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Sun, 04 Apr 2021 22:54:20 -0700 (PDT) MIME-Version: 1.0 References: <1617201040-83905-1-git-send-email-guoren@kernel.org> <1617201040-83905-4-git-send-email-guoren@kernel.org> In-Reply-To: <1617201040-83905-4-git-send-email-guoren@kernel.org> From: Guo Ren Date: Mon, 5 Apr 2021 13:54:08 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v6 3/9] riscv: locks: Introduce ticket-based spinlock implementation To: Guo Ren Cc: linux-riscv , Linux Kernel Mailing List , linux-csky@vger.kernel.org, linux-arch , linuxppc-dev@lists.ozlabs.org, linux-xtensa@linux-xtensa.org, openrisc@lists.librecores.org, sparclinux , Guo Ren , Peter Zijlstra , Anup Patel , Arnd Bergmann X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210405_065424_869999_A24546A1 X-CRM114-Status: GOOD ( 26.99 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Wed, Mar 31, 2021 at 10:32 PM wrote: > > From: Guo Ren > > This patch introduces a ticket lock implementation for riscv, along the > same lines as the implementation for arch/arm & arch/csky. > > We still use qspinlock as default. > > Signed-off-by: Guo Ren > Cc: Peter Zijlstra > Cc: Anup Patel > Cc: Arnd Bergmann > --- > arch/riscv/Kconfig | 7 ++- > arch/riscv/include/asm/spinlock.h | 84 +++++++++++++++++++++++++ > arch/riscv/include/asm/spinlock_types.h | 17 +++++ > 3 files changed, 107 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 67cc65ba1ea1..34d0276f01d5 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -34,7 +34,7 @@ config RISCV > select ARCH_WANT_FRAME_POINTERS > select ARCH_WANT_HUGE_PMD_SHARE if 64BIT > select ARCH_USE_QUEUED_RWLOCKS > - select ARCH_USE_QUEUED_SPINLOCKS > + select ARCH_USE_QUEUED_SPINLOCKS if !RISCV_TICKET_LOCK > select ARCH_USE_QUEUED_SPINLOCKS_XCHG32 > select CLONE_BACKWARDS > select CLINT_TIMER if !MMU > @@ -344,6 +344,11 @@ config NEED_PER_CPU_EMBED_FIRST_CHUNK > def_bool y > depends on NUMA > > +config RISCV_TICKET_LOCK > + bool "Ticket-based spin-locking" > + help > + Say Y here to use ticket-based spin-locking. > + > config RISCV_ISA_C > bool "Emit compressed instructions when building Linux" > default y > diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h > index a557de67a425..90b7eaa950cf 100644 > --- a/arch/riscv/include/asm/spinlock.h > +++ b/arch/riscv/include/asm/spinlock.h > @@ -7,7 +7,91 @@ > #ifndef _ASM_RISCV_SPINLOCK_H > #define _ASM_RISCV_SPINLOCK_H > > +#ifdef CONFIG_RISCV_TICKET_LOCK > +#ifdef CONFIG_32BIT > +#define __ASM_SLLIW "slli\t" > +#define __ASM_SRLIW "srli\t" > +#else > +#define __ASM_SLLIW "slliw\t" > +#define __ASM_SRLIW "srliw\t" > +#endif > + > +/* > + * Ticket-based spin-locking. > + */ > +static inline void arch_spin_lock(arch_spinlock_t *lock) > +{ > + arch_spinlock_t lockval; > + u32 tmp; > + > + asm volatile ( > + "1: lr.w %0, %2 \n" > + " mv %1, %0 \n" > + " addw %0, %0, %3 \n" > + " sc.w %0, %0, %2 \n" > + " bnez %0, 1b \n" > + : "=&r" (tmp), "=&r" (lockval), "+A" (lock->lock) > + : "r" (1 << TICKET_NEXT) > + : "memory"); It's could be optimized by amoadd.w with Anup advice, and I'll update it in the next patchset version: diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h index 90b7eaa950cf..435286ad342b 100644 --- a/arch/riscv/include/asm/spinlock.h +++ b/arch/riscv/include/asm/spinlock.h @@ -22,15 +22,10 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) { arch_spinlock_t lockval; - u32 tmp; asm volatile ( - "1: lr.w %0, %2 \n" - " mv %1, %0 \n" - " addw %0, %0, %3 \n" - " sc.w %0, %0, %2 \n" - " bnez %0, 1b \n" - : "=&r" (tmp), "=&r" (lockval), "+A" (lock->lock) + " amoadd.w %0, %2, %1 \n" + : "=&r" (lockval), "+A" (lock->lock) : "r" (1 << TICKET_NEXT) : "memory"); > + > + smp_cond_load_acquire(&lock->tickets.owner, > + VAL == lockval.tickets.next); > +} > + > +static inline int arch_spin_trylock(arch_spinlock_t *lock) > +{ > + u32 tmp, contended, res; > + > + do { > + asm volatile ( > + " lr.w %0, %3 \n" > + __ASM_SRLIW "%1, %0, %5 \n" > + __ASM_SLLIW "%2, %0, %5 \n" > + " or %1, %2, %1 \n" > + " li %2, 0 \n" > + " sub %1, %1, %0 \n" > + " bnez %1, 1f \n" > + " addw %0, %0, %4 \n" > + " sc.w %2, %0, %3 \n" > + "1: \n" > + : "=&r" (tmp), "=&r" (contended), "=&r" (res), > + "+A" (lock->lock) > + : "r" (1 << TICKET_NEXT), "I" (TICKET_NEXT) > + : "memory"); > + } while (res); > + > + if (!contended) > + __atomic_acquire_fence(); > + > + return !contended; > +} > + > +static inline void arch_spin_unlock(arch_spinlock_t *lock) > +{ > + smp_store_release(&lock->tickets.owner, lock->tickets.owner + 1); > +} > + > +static inline int arch_spin_value_unlocked(arch_spinlock_t lock) > +{ > + return lock.tickets.owner == lock.tickets.next; > +} > + > +static inline int arch_spin_is_locked(arch_spinlock_t *lock) > +{ > + return !arch_spin_value_unlocked(READ_ONCE(*lock)); > +} > + > +static inline int arch_spin_is_contended(arch_spinlock_t *lock) > +{ > + struct __raw_tickets tickets = READ_ONCE(lock->tickets); > + > + return (tickets.next - tickets.owner) > 1; > +} > +#define arch_spin_is_contended arch_spin_is_contended > +#else /* CONFIG_RISCV_TICKET_LOCK */ > #include > +#endif /* CONFIG_RISCV_TICKET_LOCK */ > + > #include > > #endif /* _ASM_RISCV_SPINLOCK_H */ > diff --git a/arch/riscv/include/asm/spinlock_types.h b/arch/riscv/include/asm/spinlock_types.h > index d033a973f287..afbb19841d0f 100644 > --- a/arch/riscv/include/asm/spinlock_types.h > +++ b/arch/riscv/include/asm/spinlock_types.h > @@ -10,7 +10,24 @@ > # error "please don't include this file directly" > #endif > > +#ifdef CONFIG_RISCV_TICKET_LOCK > +#define TICKET_NEXT 16 > + > +typedef struct { > + union { > + u32 lock; > + struct __raw_tickets { > + /* little endian */ > + u16 owner; > + u16 next; > + } tickets; > + }; > +} arch_spinlock_t; > + > +#define __ARCH_SPIN_LOCK_UNLOCKED { { 0 } } > +#else > #include > +#endif > #include > > #endif /* _ASM_RISCV_SPINLOCK_TYPES_H */ > -- > 2.17.1 > -- Best Regards Guo Ren ML: https://lore.kernel.org/linux-csky/ _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv