进程管理模块
一：Linux内核目录结构
arch:不同平台体系结构的相关代码
block:设备驱动
documentation:描述模块功能和协议规范
drivers:驱动程序（USB总线、PCI总线、网上卡、显卡等）
fs:虚拟文件系统VFS代码
include:内核源码依赖的大部头文件
init:内核初始化代码，直接关联到内存积组件入口
ipc:进程间通信实现
kernel:内核核心代码（进程管理、IRQ管理等）
lib:C标准库的子集
licenses:Linux内核根据Licenses/preferred/GPL-2.0中提供GNU通用公共许可版本2
mm:内存管理相关实现操作
net:网络协议代码（TCP、IPv6、Wifi等）
samples:内核实例代码
sound:声卡驱动源码
tools:与内核交互
usr:用户打包和压缩内核的实现的源码
virt:/kvm虚拟化目录相关实现
二.进程概念
1.进程
操作系统作为硬件的使用层，提供使用硬件资源的能力，进程作为操作系统使用层，提供使用操作系统抽象出的资源层的能力。
进程：是指计算机中已运行的程序。进程本身不是基本的运行单位，而是线程的容器。程序本身只是指令、数据及其组织形式的描述，进程才是程序（那些指令和数据）的真正运行实例。
Linux内核把进程叫做任务（task），进程的虚拟地址空间可分为用户虚拟地址空间和内核虚拟地址空间，所有进程共享内核虚拟地址空间，每个进程有独立的用户虚拟地址空间。
2.Linux进程状态命令
ps命令用于输出当前系统的进程状态。显示瞬间进程的状态，并不是动态连续；如果我们想对进程进行实时进程监控就top命令。
3.进程生命周期
Linux操作系统属于多任务操作系统，系统中的每个进程能够分时复用CPU时间片，通过有效的进程调度策略实现多任务并行执行。而进程在被CPU调度运行，等待CPU资源分配以及等待外部事件时会属于不同的状态。进程状态如下：
创建状态：创建新进程；
就绪状态：进程获取可以运作所有资源及准备相关条件；
执行状态：进程正在CPU中执行操作；
阻塞状态：进程因等待某些资源而被跳出CPU；
终止状态：进程消亡。
4.进程有两种特殊形式
没有用户虚拟地址空间的进程叫内核线程，共享用户虚拟地址空间的进程叫用户线程。共享同一个用户虚拟地址空间的所有用户线程叫线程组。
C语言标准库进程 Linux内核进程
包括多个线程的进程 线程组
只有一个线程的进程 任务或进程
线程 共享用户虚拟地址空间的进程
5.Linux内核提供API函数来设置进程状态
TASK_RUNING（可运行状态或者可就绪状态）
TASK_INTERRUPTIBLE（可中断睡眠状态，又叫浅睡眠状态）
TASK_UNINTERUPTIBLE（不可中断状态，又叫深度睡眠状态，我们可以通过ps命令查看被标记为D状态的进程）
TASK_STOPPED（终止状态）
EXIT_ZOMBIE（僵尸状态）
6.进程优先级
进程调度策略和优先级
int prio;
int static_prio;
int normal_prio;
unsigned int rt_priority;
-
prio：进程的当前优先级。这是一个动态值，会根据进程的行为和调度算法进行调整。 -
static_prio：进程的静态优先级。这是进程的基本优先级，一般在创建进程时指定，并且不会随着进程的行为而改变。 -
normal_prio：进程的普通优先级。这是优先级的一个中间值，用于确保进程在运行队列中的相对顺序。 -
rt_priority：实时进程的优先级。对于实时进程，可以设置一个较高的优先级，以便它们能够在其他进程之前得到更多的CPU时间。
进程调度策略可以是多种类型，常见的包括：
-
先进先出（FIFO）：按照进程到达的顺序进行调度，先到达的进程先执行。
-
轮转（Round Robin）：每个进程被分配一个时间片，在时间片用完后，进程被暂停并排队等待下一个时间片。
-
最短作业优先（SJF）：选择剩余执行时间最短的进程，以最小化平均等待时间。
-
最高响应比优先（HRRN）：根据响应比来选择下一个执行的进程，响应比定义为等待时间加上服务时间的比值。
-
实时调度策略：用于实时任务，包括实时先进先出（RT-FIFO）和实时轮转（RT-RR）等。
7.内核线程
独立运行在内核空间的进程，与普通用户进程区别在于内核线程没有独立的进程地址空间。task_struct数据结构里面有一个成员指针mm设置为NULL，它只能运行在内核空间。
三.进程调度CFS及调度类
1.调度
按照某种调度的算法设计，从进程的就绪队列当中选取进程分配CPU，主要是协调对CPU等等相关的资源使用。进程调度目的：最大限度利用CPU时间。如果调度器支持就绪状态切换到执行状态，同时支持执行状态切换到就绪状态，称该调度器为抢占式调度器。
2.调度器类可分为五种
extern const struct sched_class stop_sched_class; // 停机调度类
extern const struct sched_class dl_sched_class; // 限期调度类
extern const struct sched_class rt_sched_class; // 实时调度类
extern const struct sched_class fair_sched_class; // 公平调度类
extern const struct sched_class idle_sched_class; // 空闲调度类
这5种调度类的优先级从高到低依次为：停机调度类–>限期调度类–>实时调度类–>公平调度类–>空闲调度类。
3.进程分类
实时进程：优先级高、需要立即被执行的进程。
普通进程：优先级低、更长执行时间的进程。
进程的优先级是一个0–139的整数直接来表示，数字越小优先级越高，其中优先级0-99留给实时进程，100-139留给普通进程。
4.内核调度策略
Linux内核提供一些调度策略供用户应用程序来选择调度器，Linux内核调度策略源码如下：
// Linux内核调度策略
#define SCHED_NORMAL 0 // 普通进程调度策略
#define SCHED_FIFO 1 // 实时进程调度策略
#define SCHED_RR 2 // 实时进程调度策略
#define SCHED_BATCH 3 // 普通进程调度策略
/* SCHED_ISO: reserved but not implemented yet */
#define SCHED_IDLE 5 // 普通进程调度策略
#define SCHED_DEADLINE 6 // 限期进程调度策略
四.RCU机制及内存优化屏障
1.RCU机制
应用场景是链表，有效地提高遍历读取数据的效率，读取链表有成员数据时候通常只需要rcu_read_lock()，允许多个线程同时读取链表，并且允许一个线程同时修改链表。
2.RCU读-复制-更新
读拷贝更新（RCU）模式添加链表项对应函数list_add_rcu(…)。
读拷贝更新（RCU）模式删除链表项对应函数list_del_rcu(…)。读拷贝更新（RCU）模式更新链表项list_repalce_rcu(…)。
在整个操作过程中，有时要防止编译器和CPU优先代码执行顺序，smp_wmb()保证在它之前的两行代码执行完毕之后再执行后两行。
3.编译器优化
为提高系统性能，编译器在不影响逻辑的情况下会调整指令的执行顺序。
4.CPU执行优化
为提高流水线的性能，CPU的乱序执行可能会让后面的寄存器冲突的指令先于前面指令完成。
5.内存屏障
内存屏障是一种保证内存访问顺序的方法，解决内存访问乱序问题.
6GCC编译器定义的宏
/* The “volatile” is due to gcc bugs */
#define barrier() asm volatile(“”: : :“memory”)
关键字为__volatile__告诉编译器：禁止优化代码，不需要改变barrier()前面的代码块、barrier和后面代码块这3个代码块的顺序。
7.处理器内存屏障
处理器内存屏障解决CPU之间的内存访问乱序问题和处理器访问外围设备的乱序问题。
内存屏障类型 强制性的内存屏障 SMP内存屏障
通用内存屏障 mb() smp_mb()
写内存屏障 wmb() smp_wmb()
读内存屏障 rmb() smp_rmb()
数据依赖屏障 read_barrier_depends() smp_read_barrier_depends()
除数据依赖屏障之外，所有处理器内存屏障隐含编译器优化屏障。
三.task_struct数据结构分析
进程是操作系统调度的一个实体，需要对进程所必须资源做一个抽象化，此抽象化为进程控制块（PCB，Process Control BLock），在Linux内核里面采用task_struct结构体来描述进程控制块。Linux内核涉及进程和程序的所有算法都围绕名为task_struct的数据结构而建立操作。具体Linux内核源码task_struct结构体核心成员如下：
// 进程描述符
struct task_struct {
#ifdef CONFIG_THREAD_INFO_IN_TASK
/*
* For reasons of header soup (see current_thread_info()), this
* must be the first element of task_struct.
*/
struct thread_info thread_info;
#endif
/* -1 unrunnable, 0 runnable, >0 stopped: */
volatile long state; // 判断进程的状态标志
/*
* This begins the randomizable portion of task_struct. Only
* scheduling-critical items should be added above here.
*/
randomized_struct_fields_start
void *stack; // 指向内核栈
refcount_t usage;
/* Per task flags (PF_*), defined further below: */
unsigned int flags;
unsigned int ptrace;
#ifdef CONFIG_SMP
struct llist_node wake_entry;
int on_cpu;
#ifdef CONFIG_THREAD_INFO_IN_TASK
/* Current CPU: */
unsigned int cpu;
#endif
unsigned int wakee_flips;
unsigned long wakee_flip_decay_ts;
struct task_struct *last_wakee;
/*
* recent_used_cpu is initially set as the last CPU used by a task
* that wakes affine another task. Waker/wakee relationships can
* push tasks around a CPU where each wakeup moves to the next one.
* Tracking a recently used CPU allows a quick search for a recently
* used CPU that may be idle.
*/
int recent_used_cpu;
int wake_cpu;
#endif
int on_rq;
// 下面4个成功为：进程调度策略和优先级
int prio;
int static_prio;
int normal_prio;
unsigned int rt_priority;
const struct sched_class *sched_class;
struct sched_entity se;
struct sched_rt_entity rt;
#ifdef CONFIG_CGROUP_SCHED
struct task_group *sched_task_group;
#endif
struct sched_dl_entity dl;
#ifdef CONFIG_UCLAMP_TASK
/* Clamp values requested for a scheduling entity */
struct uclamp_se uclamp_req[UCLAMP_CNT];
/* Effective clamp values used for a scheduling entity */
struct uclamp_se uclamp[UCLAMP_CNT];
#endif
#ifdef CONFIG_PREEMPT_NOTIFIERS
/* List of struct preempt_notifier: */
struct hlist_head preempt_notifiers;
#endif
#ifdef CONFIG_BLK_DEV_IO_TRACE
unsigned int btrace_seq;
#endif
unsigned int policy;
int nr_cpus_allowed;
const cpumask_t *cpus_ptr;
cpumask_t cpus_mask;
#ifdef CONFIG_PREEMPT_RCU
int rcu_read_lock_nesting;
union rcu_special rcu_read_unlock_special;
struct list_head rcu_node_entry;
struct rcu_node *rcu_blocked_node;
#endif /* #ifdef CONFIG_PREEMPT_RCU */
#ifdef CONFIG_TASKS_RCU
unsigned long rcu_tasks_nvcsw;
u8 rcu_tasks_holdout;
u8 rcu_tasks_idx;
int rcu_tasks_idle_cpu;
struct list_head rcu_tasks_holdout_list;
#endif /* #ifdef CONFIG_TASKS_RCU */
struct sched_info sched_info;
struct list_head tasks;
#ifdef CONFIG_SMP
struct plist_node pushable_tasks;
struct rb_node pushable_dl_tasks;
#endif
// 这两个指针指向内存描述符。
// 进程：mm/active_mm 指向同一个内存描述符
// 内核线程：mm是空指针
// 当内核线程执行时，active_mm指向从进程借用内存描述符
struct mm_struct *mm;
struct mm_struct *active_mm;
/* Per-thread vma caching: */
struct vmacache vmacache;
#ifdef SPLIT_RSS_COUNTING
struct task_rss_stat rss_stat;
#endif
int exit_state;
int exit_code;
int exit_signal;
/* The signal sent when the parent dies: */
int pdeath_signal;
/* JOBCTL_*, siglock protected: */
unsigned long jobctl;
/* Used for emulating ABI behavior of previous Linux versions: */
unsigned int personality;
/* Scheduler bits, serialized by scheduler locks: */
unsigned sched_reset_on_fork:1;
unsigned sched_contributes_to_load:1;
unsigned sched_migrated:1;
unsigned sched_remote_wakeup:1;
#ifdef CONFIG_PSI
unsigned sched_psi_wake_requeue:1;
#endif
/* Force alignment to the next boundary: */
unsigned :0;
/* Unserialized, strictly 'current' */
/* Bit to tell LSMs we're in execve(): */
unsigned in_execve:1;
unsigned in_iowait:1;
#ifndef TIF_RESTORE_SIGMASK
unsigned restore_sigmask:1;
#endif
#ifdef CONFIG_MEMCG
unsigned in_user_fault:1;
#endif
#ifdef CONFIG_COMPAT_BRK
unsigned brk_randomized:1;
#endif
#ifdef CONFIG_CGROUPS
/* disallow userland-initiated cgroup migration */
unsigned no_cgroup_migration:1;
/* task is frozen/stopped (used by the cgroup freezer) */
unsigned frozen:1;
#endif
#ifdef CONFIG_BLK_CGROUP
/* to be used once the psi infrastructure lands upstream. */
unsigned use_memdelay:1;
#endif
unsigned long atomic_flags; /* Flags requiring atomic access. */
struct restart_block restart_block;
// 全局的进程号
// 全局的线程组标识符
pid_t pid;
pid_t tgid;
#ifdef CONFIG_STACKPROTECTOR
/* Canary value for the -fstack-protector GCC feature: */
unsigned long stack_canary;
#endif
/*
* Pointers to the (original) parent process, youngest child, younger sibling,
* older sibling, respectively. (p->father can be replaced with
* p->real_parent->pid)
*/
/* Real parent process: */
struct task_struct __rcu *real_parent; // 指向真实的父进程
/* Recipient of SIGCHLD, wait4() reports: */ // 指向父进程
struct task_struct __rcu *parent;
/*
* Children/sibling form the list of natural children:
*/
struct list_head children;
struct list_head sibling;
struct task_struct *group_leader; // 指向线程组的组长
/*
* 'ptraced' is the list of tasks this task is using ptrace() on.
*
* This includes both natural children and PTRACE_ATTACH targets.
* 'ptrace_entry' is this task's link on the p->parent->ptraced list.
*/
struct list_head ptraced;
struct list_head ptrace_entry;
/* PID/PID hash table linkage. */
struct pid *thread_pid;
struct hlist_node pid_links[PIDTYPE_MAX];
struct list_head thread_group;
struct list_head thread_node;
struct completion *vfork_done;
/* CLONE_CHILD_SETTID: */
int __user *set_child_tid;
/* CLONE_CHILD_CLEARTID: */
int __user *clear_child_tid;
u64 utime;
u64 stime;
#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
u64 utimescaled;
u64 stimescaled;
#endif
u64 gtime;
struct prev_cputime prev_cputime;
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
struct vtime vtime;
#endif
#ifdef CONFIG_NO_HZ_FULL
atomic_t tick_dep_mask;
#endif
/* Context switch counts: */
unsigned long nvcsw;
unsigned long nivcsw;
/* Monotonic time in nsecs: */
u64 start_time;
/* Boot based time in nsecs: */
u64 start_boottime;
/* MM fault and swap info: this can arguably be seen as either mm-specific or thread-specific: */
unsigned long min_flt;
unsigned long maj_flt;
/* Empty if CONFIG_POSIX_CPUTIMERS=n */
struct posix_cputimers posix_cputimers;
/* Process credentials: */
/* Tracer's credentials at attach: */
const struct cred __rcu *ptracer_cred;
/* Objective and real subjective task credentials (COW): */
const struct cred __rcu *real_cred;
/* Effective (overridable) subjective task credentials (COW): */
const struct cred __rcu *cred;
#ifdef CONFIG_KEYS
/* Cached requested key. */
struct key *cached_requested_key;
#endif
/*
* executable name, excluding path.
*
* - normally initialized setup_new_exec()
* - access it with [gs]et_task_comm()
* - lock it with task_lock()
*/
char comm[TASK_COMM_LEN];
struct nameidata *nameidata;
// 用于UNIX系统：信号量和共享内存
#ifdef CONFIG_SYSVIPC
struct sysv_sem sysvsem;
struct sysv_shm sysvshm;
#endif
#ifdef CONFIG_DETECT_HUNG_TASK
unsigned long last_switch_count;
unsigned long last_switch_time;
#endif
/* Filesystem information: */
struct fs_struct *fs; // 该成员文件系统信息，主要是进程的根目录和当前工作目录
/* Open file information: */
struct files_struct *files; // 打开文件列表
/* Namespaces: */
struct nsproxy *nsproxy;
/* Signal handlers: */
struct signal_struct *signal;
struct sighand_struct __rcu *sighand;
sigset_t blocked;
sigset_t real_blocked;
/* Restored if set_restore_sigmask() was used: */
sigset_t saved_sigmask;
struct sigpending pending;
unsigned long sas_ss_sp;
size_t sas_ss_size;
unsigned int sas_ss_flags;
struct callback_head *task_works;
#ifdef CONFIG_AUDIT
#ifdef CONFIG_AUDITSYSCALL
struct audit_context *audit_context;
#endif
kuid_t loginuid;
unsigned int sessionid;
#endif
struct seccomp seccomp;
/* Thread group tracking: */
u64 parent_exec_id;
u64 self_exec_id;
/* Protection against (de-)allocation: mm, files, fs, tty, keyrings, mems_allowed, mempolicy: */
spinlock_t alloc_lock;
/* Protection of the PI data structures: */
raw_spinlock_t pi_lock;
struct wake_q_node wake_q;
#ifdef CONFIG_RT_MUTEXES
/* PI waiters blocked on a rt_mutex held by this task: */
struct rb_root_cached pi_waiters;
/* Updated under owner's pi_lock and rq lock */
struct task_struct *pi_top_task;
/* Deadlock detection and priority inheritance handling: */
struct rt_mutex_waiter *pi_blocked_on;
#endif
#ifdef CONFIG_DEBUG_MUTEXES
/* Mutex deadlock detection: */
struct mutex_waiter *blocked_on;
#endif
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
int non_block_count;
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
unsigned int irq_events;
unsigned long hardirq_enable_ip;
unsigned long hardirq_disable_ip;
unsigned int hardirq_enable_event;
unsigned int hardirq_disable_event;
int hardirqs_enabled;
int hardirq_context;
unsigned long softirq_disable_ip;
unsigned long softirq_enable_ip;
unsigned int softirq_disable_event;
unsigned int softirq_enable_event;
int softirqs_enabled;
int softirq_context;
#endif
#ifdef CONFIG_LOCKDEP
# define MAX_LOCK_DEPTH 48UL
u64 curr_chain_key;
int lockdep_depth;
unsigned int lockdep_recursion;
struct held_lock held_locks[MAX_LOCK_DEPTH];
#endif
#ifdef CONFIG_UBSAN
unsigned int in_ubsan;
#endif
/* Journalling filesystem info: */
void *journal_info;
/* Stacked block device info: */
struct bio_list *bio_list;
#ifdef CONFIG_BLOCK
/* Stack plugging: */
struct blk_plug *plug;
#endif
/* VM state: */
struct reclaim_state *reclaim_state;
struct backing_dev_info *backing_dev_info;
struct io_context *io_context;
#ifdef CONFIG_COMPACTION
struct capture_control *capture_control;
#endif
/* Ptrace state: */
unsigned long ptrace_message;
kernel_siginfo_t *last_siginfo;
struct task_io_accounting ioac;
#ifdef CONFIG_PSI
/* Pressure stall state */
unsigned int psi_flags;
#endif
#ifdef CONFIG_TASK_XACCT
/* Accumulated RSS usage: */
u64 acct_rss_mem1;
/* Accumulated virtual memory usage: */
u64 acct_vm_mem1;
/* stime + utime since last update: */
u64 acct_timexpd;
#endif
#ifdef CONFIG_CPUSETS
/* Protected by ->alloc_lock: */
nodemask_t mems_allowed;
/* Seqence number to catch updates: */
seqcount_t mems_allowed_seq;
int cpuset_mem_spread_rotor;
int cpuset_slab_spread_rotor;
#endif
#ifdef CONFIG_CGROUPS
/* Control Group info protected by css_set_lock: */
struct css_set __rcu *cgroups;
/* cg_list protected by css_set_lock and tsk->alloc_lock: */
struct list_head cg_list;
#endif
#ifdef CONFIG_X86_CPU_RESCTRL
u32 closid;
u32 rmid;
#endif
#ifdef CONFIG_FUTEX
struct robust_list_head __user *robust_list;
#ifdef CONFIG_COMPAT
struct compat_robust_list_head __user *compat_robust_list;
#endif
struct list_head pi_state_list;
struct futex_pi_state *pi_state_cache;
struct mutex futex_exit_mutex;
unsigned int futex_state;
#endif
#ifdef CONFIG_PERF_EVENTS
struct perf_event_context *perf_event_ctxp[perf_nr_task_contexts];
struct mutex perf_event_mutex;
struct list_head perf_event_list;
#endif
#ifdef CONFIG_DEBUG_PREEMPT
unsigned long preempt_disable_ip;
#endif
#ifdef CONFIG_NUMA
/* Protected by alloc_lock: */
struct mempolicy *mempolicy;
short il_prev;
short pref_node_fork;
#endif
#ifdef CONFIG_NUMA_BALANCING
int numa_scan_seq;
unsigned int numa_scan_period;
unsigned int numa_scan_period_max;
int numa_preferred_nid;
unsigned long numa_migrate_retry;
/* Migration stamp: */
u64 node_stamp;
u64 last_task_numa_placement;
u64 last_sum_exec_runtime;
struct callback_head numa_work;
/*
* This pointer is only modified for current in syscall and
* pagefault context (and for tasks being destroyed), so it can be read
* from any of the following contexts:
* - RCU read-side critical section
* - current->numa_group from everywhere
* - task's runqueue locked, task not running
*/
struct numa_group __rcu *numa_group;
/*
* numa_faults is an array split into four regions:
* faults_memory, faults_cpu, faults_memory_buffer, faults_cpu_buffer
* in this precise order.
*
* faults_memory: Exponential decaying average of faults on a per-node
* basis. Scheduling placement decisions are made based on these
* counts. The values remain static for the duration of a PTE scan.
* faults_cpu: Track the nodes the process was running on when a NUMA
* hinting fault was incurred.
* faults_memory_buffer and faults_cpu_buffer: Record faults per node
* during the current scan window. When the scan completes, the counts
* in faults_memory and faults_cpu decay and these values are copied.
*/
unsigned long *numa_faults;
unsigned long total_numa_faults;
/*
* numa_faults_locality tracks if faults recorded during the last
* scan window were remote/local or failed to migrate. The task scan
* period is adapted based on the locality of the faults with different
* weights depending on whether they were shared or private faults
*/
unsigned long numa_faults_locality[3];
unsigned long numa_pages_migrated;
#endif /* CONFIG_NUMA_BALANCING */
#ifdef CONFIG_RSEQ
struct rseq __user *rseq;
u32 rseq_sig;
/*
* RmW on rseq_event_mask must be performed atomically
* with respect to preemption.
*/
unsigned long rseq_event_mask;
#endif
struct tlbflush_unmap_batch tlb_ubc;
union {
refcount_t rcu_users;
struct rcu_head rcu;
};
/* Cache last used pipe for splice(): */
struct pipe_inode_info *splice_pipe;
struct page_frag task_frag;
#ifdef CONFIG_TASK_DELAY_ACCT
struct task_delay_info *delays;
#endif
#ifdef CONFIG_FAULT_INJECTION
int make_it_fail;
unsigned int fail_nth;
#endif
/*
* When (nr_dirtied >= nr_dirtied_pause), it's time to call
* balance_dirty_pages() for a dirty throttling pause:
*/
int nr_dirtied;
int nr_dirtied_pause;
/* Start of a write-and-pause period: */
unsigned long dirty_paused_when;
#ifdef CONFIG_LATENCYTOP
int latency_record_count;
struct latency_record latency_record[LT_SAVECOUNT];
#endif
/*
* Time slack values; these are used to round up poll() and
* select() etc timeout values. These are in nanoseconds.
*/
u64 timer_slack_ns;
u64 default_timer_slack_ns;
#ifdef CONFIG_KASAN
unsigned int kasan_depth;
#endif
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/* Index of current stored address in ret_stack: */
int curr_ret_stack;
int curr_ret_depth;
/* Stack of return addresses for return function tracing: */
struct ftrace_ret_stack *ret_stack;
/* Timestamp for last schedule: */
unsigned long long ftrace_timestamp;
/*
* Number of functions that haven't been traced
* because of depth overrun:
*/
atomic_t trace_overrun;
/* Pause tracing: */
atomic_t tracing_graph_pause;
#endif
#ifdef CONFIG_TRACING
/* State flags for use by tracers: */
unsigned long trace;
/* Bitmask and counter of trace recursion: */
unsigned long trace_recursion;
#endif /* CONFIG_TRACING */
#ifdef CONFIG_KCOV
/* See kernel/kcov.c for more details. */
/* Coverage collection mode enabled for this task (0 if disabled): */
unsigned int kcov_mode;
/* Size of the kcov_area: */
unsigned int kcov_size;
/* Buffer for coverage collection: */
void *kcov_area;
/* KCOV descriptor wired with this task or NULL: */
struct kcov *kcov;
/* KCOV common handle for remote coverage collection: */
u64 kcov_handle;
/* KCOV sequence number: */
int kcov_sequence;
#endif
#ifdef CONFIG_MEMCG
struct mem_cgroup *memcg_in_oom;
gfp_t memcg_oom_gfp_mask;
int memcg_oom_order;
/* Number of pages to reclaim on returning to userland: */
unsigned int memcg_nr_pages_over_high;
/* Used by memcontrol for targeted memcg charge: */
struct mem_cgroup *active_memcg;
#endif
#ifdef CONFIG_BLK_CGROUP
struct request_queue *throttle_queue;
#endif
#ifdef CONFIG_UPROBES
struct uprobe_task *utask;
#endif
#if defined(CONFIG_BCACHE) || defined(CONFIG_BCACHE_MODULE)
unsigned int sequential_io;
unsigned int sequential_io_avg;
#endif
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
unsigned long task_state_change;
#endif
int pagefault_disabled;
#ifdef CONFIG_MMU
struct task_struct *oom_reaper_list;
#endif
#ifdef CONFIG_VMAP_STACK
struct vm_struct *stack_vm_area;
#endif
#ifdef CONFIG_THREAD_INFO_IN_TASK
/* A live task holds one reference: */
refcount_t stack_refcount;
#endif
#ifdef CONFIG_LIVEPATCH
int patch_state;
#endif
#ifdef CONFIG_SECURITY
/* Used by LSM modules for access restriction: */
void *security;
#endif
#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
unsigned long lowest_stack;
unsigned long prev_lowest_stack;
#endif
/*
* New fields for task_struct should be added above here, so that
* they are included in the randomized portion of task_struct.
*/
randomized_struct_fields_end
/* CPU-specific state of this task: */
struct thread_struct thread;
/*
* WARNING: on x86, 'thread_struct' contains a variable-sized
* structure. It *MUST* be at the end of 'task_struct'.
*
* Do not put anything below here!
*/
};