------------
>   arch/riscv/include/asm/spinlock_types.h | 24 ------
>   4 files changed, 3 insertions(+), 123 deletions(-)
>   delete mode 100644 arch/riscv/include/asm/spinlock.h
>   delete mode 100644 arch/riscv/include/asm/spinlock_types.h
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 00fd9c548f26..f8a55d94016d 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -39,6 +39,7 @@ config RISCV
>   	select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
>   	select ARCH_SUPPORTS_HUGETLBFS if MMU
>   	select ARCH_USE_MEMTEST
> +	select ARCH_USE_QUEUED_RWLOCKS
>   	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
>   	select ARCH_WANT_FRAME_POINTERS
>   	select ARCH_WANT_GENERAL_HUGETLB
> diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
> index c3f229ae8033..504f8b7e72d4 100644
> --- a/arch/riscv/include/asm/Kbuild
> +++ b/arch/riscv/include/asm/Kbuild
> @@ -3,6 +3,8 @@ generic-y += early_ioremap.h
>   generic-y += flat.h
>   generic-y += kvm_para.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 += user.h
> diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h
> deleted file mode 100644
> index 88a4d5d0d98a..000000000000
> --- a/arch/riscv/include/asm/spinlock.h
> +++ /dev/null
> @@ -1,99 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0-only */
> -/*
> - * Copyright (C) 2015 Regents of the University of California
> - * Copyright (C) 2017 SiFive
> - */
> -
> -#ifndef _ASM_RISCV_SPINLOCK_H
> -#define _ASM_RISCV_SPINLOCK_H
> -
> -/* This is horible, but the whole file is going away in the next commit. */
> -#define __ASM_GENERIC_QRWLOCK_H
> -
> -#include <linux/kernel.h>
> -#include <asm/current.h>
> -#include <asm/fence.h>
> -#include <asm-generic/spinlock.h>
> -
> -static inline void arch_read_lock(arch_rwlock_t *lock)
> -{
> -	int tmp;
> -
> -	__asm__ __volatile__(
> -		"1:	lr.w	%1, %0\n"
> -		"	bltz	%1, 1b\n"
> -		"	addi	%1, %1, 1\n"
> -		"	sc.w	%1, %1, %0\n"
> -		"	bnez	%1, 1b\n"
> -		RISCV_ACQUIRE_BARRIER
> -		: "+A" (lock->lock), "=&r" (tmp)
> -		:: "memory");
> -}
> -
> -static inline void arch_write_lock(arch_rwlock_t *lock)
> -{
> -	int tmp;
> -
> -	__asm__ __volatile__(
> -		"1:	lr.w	%1, %0\n"
> -		"	bnez	%1, 1b\n"
> -		"	li	%1, -1\n"
> -		"	sc.w	%1, %1, %0\n"
> -		"	bnez	%1, 1b\n"
> -		RISCV_ACQUIRE_BARRIER
> -		: "+A" (lock->lock), "=&r" (tmp)
> -		:: "memory");
> -}
> -
> -static inline int arch_read_trylock(arch_rwlock_t *lock)
> -{
> -	int busy;
> -
> -	__asm__ __volatile__(
> -		"1:	lr.w	%1, %0\n"
> -		"	bltz	%1, 1f\n"
> -		"	addi	%1, %1, 1\n"
> -		"	sc.w	%1, %1, %0\n"
> -		"	bnez	%1, 1b\n"
> -		RISCV_ACQUIRE_BARRIER
> -		"1:\n"
> -		: "+A" (lock->lock), "=&r" (busy)
> -		:: "memory");
> -
> -	return !busy;
> -}
> -
> -static inline int arch_write_trylock(arch_rwlock_t *lock)
> -{
> -	int busy;
> -
> -	__asm__ __volatile__(
> -		"1:	lr.w	%1, %0\n"
> -		"	bnez	%1, 1f\n"
> -		"	li	%1, -1\n"
> -		"	sc.w	%1, %1, %0\n"
> -		"	bnez	%1, 1b\n"
> -		RISCV_ACQUIRE_BARRIER
> -		"1:\n"
> -		: "+A" (lock->lock), "=&r" (busy)
> -		:: "memory");
> -
> -	return !busy;
> -}
> -
> -static inline void arch_read_unlock(arch_rwlock_t *lock)
> -{
> -	__asm__ __volatile__(
> -		RISCV_RELEASE_BARRIER
> -		"	amoadd.w x0, %1, %0\n"
> -		: "+A" (lock->lock)
> -		: "r" (-1)
> -		: "memory");
> -}
> -
> -static inline void arch_write_unlock(arch_rwlock_t *lock)
> -{
> -	smp_store_release(&lock->lock, 0);
> -}
> -
> -#endif /* _ASM_RISCV_SPINLOCK_H */
> diff --git a/arch/riscv/include/asm/spinlock_types.h b/arch/riscv/include/asm/spinlock_types.h
> deleted file mode 100644
> index f2f9b5d7120d..000000000000
> --- a/arch/riscv/include/asm/spinlock_types.h
> +++ /dev/null
> @@ -1,24 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0-only */
> -/*
> - * Copyright (C) 2015 Regents of the University of California
> - */
> -
> -#ifndef _ASM_RISCV_SPINLOCK_TYPES_H
> -#define _ASM_RISCV_SPINLOCK_TYPES_H
> -
> -/* This is horible, but the whole file is going away in the next commit. */
> -#define __ASM_GENERIC_QRWLOCK_TYPES_H
> -
> -#ifndef __LINUX_SPINLOCK_TYPES_RAW_H
> -# error "please don't include this file directly"
> -#endif
> -
> -#include <asm-generic/spinlock_types.h>
> -
> -typedef struct {
> -	volatile unsigned int lock;
> -} arch_rwlock_t;
> -
> -#define __ARCH_RW_LOCK_UNLOCKED		{ 0 }
> -
> -#endif /* _ASM_RISCV_SPINLOCK_TYPES_H */