Linux 模块每秒检查电池状态，更好的检查方式，当前方式 rmmod 不起作用

Question

我正在制作一个每秒进行一次 acpi 调用的 Linux 模块(目前仅持续 20 秒)。我希望它继续每秒进行 acpi 调用，直到它被删除。正如我所拥有的，我将模块放入循环中，如果我确实设置了此循环永远重复，则我无法使用 rmmod 来删除模块。有没有办法为循环设置全局变量？

代码:acpi_call.ko

/* Copyright (c) 2010: Michal Kottman */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/proc_fs.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <acpi/acpi.h>
#include <linux/jiffies.h>
#include <linux/sched.h>

MODULE_LICENSE("GPL");

#define BUFFER_SIZE 256

extern struct proc_dir_entry *acpi_root_dir;
char result_buffer[BUFFER_SIZE];
void do_acpi_call(void);

size_t get_avail_bytes(void) 
{
    return BUFFER_SIZE - strlen(result_buffer);
}

char *get_buffer_end(void) 
{
    return result_buffer + strlen(result_buffer);
}

int __init init_battcheck(void) 
{
    int i;
    if( true )
    {
        for (i=0 ; i < 1 ; i++) 
        {
            do_acpi_call();
            if(result_buffer[3] == '1')
                printk(KERN_INFO "Battery is discharging. %c\n", result_buffer[3]);
            else if(result_buffer[3] == '2')
                printk(KERN_INFO "Battery is charging. %c\n", result_buffer[3]);
            else
                printk(KERN_INFO "Battery is CRITICAL. %c\n", result_buffer[3]);
        }
    }
    return 1;
}

/** Appends the contents of an acpi_object to the result buffer
@param result: An acpi object holding result data
@returns: 0 if the result could fully be saved, a higher value otherwise **/
int acpi_result_to_string(union acpi_object *result) 
{
    if (result->type == ACPI_TYPE_INTEGER) 
    {
        snprintf(get_buffer_end(), get_avail_bytes(),"0x%x", (int)result->integer.value);
    } 
    else if (result->type == ACPI_TYPE_STRING) 
    {
        snprintf(get_buffer_end(), get_avail_bytes(), "\"%*s\"", result->string.length, result->string.pointer);
    } 
    else if (result->type == ACPI_TYPE_BUFFER) 
    {
        int i;
        // do not store more than data if it does not fit. The first element is
        // just 4 chars, but there is also two bytes from the curly brackets
        int show_values = min(result->buffer.length, get_avail_bytes() / 6);

        sprintf(get_buffer_end(), "{");
        for (i = 0; i < show_values; i++)
            sprintf(get_buffer_end(), i == 0 ? "0x%02x" : ", 0x%02x", result->buffer.pointer[i]);

        if (result->buffer.length > show_values)
        {
            // if data was truncated, show a trailing comma if there is space
            snprintf(get_buffer_end(), get_avail_bytes(), ",");
            return 1;
        } 
        else 
        {
            // in case show_values == 0, but the buffer is too small to hold
            // more values (i.e. the buffer cannot have anything more than "{")
            snprintf(get_buffer_end(), get_avail_bytes(), "}");
        }
    } 
    else if (result->type == ACPI_TYPE_PACKAGE) 
    {
        int i;
        sprintf(get_buffer_end(), "[");
        for (i=0; i < result->package.count; i++) 
        {
            if (i > 0)
                snprintf(get_buffer_end(), get_avail_bytes(), ", ");

            // abort if there is no more space available
            if (!get_avail_bytes() || acpi_result_to_string(&result->package.elements[i]))
                return 1;
        }
        snprintf(get_buffer_end(), get_avail_bytes(), "]");
    } 
    else 
    {
        snprintf(get_buffer_end(), get_avail_bytes(), "Object type 0x%x\n", result->type);
    }

    // return 0 if there are still bytes available, 1 otherwise
    return !get_avail_bytes();
}


void do_acpi_call(void)
{
    acpi_status status;
    acpi_handle handle;
    struct acpi_object_list arg;
    struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };

    printk(KERN_INFO "acpi_call: Calling \\_SB.PCI0.LPCB.EC0.BAT0._BST\n");

    // get the handle of the method, must be a fully qualified path
    status = acpi_get_handle(NULL, (acpi_string) "\\_SB.PCI0.LPCB.EC0.BAT0._BST", &handle);

    if (ACPI_FAILURE(status)) 
    {
        snprintf(result_buffer, BUFFER_SIZE, "Error: %s", acpi_format_exception(status));
        printk(KERN_ERR "acpi_call: Cannot get handle: %s\n", result_buffer);
        return;
    }

    // prepare parameters
    arg.count = 0;
    arg.pointer = NULL;

    // call the method
    status = acpi_evaluate_object(handle, NULL, &arg, &buffer);
    if (ACPI_FAILURE(status)) 
    {
        snprintf(result_buffer, BUFFER_SIZE,"Error: %s", acpi_format_exception(status));
        printk(KERN_ERR "acpi_call: Method call failed: %s\n", result_buffer);
        return;
    }

    // reset the result buffer
    *result_buffer = '\0';
    acpi_result_to_string(buffer.pointer);
    kfree(buffer.pointer);

    printk(KERN_INFO "acpi_call: Call successful: %s\n", result_buffer);
}


/** module initialization function */
int __init init_acpi_call(void) 
{
    struct proc_dir_entry *acpi_entry = create_proc_entry("call", 0660, acpi_root_dir);

    strcpy(result_buffer, "not called");

    if (acpi_entry == NULL) 
    {
        printk(KERN_ERR "acpi_call: Couldn't create proc entry\n");
        return -ENOMEM;
    }

    printk(KERN_INFO "acpi_call: Module loaded successfully\n");

    init_battcheck();

    return 0;
}

void __exit unload_acpi_call(void) 
{
    remove_proc_entry("call", acpi_root_dir);
    printk(KERN_INFO "acpi_call: Module unloaded successfully\n");
}

module_init(init_acpi_call);
module_exit(unload_acpi_call);

编辑:我刚刚意识到每次调用 do_acpi_call 时我都不需要等待一秒钟，我让它这样做只是为了检查错误。这只是我正在制作的一个例子。我问是否有一种方法可以删除我所描述的循环中的模块？

Answer 1

设置并使用工作队列。这将安排您想要在未来一段时间内运行的工作。在 Linux 设备驱动程序中阅读相关内容: http://lwn.net/images/pdf/LDD3/ch07.pdf

当异步任务开始在您的内核模块中运行时，您需要非常小心地避免竞争条件并仔细清理。也就是说，在模块删除时，取消任何未完成的工作，等待任何正在进行的作业完成(确保作业不会重新安排自身)，然后销毁工作队列，然后才关闭工作函数可能想要使用的任何资源。