尝试用spin_lock_irqsave(),发现没有禁掉时钟中断,不知道我哪里理解错了?
kernel版本:
- uname -a 结果:
- Linux localhost.localdomain 2.6.18 #1 Sat Jul 19 13:06:00 EDT 2008 i686 i686 i386 GNU/Linux
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我的代码:
- #include <linux/kernel.h>
- #include <linux/init.h>
- #include <linux/module.h>
- #include <linux/spinlock.h>
- static spinlock_t my_spinlock;
- static int __init init_test()
- {
- unsigned long flags;
- spin_lock_init(&my_spinlock);
- spin_lock_irqsave(&my_spinlock, flags);
- return 0;
- }
- static void __exit init_exit()
- {
- return;
- }
- module_init(init_test);
- module_exit(init_exit);
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加载module以后,通过这样的命令查看墙上时钟:
- #date; sleep 2; date
- 输出结果:
- Sun Apr 19 12:59:42 EDT 2009
- Sun Apr 19 12:59:44 EDT 2009
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墙上时钟仍然在变化,说明时钟中断没有被禁掉。
但我理解的spin_lock_irqsave()会通过cli关掉所有IRQ,并且我在module中也没有spin_unlock_irqrestore(),所以按理说在加载了这个module之后,系统就不会响应任何外部可屏蔽中断了。但实际结果却不是这样。我哪里理解错了呢?请各位指点,多谢!
解答:
写了一段kernel module和 userspace program来验证:
kernel module: my_spin_lock.c
- #include <linux/kernel.h>
- #include <linux/init.h>
- #include <linux/module.h>
- #include <linux/spinlock.h>
- #define IF_MASK 0x00000200
- static spinlock_t my_spinlock;
- static unsigned int is_interrupt_enable()
- {
- unsigned long my_eflags;
- asm volatile ("pushfl /n/t"
- "popl %0"
- :"=a"(my_eflags));
- return (((my_eflags & IF_MASK) == 0) ? 0 : 1);
- }
- static int __init init_test()
- {
- unsigned long flags;
- spin_lock_init(&my_spinlock);
- spin_lock_irqsave(&my_spinlock, flags);
- printk("from kernelspace init: interrupt was enable : %d/n", is_interrupt_enable());
- return 0;
- }
- static void __exit init_exit()
- {
- return;
- }
- MODULE_LICENSE("GPL");
- module_init(init_test);
- module_exit(init_exit);
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编译以后生成my_spin_lock.ko
然后再写一段userspace program : test.c
- #include <stdio.h>
- #include <stdlib.h>
- #define IF_MASK 0x00000200
- #define CMD_LEN 100
- unsigned int is_interrupt_enable()
- {
- unsigned long my_eflags;
- asm volatile ("pushfl /n/t"
- "popl %0 /n/t"
- :"=a"(my_eflags));
- return (((my_eflags & IF_MASK) == 0) ? 0 : 1);
- }
- int main (int argc, char *argv[])
- {
- if (argc != 2)
- {
- printf("usersage: insmod your_kernel_module/n");
- return 0;
- }
- char cmd[CMD_LEN];
- memset(cmd, 0, sizeof(cmd));
- sprintf(cmd, "insmod %s", argv[1]);
- printf("from userspace, before insmod, inerrput is enable : %d/n", is_interrupt_enable());
- system(cmd); /*insmod kernel module*/
- printf("from userspace, after insmod, interrupt is enable : %d/n", is_interrupt_enable());
- memset(cmd, 0, sizeof(cmd));
- sprintf(cmd, "rmmod %s", argv[1]);
- system(cmd); /*rmmod kernel module*/
- return 0;
- }
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编译以后生成test二进制文件
然后下命令:
- ./test my_spin_lock.ko
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运行结果:
QUOTE:
from userspace, before insmod, interrupt is enable : 1
from kernelspace init: interrupt was enable : 0
from userspace, after insmod, interrupt is enable: 1
from kernelspace init: interrupt was enable : 0
from userspace, after insmod, interrupt is enable: 1
可见,运行了kernel module的init函数以后,interrupt确实被禁止了。然后返回到用户态,interrupt被打开了。