内核sem、wait_queue_head_t、timer和kernel_thread使用驱动范例-优快云博客

本文介绍了一个基于Linux的定时器驱动实例，详细展示了如何利用sem、wait_queue_head_t等机制实现定时器的功能，并通过kernel_thread启动后台线程进行周期性的操作。

浅析linux内核中sem、wait_queue_head_t、timer和kernel_thread使用驱动范例 # include < linux/ sched. h> # define __TIMER_TEST_MOD1 1 # define __TIMER_TEST_MOD2 2 # define __TIMER_TEST_MOD3 3 # define __TIMER_TEST_MOD4 4 # define __TIMER_TEST_MOD5 5 # define __TIMER_TEST_MOD6 6 # define TIMER_TEST_MOD __TIMER_TEST_MOD6 static inline void restart_timer_delay( struct timer_list * timer, unsigned long msecs) { mod_timer( timer, jiffies + msecs_to_jiffies( msecs) ) ; } struct _sgliethttp_timer { wait_queue_head_t waitQ; struct semaphore sem; struct timer_list timer; int timer_freq; volatile int timer_counts; volatile int thread_run, thread_quited; } ; static struct _sgliethttp_timer sgliethttp_timer, * gliethttp_timer; static void timer_func( unsigned long data) { restart_timer_delay( & gliethttp_timer- > timer, gliethttp_timer- > timer_freq) ; gliethttp_timer- > timer_counts+ + ; # if ( TIMER_TEST_MOD = = __TIMER_TEST_MOD2) up( & gliethttp_timer- > sem) ; # endif # if ( ( TIMER_TEST_MOD = = __TIMER_TEST_MOD3) | | / ( TIMER_TEST_MOD = = __TIMER_TEST_MOD4) | | / ( TIMER_TEST_MOD = = __TIMER_TEST_MOD5) | | / ( TIMER_TEST_MOD = = __TIMER_TEST_MOD6) | | 0/ ) wake_up( & gliethttp_timer- > waitQ) ; //对于wait_event_interruptible_timeout和wait_event_timeout来说, //就是唤醒timer_thread,然后检查pre_timer_count != gliethttp_timer->timer_counts是否为真, //如果为真,那么将退出wait_event_interruptible_timeout和wait_event_timeout. # endif } static int timer_thread( void * data) { # if ( ( TIMER_TEST_MOD = = __TIMER_TEST_MOD1) | | / ( TIMER_TEST_MOD = = __TIMER_TEST_MOD3) | | / ( TIMER_TEST_MOD = = __TIMER_TEST_MOD4) | | 0/ ) int pre_timer_count = gliethttp_timer- > timer_counts; # endif while ( gliethttp_timer- > thread_run) { # if ( TIMER_TEST_MOD = = __TIMER_TEST_MOD1) set_current_state( TASK_INTERRUPTIBLE) ; schedule_timeout( HZ) ; printk( "M" ) ; if ( gliethttp_timer- > timer_counts ! = pre_timer_count) { printk( "L" ) ; pre_timer_count = gliethttp_timer- > timer_counts; } # endif # if ( TIMER_TEST_MOD = = __TIMER_TEST_MOD2) //down_interruptible(&gliethttp_timer->sem); down( & gliethttp_timer- > sem) ; printk( "L" ) ; # endif # if ( TIMER_TEST_MOD = = __TIMER_TEST_MOD3) wait_event_timeout( gliethttp_timer- > waitQ, pre_timer_count ! = gliethttp_timer- > timer_counts, 5* HZ) ; pre_timer_count+ + ; printk( "L" ) ; # endif # if ( TIMER_TEST_MOD = = __TIMER_TEST_MOD4) wait_event_interruptible_timeout( gliethttp_timer- > waitQ, pre_timer_count ! = gliethttp_timer- > timer_counts, 5* HZ) ; pre_timer_count+ + ; printk( "L" ) ; # endif # if ( ( TIMER_TEST_MOD = = __TIMER_TEST_MOD5) | | ( TIMER_TEST_MOD = = __TIMER_TEST_MOD6) ) interruptible_sleep_on_timeout( & gliethttp_timer- > waitQ, 5* HZ) ; printk( "L" ) ; # endif } gliethttp_timer- > thread_quited = 1; return 0; } static int init_gliethttp_timer( void ) { gliethttp_timer = & sgliethttp_timer; init_waitqueue_head( & gliethttp_timer- > waitQ) ; init_MUTEX_LOCKED( & gliethttp_timer- > sem) ; //init_MUTEX(&gliethttp_timer->sem); //sema_init(&gliethttp_timer->sem, 10); gliethttp_timer- > thread_run = 1; gliethttp_timer- > thread_quited = 0; gliethttp_timer- > timer_counts = - 1; gliethttp_timer- > timer_freq = 100; setup_timer( & gliethttp_timer- > timer, timer_func, gliethttp_timer- > timer_freq) ; restart_timer_delay( & gliethttp_timer- > timer, gliethttp_timer- > timer_freq) ; kernel_thread( timer_thread, NULL , 0) ; printk( KERN_DEBUG"timer test start!/n" ) ; printk( KERN_EMERG"timer test start!/n" ) ; printk( KERN_ALERT"timer test start!/n" ) ; printk( KERN_CRIT"timer test start!/n" ) ; printk( KERN_ERR"timer test start!/n" ) ; printk( KERN_WARNING"timer test start!/n" ) ; printk( KERN_NOTICE"timer test start!/n" ) ; printk( KERN_INFO"timer test start!/n" ) ; //没咒念了,只能使用dmesg|tail来查看结果了

return 0; } static void cleanup_gliethttp_timer( void ) { //del_timer(&timer); del_timer_sync( & gliethttp_timer- > timer) ; # if ( TIMER_TEST_MOD = = __TIMER_TEST_MOD6) { gliethttp_timer- > thread_run = 0; wake_up( & gliethttp_timer- > waitQ) ; //如果在等待,那么唤醒timer_thread,让他去检测while(gliethttp_timer->thread_run) while ( gliethttp_timer- > thread_quited = = 0) { set_current_state( TASK_INTERRUPTIBLE) ; schedule_timeout( 1) ; printk( "Q" ) ; } } # endif printk( KERN_DEBUG"/nGoodbye, timer test/n" ) ; } module_init( init_gliethttp_timer) ; module_exit( cleanup_gliethttp_timer)