Messages in this thread | | | Subject | Re: [patch] 2.4.4 alpha semaphores optimization | Date | Fri, 04 May 2001 10:22:53 +0100 | From | David Howells <> |
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Hello Ivan,
One reason I picked "signed long" as the count type in the lib/rwsem.c is that this would be 64 bits on a 64-bit arch such as the alpha.
So I've taken your idea for include/asm-alpha/rwsem.h and modified it a little. You'll find it attached at the bottom.
I don't know whether it will (a) compile, or (b) work... I don't have an alpha to play with.
I also don't know the alpha function calling convention, so I can't put direct calls to the fallback routines in lib/rwsem.c from the ".subsection 2" bits. Can you do that, or can you tell me how the calling convention works?
Cheers, David
=============================================================================== #ifndef _ALPHA_RWSEM_H #define _ALPHA_RWSEM_H
/* * Written by Ivan Kokshaysky <ink@jurassic.park.msu.ru>, 2001. * Based on asm-alpha/semaphore.h and asm-i386/rwsem.h */
#ifndef _LINUX_RWSEM_H #error please dont include asm/rwsem.h directly, use linux/rwsem.h instead #endif
#ifdef __KERNEL__
#include <linux/list.h> #include <linux/spinlock.h>
struct rwsem_waiter;
extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);
/* * the semaphore definition */ struct rw_semaphore { signed long count; #define RWSEM_UNLOCKED_VALUE 0x0000000000000000 #define RWSEM_ACTIVE_BIAS 0x0000000000000001 #define RWSEM_ACTIVE_MASK 0x00000000ffffffff #define RWSEM_WAITING_BIAS (-0x0000000100000000) #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) spinlock_t wait_lock; struct list_head wait_list; #if RWSEM_DEBUG int debug; #endif };
#if RWSEM_DEBUG #define __RWSEM_DEBUG_INIT , 0 #else #define __RWSEM_DEBUG_INIT /* */ #endif
#define __RWSEM_INITIALIZER(name) \ { ATOMIC_INIT(RWSEM_UNLOCKED_VALUE), SPIN_LOCK_UNLOCKED, \ LIST_HEAD_INIT((name).wait_list) __RWSEM_DEBUG_INIT }
#define DECLARE_RWSEM(name) \ struct rw_semaphore name = __RWSEM_INITIALIZER(name)
static inline void init_rwsem(struct rw_semaphore *sem) { sem->count = RWSEM_UNLOCKED_VALUE; spin_lock_init(&sem->wait_lock); INIT_LIST_HEAD(&sem->wait_list); #if RWSEM_DEBUG sem->debug = 0; #endif }
static inline void __down_read(struct rw_semaphore *sem) { signed long oldcount, temp; __asm__ __volatile__( "1: ldq_l %0,%1\n" " addq %0,%3,%2\n" " stq_c %2,%1\n" " beq %2,2f\n" #ifdef CONFIG_SMP " mb\n" #endif ".subsection 2\n" "2: br 1b\n" ".previous" :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp) :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
if (oldcount < 0) rwsem_down_read_failed(sem); }
static inline void __down_write(struct rw_semaphore *sem) { signed long granted, temp; __asm__ __volatile__( "1: ldq_l %0,%1\n" " addq %0,%3,%2\n" " stq_c %2,%1\n" " beq %2,2f\n" #ifdef CONFIG_SMP " mb\n" " cmpeq %0,0,%0\n" #endif ".subsection 2\n" "2: br 1b\n" ".previous" :"=&r" (granted), "=m" (sem->count), "=&r" (temp) :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
if (!granted) rwsem_down_write_failed(sem); }
static inline void __up_read(struct rw_semaphore *sem) { signed long oldcount, temp; __asm__ __volatile__( "1: ldq_l %0,%1\n" " subq %0,%3,%2\n" " stq_c %2,%1\n" " beq %2,2f\n" #ifdef CONFIG_SMP " mb\n" #endif ".subsection 2\n" "2: br 1b\n" ".previous" :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp) :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
if (oldcount < 0) if ((count & RWSEM_ACTIVE_MASK) == 0) rwsem_wake(sem); }
static inline void __up_write(struct rw_semaphore *sem) { signed long count, cmp; __asm__ __volatile__( "1: ldq_l %0,%1\n" " subq %0,%3,%2\n" " stq_c %2,%1\n" " beq %2,2f\n" #ifdef CONFIG_SMP " mb\n" " cmpeq %0,%3,%2\n" " subq %0,%3,%0\n" #endif ".subsection 2\n" "2: br 1b\n" ".previous" :"=&r" (count), "=m" (sem->count), "=&r" (cmp) :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
if (!cmp) if ((count & RWSEM_ACTIVE_MASK) == 0) rwsem_wake(sem); }
#define rwsem_atomic_add(val, sem) atomic_add(val, &(sem)->count) #define rwsem_atomic_update(val, sem) atomic_add_return(val, &(sem)->count)
#endif /* __KERNEL__ */ #endif /* _ALPHA_RWSEM_H */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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