Linux 5.6及以上内核中task->state是否被废弃？编译报错求解

我正在学习Linux设备驱动开发，编写了一段遍历进程并获取进程CPU时间、上下文切换及状态等信息的代码：

#include <linux/init.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/sched/signal.h>
#include <linux/jiffies.h>

MODULE_LICENSE("GPL");

static int __init process_init(void)
{
    struct task_struct *task;

    printk(KERN_INFO "Listing process CPU time and waiting time:\n");

    for_each_process(task)
    {
        // Convert CPU time from clock ticks to seconds
        unsigned long user_time = task->utime / HZ;
        unsigned long system_time = task->stime / HZ;

        // Context switches
        unsigned long voluntary_switches = task->nvcsw;
        unsigned long involuntary_switches = task->nivcsw;

        // Process state (to determine if it's waiting)
        long state = task->state;

        printk(KERN_INFO "Process: %s | PID: %d | User Time: %lus | System Time: %lus | State: %ld | Voluntary CS: %lu | Involuntary CS: %lu\n",
               task->comm, task->pid, user_time, system_time, state, voluntary_switches, involuntary_switches);
    }

    return 0;
}

static void __exit process_exit(void)
{
    printk(KERN_INFO "Exiting process waiting time module\n");
}

module_init(process_init);
module_exit(process_exit);

尝试获取进程状态时出现如下编译错误：

/root/MJ/waiting_time.c:26:28: error: ‘struct task_struct’ has no member named ‘state’; did you mean ‘stats’?
26 | long state = task->state;

移除state相关代码后可正常编译。请问Linux 5.6及以上内核版本中task->state是否已被废弃？该如何解决这个问题？

问题解答 #

1. 关于task->state的废弃情况 #

在Linux 5.6及以上内核版本中，task_struct->state字段确实已被废弃。内核通过重构进程状态管理，将原state字段重命名为__state，并将其标记为内部实现细节，不推荐驱动直接访问。

2. 解决方法 #

推荐使用内核提供的封装函数来安全获取进程状态，或者在必要时直接访问重命名后的__state字段（但需注意兼容性风险）：

方法一：使用辅助函数获取可读状态字符

内核提供了task_state_to_char()函数，可以将进程状态转换为更易读的字符（如R代表运行、S代表睡眠等），修改后的完整代码如下：

#include <linux/init.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/sched/signal.h>
#include <linux/jiffies.h>

MODULE_LICENSE("GPL");

static int __init process_init(void)
{
    struct task_struct *task;

    printk(KERN_INFO "Listing process CPU time and waiting time:\n");

    for_each_process(task)
    {
        // Convert CPU time from clock ticks to seconds
        unsigned long user_time = task->utime / HZ;
        unsigned long system_time = task->stime / HZ;

        // Context switches
        unsigned long voluntary_switches = task->nvcsw;
        unsigned long involuntary_switches = task->nivcsw;

        // 使用辅助函数获取可读进程状态字符
        char state_char = task_state_to_char(task);

        printk(KERN_INFO "Process: %s | PID: %d | User Time: %lus | System Time: %lus | State: %c | Voluntary CS: %lu | Involuntary CS: %lu\n",
               task->comm, task->pid, user_time, system_time, state_char, voluntary_switches, involuntary_switches);
    }

    return 0;
}

static void __exit process_exit(void)
{
    printk(KERN_INFO "Exiting process waiting time module\n");
}

module_init(process_init);
module_exit(process_exit);

方法二：直接访问重命名后的__state字段

如果需要获取原始的状态数值，可以直接访问task->__state，但需注意这是内核内部字段，未来版本可能再次变更，代码片段示例：

// 获取原始状态数值
long state_val = task->__state;

printk(KERN_INFO "... | State: %ld | ...", state_val);

状态字符对应说明 #

task_state_to_char()返回的状态字符对应内核进程状态：

• R: 运行态（Running/Runnable）
• S: 可中断睡眠态（Interruptible Sleep）
• D: 不可中断睡眠态（Uninterruptible Sleep）
• T: 停止态（Stopped）
• Z: 僵尸态（Zombie）
• X: 退出态（Exit）

内容的提问来源于stack exchange，提问作者Thurunu Mihiranga