From: Peter Zijlstra <peterz@infradead.org>
To: Guo Ren <ren_guo@c-sky.com>
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
tglx@linutronix.de, daniel.lezcano@linaro.org,
jason@lakedaemon.net, arnd@arndb.de, devicetree@vger.kernel.org,
andrea.parri@amarulasolutions.com, c-sky_gcc_upstream@c-sky.com,
gnu-csky@mentor.com, thomas.petazzoni@bootlin.com,
wbx@uclibc-ng.org, green.hu@gmail.com
Subject: Re: [PATCH V3 11/27] csky: Atomic operations
Date: Wed, 12 Sep 2018 17:55:14 +0200 [thread overview]
Message-ID: <20180912155514.GV24082@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <93e8b592e429c156ad4d4ca5d85ef48fd0ab8b70.1536757532.git.ren_guo@c-sky.com>
On Wed, Sep 12, 2018 at 09:24:45PM +0800, Guo Ren wrote:
> +#define ATOMIC_OP(op, c_op) \
> +static inline void atomic_##op(int i, atomic_t *v) \
> +{ \
> + unsigned long tmp; \
> + \
> + smp_mb(); \
> + asm volatile ( \
> + "1: ldex.w %0, (%2) \n" \
> + " " #op " %0, %1 \n" \
> + " stex.w %0, (%2) \n" \
> + " bez %0, 1b \n" \
> + : "=&r" (tmp) \
> + : "r" (i), "r"(&v->counter) \
> + : "memory"); \
> + smp_mb(); \
> +}
ATOMIC_OP doesn't need to imply any smp_mb()'s what so ever.
> +#define ATOMIC_OP_RETURN(op, c_op) \
> +static inline int atomic_##op##_return(int i, atomic_t *v) \
> +{ \
> + unsigned long tmp, ret; \
> + \
> + smp_mb(); \
> + asm volatile ( \
> + "1: ldex.w %0, (%3) \n" \
> + " " #op " %0, %2 \n" \
> + " mov %1, %0 \n" \
> + " stex.w %0, (%3) \n" \
> + " bez %0, 1b \n" \
> + : "=&r" (tmp), "=&r" (ret) \
> + : "r" (i), "r"(&v->counter) \
> + : "memory"); \
> + smp_mb(); \
> + \
> + return ret; \
> +}
> +
> +#define ATOMIC_FETCH_OP(op, c_op) \
> +static inline int atomic_fetch_##op(int i, atomic_t *v) \
> +{ \
> + unsigned long tmp, ret; \
> + \
> + smp_mb(); \
> + asm volatile ( \
> + "1: ldex.w %0, (%3) \n" \
> + " mov %1, %0 \n" \
> + " " #op " %0, %2 \n" \
> + " stex.w %0, (%3) \n" \
> + " bez %0, 1b \n" \
> + : "=&r" (tmp), "=&r" (ret) \
> + : "r" (i), "r"(&v->counter) \
> + : "memory"); \
> + smp_mb(); \
> + \
> + return ret; \
> +}
For these you could generate _relaxed variants and not provide smp_mb()
inside them.
> +#else /* CONFIG_CPU_HAS_LDSTEX */
> +
> +#include <linux/irqflags.h>
> +
> +#define ATOMIC_OP(op, c_op) \
> +static inline void atomic_##op(int i, atomic_t *v) \
> +{ \
> + unsigned long tmp, flags; \
> + \
> + raw_local_irq_save(flags); \
> + \
> + asm volatile ( \
> + " ldw %0, (%2) \n" \
> + " " #op " %0, %1 \n" \
> + " stw %0, (%2) \n" \
> + : "=&r" (tmp) \
> + : "r" (i), "r"(&v->counter) \
> + : "memory"); \
> + \
> + raw_local_irq_restore(flags); \
> +}
Is this really 'better' than the generic UP fallback implementation?
> diff --git a/arch/csky/include/asm/spinlock.h b/arch/csky/include/asm/spinlock.h
> new file mode 100644
> index 0000000..f1081bb
> --- /dev/null
> +++ b/arch/csky/include/asm/spinlock.h
> @@ -0,0 +1,286 @@
> +#ifndef __ASM_CSKY_SPINLOCK_H
> +#define __ASM_CSKY_SPINLOCK_H
> +
> +#include <linux/spinlock_types.h>
> +#include <asm/barrier.h>
> +
> +#ifdef CONFIG_QUEUED_RWLOCKS
> +
> +/*
> + * Ticket-based spin-locking.
> + */
> +static inline void arch_spin_lock(arch_spinlock_t *lock)
> +{
> + arch_spinlock_t lockval;
> + u32 ticket_next = 1 << TICKET_NEXT;
> + u32 *p = &lock->lock;
> + u32 tmp;
> +
> + smp_mb();
spin_lock() doesn't need smp_mb() before.
> + asm volatile (
> + "1: ldex.w %0, (%2) \n"
> + " mov %1, %0 \n"
> + " add %0, %3 \n"
> + " stex.w %0, (%2) \n"
> + " bez %0, 1b \n"
> + : "=&r" (tmp), "=&r" (lockval)
> + : "r"(p), "r"(ticket_next)
> + : "cc");
> +
> + while (lockval.tickets.next != lockval.tickets.owner) {
> + lockval.tickets.owner = READ_ONCE(lock->tickets.owner);
> + }
> +
> + smp_mb();
> +}
> +
> +static inline int arch_spin_trylock(arch_spinlock_t *lock)
> +{
> + u32 tmp, contended, res;
> + u32 ticket_next = 1 << TICKET_NEXT;
> + u32 *p = &lock->lock;
> +
> + smp_mb();
idem.
> + do {
> + asm volatile (
> + " ldex.w %0, (%3) \n"
> + " movi %2, 1 \n"
> + " rotli %1, %0, 16 \n"
> + " cmpne %1, %0 \n"
> + " bt 1f \n"
> + " movi %2, 0 \n"
> + " add %0, %0, %4 \n"
> + " stex.w %0, (%3) \n"
> + "1: \n"
> + : "=&r" (res), "=&r" (tmp), "=&r" (contended)
> + : "r"(p), "r"(ticket_next)
> + : "cc");
> + } while (!res);
> +
> + if (!contended)
> + smp_mb();
> +
> + return !contended;
> +}
> +
> +static inline void arch_spin_unlock(arch_spinlock_t *lock)
> +{
> + smp_mb();
> + lock->tickets.owner++;
> + smp_mb();
spin_unlock() doesn't need smp_mb() after.
> +}
> +
> +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
> +
> +#include <asm/qrwlock.h>
> +
> +/* See include/linux/spinlock.h */
> +#define smp_mb__after_spinlock() smp_mb()
> +
> +#else /* CONFIG_QUEUED_RWLOCKS */
> +
> +/*
> + * Test-and-set spin-locking.
> + */
Why retain that?
same comments; it has far too many smp_mb()s in.
> +#endif /* CONFIG_QUEUED_RWLOCKS */
> +#endif /* __ASM_CSKY_SPINLOCK_H */
> diff --git a/arch/csky/include/asm/spinlock_types.h b/arch/csky/include/asm/spinlock_types.h
> new file mode 100644
> index 0000000..7e825c2
> --- /dev/null
> +++ b/arch/csky/include/asm/spinlock_types.h
> @@ -0,0 +1,35 @@
> +#ifndef __ASM_CSKY_SPINLOCK_TYPES_H
> +#define __ASM_CSKY_SPINLOCK_TYPES_H
> +
> +#ifndef __LINUX_SPINLOCK_TYPES_H
> +# error "please don't include this file directly"
> +#endif
> +
> +#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 } }
> +
> +#ifdef CONFIG_QUEUED_RWLOCKS
> +#include <asm-generic/qrwlock_types.h>
> +
> +#else /* CONFIG_NR_CPUS > 2 */
> +
> +typedef struct {
> + u32 lock;
> +} arch_rwlock_t;
> +
> +#define __ARCH_RW_LOCK_UNLOCKED { 0 }
> +
> +#endif /* CONFIG_QUEUED_RWLOCKS */
> +#endif /* __ASM_CSKY_SPINLOCK_TYPES_H */
next prev parent reply other threads:[~2018-09-12 15:55 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-12 13:24 [PATCH V4 00/27] C-SKY(csky) Linux Kernel Port Guo Ren
2018-09-12 13:24 ` [PATCH V3 01/27] csky: Build infrastructure Guo Ren
2018-09-12 13:24 ` [PATCH V3 02/27] csky: defconfig Guo Ren
2018-09-12 13:24 ` [PATCH V3 03/27] csky: Kernel booting Guo Ren
2018-09-12 13:24 ` [PATCH V3 04/27] csky: Exception handling Guo Ren
2018-09-12 13:24 ` [PATCH V3 05/27] csky: System Call Guo Ren
2018-09-12 13:24 ` [PATCH V3 06/27] csky: Cache and TLB routines Guo Ren
2018-09-12 13:24 ` [PATCH V3 07/27] csky: MMU and page table management Guo Ren
2018-09-12 13:24 ` [PATCH V3 08/27] csky: Process management and Signal Guo Ren
2018-09-12 13:24 ` [PATCH V3 09/27] csky: VDSO and rt_sigreturn Guo Ren
2018-09-12 13:24 ` [PATCH V3 10/27] csky: IRQ handling Guo Ren
2018-09-12 13:24 ` [PATCH V3 12/27] csky: ELF and module probe Guo Ren
2018-09-12 13:24 ` [PATCH V3 13/27] csky: Library functions Guo Ren
2018-09-12 13:24 ` [PATCH V3 14/27] csky: User access Guo Ren
2018-09-12 13:24 ` [PATCH V3 15/27] csky: Debug and Ptrace GDB Guo Ren
2018-09-12 13:24 ` [PATCH V3 16/27] csky: SMP support Guo Ren
2018-09-12 13:24 ` [PATCH V3 18/27] dt-bindings: csky CPU Bindings Guo Ren
2018-09-12 13:24 ` [PATCH V3 19/27] dt-bindings: timer: gx6605s SOC timer Guo Ren
2018-09-12 13:24 ` [PATCH V3 20/27] dt-bindings: timer: C-SKY Multi-processor timer Guo Ren
2018-09-12 13:24 ` [PATCH V3 22/27] dt-bindings: interrupt-controller: C-SKY SMP intc Guo Ren
2018-09-12 13:24 ` [PATCH V3 23/27] clocksource: add gx6605s SOC system timer Guo Ren
[not found] ` <abb46d366b513b814f7af234d560306a818b7324.1536757532.git.ren_guo@c-sky.com>
2018-09-12 14:22 ` [PATCH V3 17/27] csky: Misc headers Arnd Bergmann
2018-09-12 14:30 ` [PATCH V4 00/27] C-SKY(csky) Linux Kernel Port Arnd Bergmann
2018-09-14 14:37 ` Guo Ren
2018-09-14 14:46 ` Arnd Bergmann
2018-09-14 16:02 ` Guo Ren
2018-09-14 16:09 ` Arnd Bergmann
2018-09-14 23:28 ` Guo Ren
2018-09-20 17:52 ` Palmer Dabbelt
2018-09-21 5:18 ` Arnd Bergmann
2018-09-21 23:48 ` Guo Ren
2018-09-24 7:21 ` Geert Uytterhoeven
2018-09-24 8:47 ` Arnd Bergmann
2018-09-16 1:07 ` Guo Ren
2018-09-16 4:53 ` Guo Ren
2018-09-17 11:54 ` Stephen Rothwell
2018-09-17 12:03 ` Stephen Rothwell
2018-09-17 14:50 ` Guo Ren
2018-09-17 14:37 ` Guo Ren
[not found] ` <93e8b592e429c156ad4d4ca5d85ef48fd0ab8b70.1536757532.git.ren_guo@c-sky.com>
2018-09-12 15:55 ` Peter Zijlstra [this message]
2018-09-15 14:55 ` [PATCH V3 11/27] csky: Atomic operations Guo Ren
2018-09-17 8:17 ` Peter Zijlstra
2018-09-17 15:05 ` Guo Ren
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