From: Ralf Baechle Date: Thu, 28 Aug 2008 14:17:49 +0000 (+0100) Subject: MIPS: Rewrite spinlocks to ticket locks. X-Git-Tag: v2.6.28-rc1~719^2~10 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=2a31b03335e570dce5fdd082e0d71d48b2cb4290;p=linux-2.6-omap-h63xx.git MIPS: Rewrite spinlocks to ticket locks. Based on patch by Chad Reese of Cavium Networks. Signed-off-by: Ralf Baechle --- diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index c15416c2e89..16097a8f5c5 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -610,11 +610,6 @@ source "arch/mips/vr41xx/Kconfig" endmenu -config GENERIC_LOCKBREAK - bool - default y - depends on SMP && PREEMPT - config RWSEM_GENERIC_SPINLOCK bool default y diff --git a/arch/mips/include/asm/spinlock.h b/arch/mips/include/asm/spinlock.h index bb897016c49..5d98a3cb85b 100644 --- a/arch/mips/include/asm/spinlock.h +++ b/arch/mips/include/asm/spinlock.h @@ -9,62 +9,125 @@ #ifndef _ASM_SPINLOCK_H #define _ASM_SPINLOCK_H +#include + #include #include /* * Your basic SMP spinlocks, allowing only a single CPU anywhere + * + * Simple spin lock operations. There are two variants, one clears IRQ's + * on the local processor, one does not. + * + * These are fair FIFO ticket locks + * + * (the type definitions are in asm/spinlock_types.h) */ -#define __raw_spin_is_locked(x) ((x)->lock != 0) -#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock) -#define __raw_spin_unlock_wait(x) \ - do { cpu_relax(); } while ((x)->lock) /* - * Simple spin lock operations. There are two variants, one clears IRQ's - * on the local processor, one does not. - * - * We make no fairness assumptions. They have a cost. + * Ticket locks are conceptually two parts, one indicating the current head of + * the queue, and the other indicating the current tail. The lock is acquired + * by atomically noting the tail and incrementing it by one (thus adding + * ourself to the queue and noting our position), then waiting until the head + * becomes equal to the the initial value of the tail. */ +static inline int __raw_spin_is_locked(raw_spinlock_t *lock) +{ + unsigned int counters = ACCESS_ONCE(lock->lock); + + return ((counters >> 14) ^ counters) & 0x1fff; +} + +#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock) +#define __raw_spin_unlock_wait(x) \ + while (__raw_spin_is_locked(x)) { cpu_relax(); } + +static inline int __raw_spin_is_contended(raw_spinlock_t *lock) +{ + unsigned int counters = ACCESS_ONCE(lock->lock); + + return (((counters >> 14) - counters) & 0x1fff) > 1; +} + static inline void __raw_spin_lock(raw_spinlock_t *lock) { - unsigned int tmp; + int my_ticket; + int tmp; if (R10000_LLSC_WAR) { - __asm__ __volatile__( - " .set noreorder # __raw_spin_lock \n" - "1: ll %1, %2 \n" - " bnez %1, 1b \n" - " li %1, 1 \n" - " sc %1, %0 \n" - " beqzl %1, 1b \n" + __asm__ __volatile__ ( + " .set push # __raw_spin_lock \n" + " .set noreorder \n" + " \n" + "1: ll %[ticket], %[ticket_ptr] \n" + " addiu %[my_ticket], %[ticket], 0x4000 \n" + " sc %[my_ticket], %[ticket_ptr] \n" + " beqzl %[my_ticket], 1b \n" " nop \n" - " .set reorder \n" - : "=m" (lock->lock), "=&r" (tmp) - : "m" (lock->lock) - : "memory"); + " srl %[my_ticket], %[ticket], 14 \n" + " andi %[my_ticket], %[my_ticket], 0x1fff \n" + " andi %[ticket], %[ticket], 0x1fff \n" + " bne %[ticket], %[my_ticket], 4f \n" + " subu %[ticket], %[my_ticket], %[ticket] \n" + "2: \n" + " .subsection 2 \n" + "4: andi %[ticket], %[ticket], 0x1fff \n" + "5: sll %[ticket], 5 \n" + " \n" + "6: bnez %[ticket], 6b \n" + " subu %[ticket], 1 \n" + " \n" + " lw %[ticket], %[ticket_ptr] \n" + " andi %[ticket], %[ticket], 0x1fff \n" + " beq %[ticket], %[my_ticket], 2b \n" + " subu %[ticket], %[my_ticket], %[ticket] \n" + " b 5b \n" + " subu %[ticket], %[ticket], 1 \n" + " .previous \n" + " .set pop \n" + : [ticket_ptr] "+m" (lock->lock), + [ticket] "=&r" (tmp), + [my_ticket] "=&r" (my_ticket)); } else { - __asm__ __volatile__( - " .set noreorder # __raw_spin_lock \n" - "1: ll %1, %2 \n" - " bnez %1, 2f \n" - " li %1, 1 \n" - " sc %1, %0 \n" - " beqz %1, 2f \n" + __asm__ __volatile__ ( + " .set push # __raw_spin_lock \n" + " .set noreorder \n" + " \n" + " ll %[ticket], %[ticket_ptr] \n" + "1: addiu %[my_ticket], %[ticket], 0x4000 \n" + " sc %[my_ticket], %[ticket_ptr] \n" + " beqz %[my_ticket], 3f \n" " nop \n" + " srl %[my_ticket], %[ticket], 14 \n" + " andi %[my_ticket], %[my_ticket], 0x1fff \n" + " andi %[ticket], %[ticket], 0x1fff \n" + " bne %[ticket], %[my_ticket], 4f \n" + " subu %[ticket], %[my_ticket], %[ticket] \n" + "2: \n" " .subsection 2 \n" - "2: ll %1, %2 \n" - " bnez %1, 2b \n" - " li %1, 1 \n" - " b 1b \n" - " nop \n" + "3: b 1b \n" + " ll %[ticket], %[ticket_ptr] \n" + " \n" + "4: andi %[ticket], %[ticket], 0x1fff \n" + "5: sll %[ticket], 5 \n" + " \n" + "6: bnez %[ticket], 6b \n" + " subu %[ticket], 1 \n" + " \n" + " lw %[ticket], %[ticket_ptr] \n" + " andi %[ticket], %[ticket], 0x1fff \n" + " beq %[ticket], %[my_ticket], 2b \n" + " subu %[ticket], %[my_ticket], %[ticket] \n" + " b 5b \n" + " subu %[ticket], %[ticket], 1 \n" " .previous \n" - " .set reorder \n" - : "=m" (lock->lock), "=&r" (tmp) - : "m" (lock->lock) - : "memory"); + " .set pop \n" + : [ticket_ptr] "+m" (lock->lock), + [ticket] "=&r" (tmp), + [my_ticket] "=&r" (my_ticket)); } smp_llsc_mb(); @@ -72,55 +135,103 @@ static inline void __raw_spin_lock(raw_spinlock_t *lock) static inline void __raw_spin_unlock(raw_spinlock_t *lock) { - smp_mb(); + int tmp; - __asm__ __volatile__( - " .set noreorder # __raw_spin_unlock \n" - " sw $0, %0 \n" - " .set\treorder \n" - : "=m" (lock->lock) - : "m" (lock->lock) - : "memory"); + smp_llsc_mb(); + + if (R10000_LLSC_WAR) { + __asm__ __volatile__ ( + " # __raw_spin_unlock \n" + "1: ll %[ticket], %[ticket_ptr] \n" + " addiu %[ticket], %[ticket], 1 \n" + " ori %[ticket], %[ticket], 0x2000 \n" + " xori %[ticket], %[ticket], 0x2000 \n" + " sc %[ticket], %[ticket_ptr] \n" + " beqzl %[ticket], 2f \n" + : [ticket_ptr] "+m" (lock->lock), + [ticket] "=&r" (tmp)); + } else { + __asm__ __volatile__ ( + " .set push # __raw_spin_unlock \n" + " .set noreorder \n" + " \n" + " ll %[ticket], %[ticket_ptr] \n" + "1: addiu %[ticket], %[ticket], 1 \n" + " ori %[ticket], %[ticket], 0x2000 \n" + " xori %[ticket], %[ticket], 0x2000 \n" + " sc %[ticket], %[ticket_ptr] \n" + " beqz %[ticket], 2f \n" + " nop \n" + " \n" + " .subsection 2 \n" + "2: b 1b \n" + " ll %[ticket], %[ticket_ptr] \n" + " .previous \n" + " .set pop \n" + : [ticket_ptr] "+m" (lock->lock), + [ticket] "=&r" (tmp)); + } } static inline unsigned int __raw_spin_trylock(raw_spinlock_t *lock) { - unsigned int temp, res; + int tmp, tmp2, tmp3; if (R10000_LLSC_WAR) { - __asm__ __volatile__( - " .set noreorder # __raw_spin_trylock \n" - "1: ll %0, %3 \n" - " ori %2, %0, 1 \n" - " sc %2, %1 \n" - " beqzl %2, 1b \n" - " nop \n" - " andi %2, %0, 1 \n" - " .set reorder" - : "=&r" (temp), "=m" (lock->lock), "=&r" (res) - : "m" (lock->lock) - : "memory"); + __asm__ __volatile__ ( + " .set push # __raw_spin_trylock \n" + " .set noreorder \n" + " \n" + "1: ll %[ticket], %[ticket_ptr] \n" + " srl %[my_ticket], %[ticket], 14 \n" + " andi %[my_ticket], %[my_ticket], 0x1fff \n" + " andi %[now_serving], %[ticket], 0x1fff \n" + " bne %[my_ticket], %[now_serving], 3f \n" + " addiu %[ticket], %[ticket], 0x4000 \n" + " sc %[ticket], %[ticket_ptr] \n" + " beqzl %[ticket], 1b \n" + " li %[ticket], 1 \n" + "2: \n" + " .subsection 2 \n" + "3: b 2b \n" + " li %[ticket], 0 \n" + " .previous \n" + " .set pop \n" + : [ticket_ptr] "+m" (lock->lock), + [ticket] "=&r" (tmp), + [my_ticket] "=&r" (tmp2), + [now_serving] "=&r" (tmp3)); } else { - __asm__ __volatile__( - " .set noreorder # __raw_spin_trylock \n" - "1: ll %0, %3 \n" - " ori %2, %0, 1 \n" - " sc %2, %1 \n" - " beqz %2, 2f \n" - " andi %2, %0, 1 \n" + __asm__ __volatile__ ( + " .set push # __raw_spin_trylock \n" + " .set noreorder \n" + " \n" + " ll %[ticket], %[ticket_ptr] \n" + "1: srl %[my_ticket], %[ticket], 14 \n" + " andi %[my_ticket], %[my_ticket], 0x1fff \n" + " andi %[now_serving], %[ticket], 0x1fff \n" + " bne %[my_ticket], %[now_serving], 3f \n" + " addiu %[ticket], %[ticket], 0x4000 \n" + " sc %[ticket], %[ticket_ptr] \n" + " beqz %[ticket], 4f \n" + " li %[ticket], 1 \n" + "2: \n" " .subsection 2 \n" - "2: b 1b \n" - " nop \n" + "3: b 2b \n" + " li %[ticket], 0 \n" + "4: b 1b \n" + " ll %[ticket], %[ticket_ptr] \n" " .previous \n" - " .set reorder" - : "=&r" (temp), "=m" (lock->lock), "=&r" (res) - : "m" (lock->lock) - : "memory"); + " .set pop \n" + : [ticket_ptr] "+m" (lock->lock), + [ticket] "=&r" (tmp), + [my_ticket] "=&r" (tmp2), + [now_serving] "=&r" (tmp3)); } smp_llsc_mb(); - return res == 0; + return tmp; } /* diff --git a/arch/mips/include/asm/spinlock_types.h b/arch/mips/include/asm/spinlock_types.h index ce26c5048b1..adeedaa116c 100644 --- a/arch/mips/include/asm/spinlock_types.h +++ b/arch/mips/include/asm/spinlock_types.h @@ -6,7 +6,12 @@ #endif typedef struct { - volatile unsigned int lock; + /* + * bits 0..13: serving_now + * bits 14 : junk data + * bits 15..28: ticket + */ + unsigned int lock; } raw_spinlock_t; #define __RAW_SPIN_LOCK_UNLOCKED { 0 }