【Linux设备驱动程序（第三版）】----延迟：超时（schedule_timeout）

【Linux设备驱动程序（第三版）】----延迟：超时（schedule_timeout）

jit.c

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/timer.h>
#include <linux/proc_fs.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <asm/hardirq.h>
#include <linux/sched.h>//jiffies
#include <linux/kernel.h>
#include <linux/types.h>//u64
#include <linux/fs.h>//file_operations, file
#include <linux/completion.h>
#include <asm/uaccess.h>//copy_to_user & copy_from_user

int delay = HZ;

enum jit_files {
JIT_BUSY,
JIT_SCHED,
JIT_QUEUE,
JIT_SCHEDTO
};

int jit_fn(char *buf, char **start, off_t offset, int len, int *eof, void *data)
{
unsigned long j0, j1;
wait_queue_head_t wait;

init_waitqueue_head(&wait);
j0 = jiffies;
j1 = j0 + delay;

switch((long)data){
case JIT_BUSY:
while(time_before(jiffies, j1))
cpu_relax();
break;
case JIT_SCHED:
while(time_before(jiffies, j1))
schedule();
break;
case JIT_QUEUE:
wait_event_interruptible_timeout(wait, 0, delay);
break;
case JIT_SCHEDTO:
set_current_state(TASK_INTERRUPTIBLE);
schedule_timeout(delay);
break;
}
j1 = jiffies;
len = sprintf(buf, "%9li %9li\n", j0, j1);
*start = buf;
return len;
}

int jit_currentime(char *buf, char **start, off_t offset, int len, int *eof, void *data)
{
struct timeval tv1;
struct timespec tv2;
unsigned long j1;
u64 j2;

j1 = jiffies;
j2 = get_jiffies_64();
do_gettimeofday(&tv1);
tv2 = current_kernel_time();

len = 0;
len += sprintf(buf,"0x%08lx 0x%016Lx %10i.%06i\n"
"%40i.%09i\n",
j1, j2,
(int) tv1.tv_sec, (int) tv1.tv_usec,
(int) tv2.tv_sec, (int) tv2.tv_nsec);
*start = buf;
return len;
}

int __init jit_init(void)
{
create_proc_read_entry("jit_currentime", 0, NULL, jit_currentime, NULL);
create_proc_read_entry("jitbusy", 0, NULL, jit_fn, (void *)JIT_BUSY);
create_proc_read_entry("jitsched", 0, NULL, jit_fn, (void *)JIT_SCHED);
create_proc_read_entry("jitqueue", 0, NULL, jit_fn, (void *)JIT_QUEUE);
create_proc_read_entry("jitschedto", 0, NULL, jit_fn, (void *)JIT_SCHEDTO);
return 0;
}

void __exit jit_exit(void)
{
remove_proc_entry("jit_currentime", NULL);
remove_proc_entry("jitbusy", NULL);
remove_proc_entry("jitsched", NULL);
remove_proc_entry("jitqueue", NULL);
remove_proc_entry("jitschedto", NULL);
}

MODULE_LICENSE("Dual BSD/GPL");
module_init(jit_init);
module_exit(jit_exit);

Makefile

obj-m:= jit.o
modules-objs:= jit.o

KDIR:= /usr/src/linux-headers-2.6.31-14-generic/
PWD:= $(shell pwd)

default:
make -C $(KDIR) M=$(PWD) modules
clean:
rm -rf *.ko *.mod.c *.mod.o *.o *.markers *.symvers *.order

装载

insmod jit.ko

测试

dd bs=20 count=5 < /proc/jitschedto

卸载

rmmod jit