kenel thread

本文探讨了Linux Kernel中kthreaddTask的作用及其与kernel_thread的区别,并介绍了平台休眠操作及系统睡眠状态管理的相关回调函数。

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再來就是本文主要談的kthreaddTask,這是在LinuxKernel 2.6所引入的機制,在這之前要產生KernelThread需直接使用函式kernel_thread,而所產生的KernelThread父行程會是當下產生KernelThread的行程(或該父行程結束後,改為initTask(PID=1)).kthreadd的機制下,UserModeKernelMode Task的產生方式做了調整,並讓kthreaddTask成為使用kthread_create產生的KernelThread統一的父行程.也因此,在這機制實現下的LinuxKernel,屬於UserMode行程最上層的父行程為initTask (PID=1),而屬於KernelMode行程最上層的父行程為kthreaddTask (PID=2),而這兩個行程共同的父行程就是idle Task (PID=0).


我們選擇直接透過kernel_thread產生KernelThread,跟透過kthreadd機制相比,兩者的差別在於,一個是由當下呼叫的kernel_threadTask行程所fork出來的,採用kthread_create機制則是由kthreaddTask行程所fork出來的.

kernel_thread

kthread_create

kthread_create_on_node




/**
 * struct platform_hibernation_ops - hibernation platform support
 *
 * The methods in this structure allow a platform to carry out special
 * operations required by it during a hibernation transition.
 *
 * All the methods below, except for @recover(), must be implemented.
 *
 * @begin: Tell the platform driver that we're starting hibernation.
 * Called right after shrinking memory and before freezing devices.
 *
 * @end: Called by the PM core right after resuming devices, to indicate to
 * the platform that the system has returned to the working state.
 *
 * @pre_snapshot: Prepare the platform for creating the hibernation image.
 * Called right after devices have been frozen and before the nonboot
 * CPUs are disabled (runs with IRQs on).
 *
 * @finish: Restore the previous state of the platform after the hibernation
 * image has been created *or* put the platform into the normal operation
 * mode after the hibernation (the same method is executed in both cases).
 * Called right after the nonboot CPUs have been enabled and before
 * thawing devices (runs with IRQs on).
 *
 * @prepare: Prepare the platform for entering the low power state.
 * Called right after the hibernation image has been saved and before
 * devices are prepared for entering the low power state.
 *
 * @enter: Put the system into the low power state after the hibernation image
 * has been saved to disk.
 * Called after the nonboot CPUs have been disabled and all of the low
 * level devices have been shut down (runs with IRQs off).
 *
 * @leave: Perform the first stage of the cleanup after the system sleep state
 * indicated by @set_target() has been left.
 * Called right after the control has been passed from the boot kernel to
 * the image kernel, before the nonboot CPUs are enabled and before devices
 * are resumed.  Executed with interrupts disabled.
 *
 * @pre_restore: Prepare system for the restoration from a hibernation image.
 * Called right after devices have been frozen and before the nonboot
 * CPUs are disabled (runs with IRQs on).
 *
 * @restore_cleanup: Clean up after a failing image restoration.
 * Called right after the nonboot CPUs have been enabled and before
 * thawing devices (runs with IRQs on).
 *
 * @recover: Recover the platform from a failure to suspend devices.
 * Called by the PM core if the suspending of devices during hibernation
 * fails.  This callback is optional and should only be implemented by
 * platforms which require special recovery actions in that situation.
 */
struct platform_hibernation_ops {
int (*begin)(void);
void (*end)(void);
int (*pre_snapshot)(void);
void (*finish)(void);
int (*prepare)(void);
int (*enter)(void);
void (*leave)(void);
int (*pre_restore)(void);
void (*restore_cleanup)(void);
void (*recover)(void);
};

/**
 * struct platform_suspend_ops - Callbacks for managing platform dependent
 * system sleep states.
 *
 * @valid: Callback to determine if given system sleep state is supported by
 * the platform.
 * Valid (ie. supported) states are advertised in /sys/power/state.  Note
 * that it still may be impossible to enter given system sleep state if the
 * conditions aren't right.
 * There is the %suspend_valid_only_mem function available that can be
 * assigned to this if the platform only supports mem sleep.
 *
 * @begin: Initialise a transition to given system sleep state.
 * @begin() is executed right prior to suspending devices.  The information
 * conveyed to the platform code by @begin() should be disregarded by it as
 * soon as @end() is executed.  If @begin() fails (ie. returns nonzero),
 * @prepare(), @enter() and @finish() will not be called by the PM core.
 * This callback is optional.  However, if it is implemented, the argument
 * passed to @enter() is redundant and should be ignored.
 *
 * @prepare: Prepare the platform for entering the system sleep state indicated
 * by @begin().
 * @prepare() is called right after devices have been suspended (ie. the
 * appropriate .suspend() method has been executed for each device) and
 * before device drivers' late suspend callbacks are executed.  It returns
 * 0 on success or a negative error code otherwise, in which case the
 * system cannot enter the desired sleep state (@prepare_late(), @enter(),
 * and @wake() will not be called in that case).
 *
 * @prepare_late: Finish preparing the platform for entering the system sleep
 * state indicated by @begin().
 * @prepare_late is called before disabling nonboot CPUs and after
 * device drivers' late suspend callbacks have been executed.  It returns
 * 0 on success or a negative error code otherwise, in which case the
 * system cannot enter the desired sleep state (@enter() will not be
 * executed).
 *
 * @enter: Enter the system sleep state indicated by @begin() or represented by
 * the argument if @begin() is not implemented.
 * This callback is mandatory.  It returns 0 on success or a negative
 * error code otherwise, in which case the system cannot enter the desired
 * sleep state.
 *
 * @wake: Called when the system has just left a sleep state, right after
 * the nonboot CPUs have been enabled and before device drivers' early
 * resume callbacks are executed.
 * This callback is optional, but should be implemented by the platforms
 * that implement @prepare_late().  If implemented, it is always called
 * after @prepare_late and @enter(), even if one of them fails.
 *
 * @finish: Finish wake-up of the platform.
 * @finish is called right prior to calling device drivers' regular suspend
 * callbacks.
 * This callback is optional, but should be implemented by the platforms
 * that implement @prepare().  If implemented, it is always called after
 * @enter() and @wake(), even if any of them fails.  It is executed after
 * a failing @prepare.
 *
 * @end: Called by the PM core right after resuming devices, to indicate to
 * the platform that the system has returned to the working state or
 * the transition to the sleep state has been aborted.
 * This callback is optional, but should be implemented by the platforms
 * that implement @begin().  Accordingly, platforms implementing @begin()
 * should also provide a @end() which cleans up transitions aborted before
 * @enter().
 *
 * @recover: Recover the platform from a suspend failure.
 * Called by the PM core if the suspending of devices fails.
 * This callback is optional and should only be implemented by platforms
 * which require special recovery actions in that situation.
 */
struct platform_suspend_ops {
int (*valid)(suspend_state_t state);
int (*begin)(suspend_state_t state);
int (*prepare)(void);
int (*prepare_late)(void);
int (*enter)(suspend_state_t state);
void (*wake)(void);
void (*finish)(void);
void (*end)(void);
void (*recover)(void);
};

platform_hibernation_ops   hibernation流程是会执行里面的函数

platform_suspend_ops        suspend流程(on,standby,mem)会执行里面的流程

### 关于 Kernel Panic 的原因及解决方法 Kernel Panic 是 Linux 系统中的一种严重错误,通常表示内核遇到了无法恢复的错误状态。以下是可能导致 Kernel Panic 的原因及其对应的解决方法: #### 1. **硬件相关问题** 硬件故障是导致 Kernel Panic 的常见原因之一。例如,板载声卡、网卡或 CPU 超线程功能可能引发异常[^2]。 - **解决方法**: - 检查错误日志中的信息,确定引发问题的具体硬件。 - 在 BIOS 中禁用可疑硬件(如超线程功能或板载设备)。 - 系统启动后安装相应的驱动程序,并重新启用硬件。 #### 2. **内存问题** 内存故障也可能导致 Kernel Panic,尤其是当系统尝试访问损坏的内存区域时[^2]。 - **解决方法**: - 重新插拔内存条,确保其连接牢固。 - 尝试更换内存条的位置,排除物理故障的可能性。 #### 3. **驱动程序崩溃** 驱动程序中的错误可能导致软性 Panic(Soft Panic),即模块崩溃但未锁定中断处理例程[^3]。硬性 Panic(Hard Panic)则会直接导致系统崩溃。 - **解决方法**: - 更新或重新编译驱动程序以修复潜在问题。 - 如果问题由特定硬件引起,考虑禁用该硬件并检查是否有更新的驱动支持。 #### 4. **内核配置错误** 在安装或升级内核时,错误的配置可能导致 Kernel Panic。例如,缺少必要的模块或依赖项。 - **解决方法**: - 检查内核配置文件,确保所有必要的模块均已加载。 - 使用 `initramfs` 工具重新生成初始 RAM 文件系统。 #### 5. **使用 notify_chain 机制** Linux 内核提供通知链机制,在 Kernel Panic 时调用预定义的通知函数[^4]。这可以帮助开发者捕获和分析崩溃的原因。 - **解决方法**: - 开发者可以注册自定义的通知函数,以便在 Panic 发生时收集更多信息。 - 示例代码如下: ```c #include <linux/notifier.h> static int my_panic_handler(struct notifier_block *nb, unsigned long action, void *data) { printk(KERN_EMERG "Kernel panic detected - performing clean shutdown\n"); return NOTIFY_DONE; } static struct notifier_block my_panic_nb = { .notifier_call = my_panic_handler, }; static int __init register_panic_notifier(void) { atomic_notifier_chain_register(&panic_notifier_list, &my_panic_nb); return 0; } module_init(register_panic_notifier); ``` #### 6. **其他常见原因** - **文件系统损坏**:根文件系统或其他关键文件系统的损坏可能导致 Panic。 - **解决方法**:使用 `fsck` 工具修复文件系统。 - **内核版本不兼容**:某些应用程序或驱动可能与当前内核版本不兼容。 - **解决方法**:升级或降级内核以匹配软件需求。 --- ###
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