Linux内核API seqlock_init

seqlock_init():初始化顺序锁x,同时对顺序锁的顺序号进行初始化。

seqlock_init文件包含

#include <linux/seqlock.h>

seqlock_init宏定义:

在内核源码中的位置:linux-3.19.3/include/linux/seqlock.h

宏定义格式:

#define seqlock_init(x)                          \
    do {                                         \
        seqcount_init(&(x)->seqcount);           \
        spin_lock_init(&(x)->lock);              \
    } while (0)

seqlock_init输入参数说明

  • seqlock_init()的参数x表示指向顺序锁结构体的指针。顺序锁结构体seqlock_t在内核文件linux-3.19.3/include/linux/seqlock.h中定义:
typedef struct {
    struct seqcount seqcount;
    spinlock_t lock;
} seqlock_t;

结构体中包括以下两个字段:

  • seqcount:用来记录申请顺序锁的顺序号,定义见linux-3.19.3/include/linux/seqlock.h,格式如下:
typedef struct seqcount {
    unsigned sequence;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
    struct lockdep_map dep_map;
#endif
} seqcount_t;
  • lock:自旋锁结构体。

顺序锁是对自旋锁的一种优化,对于顺序锁,读者不会被写者阻塞,也即是说,读者可以在写者对被顺序锁保护的共享资源进行写操作时继续读操作,而不必自旋在那里等待写者完成写操作,写者也不必等待所有读者完成读操作后再执行写操作。但是,写者与写者之间仍然是互斥的,即如果有写者在进行写操作,其他写者必须自旋在那里,直到该写者释放了顺序锁。

seqlock_init返回参数说明

  • 该宏无返回值。

seqlock_init实例解析

编写测试文件:seqlock_init.c

头文件及全局变量声明如下:

#include <linux/seqlock.h>
#include <linux/init.h>
#include <linux/module.h>
MODULE_LICENSE("GPL");
static int __init seqlock_init_init(void);
static void __exit seqlock_init_exit(void);

seqlock_t seqlock ;

模块初始化函数:

int __init seqlock_init_init(void)
{
    seqlock_init( &seqlock );       //初始化顺序锁
    printk("after seqlock_init, sequence: %d\n\n", seqlock.seqcount.sequence);

    write_seqlock( &seqlock );      //写者第一次申请顺序锁
    printk("first write_seqlock, sequence: %d\n\n", seqlock.seqcount.sequence);

    write_sequnlock( &seqlock );    //写者第一次释放顺序锁
    printk("first write_sequnlock, sequence: %d\n\n", seqlock.seqcount.sequence);

    write_seqlock( &seqlock );      //写者第二次申请顺序锁
    printk("second write_seqlock, sequence: %d\n\n", seqlock.seqcount.sequence);

    write_sequnlock( &seqlock );    //写者第二次申请顺序锁
    printk("second write_sequnlock, sequence: %d\n\n", seqlock.seqcount.sequence);
    return 0;
}

模块退出函数:

void __exit seqlock_init_exit(void)
{
    printk("exit! \n");
}

模块初始化及退出函数调用:

module_init(seqlock_init_init);
module_exit(seqlock_init_exit);

实例运行结果及分析:

首先编译模块,执行命令insmod seqlock_init.ko插入模块,然后执行命令dmesg -c,会出现如图所示的结果。

Linux内核API seqlock_init

结果分析:

测试程序中调用了函数write_seqlock()和write_sequnlock(),其功能参考极客笔记关于它们的分析。

宏seqlock_init()以及函数write_seqlock()、write_sequnlock()的功能分别与宏spin_lock_init()、spin_lock()、spin_unlock()的功能相似,只是增加了对结构体seqlock_t中顺序号sequence的操作。顺序锁通过seqlock_init()初始化后,sequence也被初始化为0,以后的每次申请或释放锁操作,sequence都会在原有数值上执行加1操作。

赞(0)
未经允许不得转载:极客笔记 » Linux内核API seqlock_init

评论 抢沙发

  • 昵称 (必填)
  • 邮箱 (必填)
  • 网址
Linux内核API 模块机制
Linux内核API 模块机制Linux内核API __module_addressLinux内核API __module_text_addressLinux内核API __print_symbolLinux内核API __symbol_getLinux内核API __symbol_putLinux内核API find_moduleLinux内核API find_symbolLinux内核API module_is_liveLinux内核API module_putLinux内核API module_refcountLinux内核API sprint_symbolLinux内核API symbol_put_addrLinux内核API try_module_get
Linux内核API 进程管理
Linux内核API 进程管理Linux内核API __task_pid_nr_nsLinux内核API find_get_pidLinux内核API find_pid_nsLinux内核API find_vpidLinux内核API get_pidLinux内核API get_task_mmLinux内核API mmputLinux内核API ns_of_pidLinux内核API pid_nrLinux内核API pid_taskLinux内核API pid_vnrLinux内核API put_pidLinux内核API task_active_pid_nsLinux内核API task_tgid_nr_ns
Linux内核API 进程调度
Linux内核API 进程调度Linux内核API __wake_upLinux内核API __wake_up_syncLinux内核API __wake_up_sync_keyLinux内核API abort_exclusive_waitLinux内核API add_wait_queueLinux内核API add_wait_queue_exclusiveLinux内核API autoremove_wake_functionLinux内核API completeLinux内核API complete_allLinux内核API completion_doneLinux内核API current_thread_infoLinux内核API default_wake_functionLinux内核API do_exitLinux内核API finish_waitLinux内核API init_waitqueue_entryLinux内核API init_waitqueue_headLinux内核API kthread_create_on_nodeLinux内核API kthread_stopLinux内核API prepare_to_waitLinux内核API prepare_to_wait_exclusiveLinux内核API remove_wait_queueLinux内核API sched_setschedulerLinux内核API set_cpus_allowed_ptrLinux内核API set_user_niceLinux内核API task_niceLinux内核API try_wait_for_completionLinux内核API wait_for_completionLinux内核API wait_for_completion_interruptible_timeoutLinux内核API wait_for_completion_killableLinux内核API wait_for_completion_timeoutLinux内核API wake_up_processLinux内核API yield
Linux内核API 中断机制
Linux内核API 中断机制Linux内核API __tasklet_hi_scheduleLinux内核API __tasklet_scheduleLinux内核API disable_irqLinux内核API disable_irq_nosyncLinux内核API disable_irq_wakeLinux内核API enable_irqLinux内核API enable_irq_wakeLinux内核API free_irqLinux内核API irq_set_chipLinux内核API irq_set_chip_dataLinux内核API irq_set_irq_typeLinux内核API irq_set_irq_wakeLinux内核API remove_irqLinux内核API request_irqLinux内核API request_threaded_irqLinux内核API setup_irqLinux内核API tasklet_disableLinux内核API tasklet_disable_nosyncLinux内核API tasklet_enableLinux内核API tasklet_hi_scheduleLinux内核API tasklet_initLinux内核API tasklet_killLinux内核API tasklet_scheduleLinux内核API tasklet_trylockLinux内核API tasklet_unlock
Linux内核API 内存管理
Linux内核API 内存管理Linux内核API __free_pagesLinux内核API __get_free_pagesLinux内核API __get_vm_areaLinux内核API __kreallocLinux内核API alloc_pagesLinux内核API alloc_pages_exactLinux内核API find_vmaLinux内核API find_vma_intersectionLinux内核API free_pagesLinux内核API free_pages_exactLinux内核API get_unmapped_areaLinux内核API get_zeroed_pageLinux内核API kcallocLinux内核API kfreeLinux内核API kmallocLinux内核API kmem_cache_allocLinux内核API kmem_cache_createLinux内核API kmem_cache_destroyLinux内核API kmem_cache_freeLinux内核API kmem_cache_zallocLinux内核API kmemdupLinux内核API ksizeLinux内核API kstrdupLinux内核API kstrndupLinux内核API kzallocLinux内核API memdup_userLinux内核API mempool_allocLinux内核API mempool_alloc_pagesLinux内核API mempool_alloc_slabLinux内核API mempool_createLinux内核API mempool_destroyLinux内核API mempool_freeLinux内核API mempool_free_pagesLinux内核API mempool_free_slabLinux内核API mempool_kfreeLinux内核API mempool_kmallocLinux内核API mempool_resizeLinux内核API nr_free_buffer_pagesLinux内核API page_addressLinux内核API page_cache_getLinux内核API page_cache_releaseLinux内核API page_zoneLinux内核API probe_kernel_addressLinux内核API probe_kernel_readLinux内核API vfreeLinux内核API vma_pagesLinux内核API vmallocLinux内核API vmalloc_to_pageLinux内核API vmalloc_to_pfnLinux内核API vmalloc_user
Linux内核API 定时机制
Linux内核API 定时机制Linux内核API __round_jiffiesLinux内核API __round_jiffies_relativeLinux内核API __round_jiffies_upLinux内核API __round_jiffies_up_relativeLinux内核API add_timerLinux内核API current_kernel_timeLinux内核API del_timerLinux内核API del_timer_syncLinux内核API do_gettimeofdayLinux内核API do_settimeofdayLinux内核API get_secondsLinux内核API getnstimeofdayLinux内核API init_timerLinux内核API init_timer_deferrableLinux内核API init_timer_keyLinux内核API init_timer_on_stackLinux内核API init_timer_on_stack_keyLinux内核API mktimeLinux内核API mod_timerLinux内核API mod_timer_pendingLinux内核API ns_to_timespecLinux内核API ns_to_timevalLinux内核API round_jiffiesLinux内核API round_jiffies_relativeLinux内核API round_jiffies_upLinux内核API round_jiffies_up_relativeLinux内核API set_normalized_timespecLinux内核API setup_timerLinux内核API setup_timer_on_stackLinux内核API timer_pendingLinux内核API timespec_add_nsLinux内核API timespec_compareLinux内核API timespec_equalLinux内核API timespec_subLinux内核API timespec_to_nsLinux内核API timeval_compareLinux内核API timeval_to_nsLinux内核API try_to_del_timer_sync
Linux内核API 同步机制
Linux内核API 同步机制Linux内核API atomic_addLinux内核API atomic_add_negativeLinux内核API atomic_add_returnLinux内核API atomic_add_unlessLinux内核API atomic_cmpxchgLinux内核API atomic_decLinux内核API atomic_dec_and_testLinux内核API atomic_incLinux内核API atomic_inc_and_testLinux内核API atomic_readLinux内核API atomic_setLinux内核API atomic_subLinux内核API atomic_sub_and_testLinux内核API atomic_sub_returnLinux内核API downLinux内核API down_interruptibleLinux内核API down_killableLinux内核API down_readLinux内核API down_read_trylockLinux内核API down_timeoutLinux内核API down_trylockLinux内核API down_writeLinux内核API down_write_trylockLinux内核API downgrade_writeLinux内核API init_rwsemLinux内核API read_seqbeginLinux内核API read_seqretryLinux内核API sema_initLinux内核API seqlock_initLinux内核API upLinux内核API up_readLinux内核API up_writeLinux内核API write_seqlockLinux内核API write_sequnlock
Linux内核API 文件系统
Linux内核API 文件系统Linux内核API __mnt_is_readonlyLinux内核API current_umaskLinux内核API d_allocLinux内核API d_find_aliasLinux内核API dputLinux内核API fgetLinux内核API generic_fillattrLinux内核API get_fs_typeLinux内核API get_max_filesLinux内核API get_superLinux内核API have_submountsLinux内核API I_BDEVLinux内核API inode_add_bytesLinux内核API inode_get_bytesLinux内核API inode_set_bytesLinux内核API inode_sub_bytesLinux内核API is_bad_inodeLinux内核API make_bad_inodeLinux内核API may_umountLinux内核API may_umount_treeLinux内核API mnt_want_writeLinux内核API notify_changeLinux内核API put_unused_fdLinux内核API unshare_fs_structLinux内核API vfs_fstatLinux内核API vfs_getattrLinux内核API vfs_statfs
Linux内核API 设备管理
Linux内核API 设备管理Linux内核API __class_createLinux内核API __class_registerLinux内核API cdev_addLinux内核API cdev_allocLinux内核API cdev_delLinux内核API cdev_initLinux内核API class_createLinux内核API class_destroyLinux内核API class_registerLinux内核API class_unregisterLinux内核API device_addLinux内核API device_createLinux内核API device_delLinux内核API device_destroyLinux内核API device_initializeLinux内核API device_registerLinux内核API device_renameLinux内核API device_unregisterLinux内核API get_deviceLinux内核API put_deviceLinux内核API register_chrdevLinux内核API unregister_chrdev