刘文学+原创作品转载请注明出处 http://blog.csdn.net/wdxz6547/article/details/51051866 + 《Linux内核分析》MOOC课程http://mooc.study.163.com/course/USTC-1000029000
本文目的, 跟踪 fork 从用户态到内核态之后返回用户态的整个流程. 最后通过
调试验证该流程.
进程描写叙述块
谈论Linux 进程, 不能绕过 task_struct 数据结构. 该结构定义在
linux/include/linux/sched.h
因为数量代码量很庞大, 其实对此, 仅仅须要大概了解就可以. 以下仅仅列出我自己感觉实用的成员
- volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
- void *stack;
- atomic_t usage;
- unsigned int flags; /* per process flags, defined below */
- struct sched_info sched_info
- struct list_head tasks;
- struct mm_struct *mm, *active_mm;
- int exit_state;
- int exit_code, exit_signal;
- unsigned long atomic_flags; /* Flags needing atomic access. */
- struct restart_block restart_block;
- struct task_struct __rcu real_parent; / real parent process */
- struct task_struct __rcu *parent;
- struct list_head children; /* list of my children */
- struct list_head sibling; /* linkage in my parent’s children list */
struct task_struct group_leader; / threadgroup leader */
struct sched_class *sched_class;
- struct sched_entity se;
- struct pid_link pids[PIDTYPE_MAX];
- struct list_head thread_group;
- struct list_head thread_node;
- pid_t pid;
- pid_t tgid;
- struct sysv_sem sysvsem; //IPC
- struct sysv_shm sysvshm;
- struct nameidata *nameidata;
- struct fs_struct *fs;
- struct files_struct *files;
- void *journal_info;
- struct list_head tasks;
- struct mm_struct *mm, *active_mm;
- struct thread_struct thread;
另一些 pstrace, numa, smp, perf_event, cgroup, 中断跟踪, 信号处理等并非眼下关注的问题.
进程创建
从系统调用部分, 我们已经对系统调用有了主要的了解. 因此, 这里通过对 fork
这个系统调用的学习, 一方面加深对系统调用的理解, 一方面理解进程创建的原理.
首先当用户通过 fork 这个系统调用创建一个新的进程的时候, 首先触发中断 0x80,
系统由用户态跳转到内核态. 内核态首先保存现场, 依据用户态传递的系统调用号,
在这里
查找 sys_call_table 找到 fork 相应的系统处理函数 sys_fork(实际上为
SYSCALL_DEFINE0(fork))
fork 的代码具体实如今这里
首先, 调用 _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0)
而 _do_fork 对 fork 主要实用的两个函数
p = copy_process(clone_flags, stack_start, stack_size,
child_tidptr, NULL, trace, tls);
当 copy_process 运行成功:
1. pid = get_task_pid(p, PIDTYPE_PID); 获取进程 pid
2. wake_up_new_task(p);
至此, 系统调用 fork 返回. 其余部分与系统參照系统调用部分. 以下着重分析
copy_process 和 wake_up_new_task
copy_process
http://code.woboq.org/linux/linux/kernel/fork.c.html#copy_process
static struct task_struct *copy_process(unsigned long clone_flags,
unsigned long stack_start,
unsigned long stack_size,
int __user *child_tidptr,
struct pid *pid,
int trace,
unsigned long tls)
{
int retval;
struct task_struct *p;
//调用 security_hook_heads.task_create 中每个元素 P 的 P->hook.task_create(clone_flags)
retval = security_task_create(clone_flags);
if (retval)
goto fork_out;
retval = -ENOMEM;
//为新的进程分配内核空间, 新进程分配内核堆栈. 之后将 current 拷贝给
//新创建进程 p, 设置相关属性. 并返回 p. 至此, 新进程的空间及内容已经
//就绪.
p = dup_task_struct(current);
if (!p)
goto fork_out;
//初始化 p->pi_lock
rt_mutex_init_task(p);
retval = -EAGAIN;
current->flags &= ~PF_NPROC_EXCEEDED;
//为 p 分配内核空间, 并将 current->cred 拷贝给 p, 并更新 p->cred 相关成员
retval = copy_creds(p, clone_flags);
if (retval < 0)
goto bad_fork_free;
/*
* If multiple threads are within copy_process(), then this check
* triggers too late. This doesn't hurt, the check is only there
* to stop root fork bombs.
*/
retval = -EAGAIN;
if (nr_threads >= max_threads)
goto bad_fork_cleanup_count;
//为 p->delays 分配内核空间并加锁
delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
//以下初始化 p 相关数据成员
p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
p->flags |= PF_FORKNOEXEC;
INIT_LIST_HEAD(&p->children);
INIT_LIST_HEAD(&p->sibling);
rcu_copy_process(p);
p->vfork_done = NULL;
spin_lock_init(&p->alloc_lock);
init_sigpending(&p->pending);
p->utime = p->stime = p->gtime = 0;
p->utimescaled = p->stimescaled = 0;
prev_cputime_init(&p->prev_cputime);
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
seqcount_init(&p->vtime_seqcount);
p->vtime_snap = 0;
p->vtime_snap_whence = VTIME_INACTIVE;
#endif
#if defined(SPLIT_RSS_COUNTING)
memset(&p->rss_stat, 0, sizeof(p->rss_stat));
#endif
p->default_timer_slack_ns = current->timer_slack_ns;
//p->ioac 置零
task_io_accounting_init(&p->ioac);
acct_clear_integrals(p);
posix_cpu_timers_init(p);
p->start_time = ktime_get_ns();
p->real_start_time = ktime_get_boot_ns();
p->io_context = NULL;
p->audit_context = NULL;
threadgroup_change_begin(current);
cgroup_fork(p);
#ifdef CONFIG_NUMA
p->mempolicy = mpol_dup(p->mempolicy);
if (IS_ERR(p->mempolicy)) {
retval = PTR_ERR(p->mempolicy);
p->mempolicy = NULL;
goto bad_fork_cleanup_threadgroup_lock;
}
#endif
#ifdef CONFIG_CPUSETS
p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
seqcount_init(&p->mems_allowed_seq);
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
p->irq_events = 0;
p->hardirqs_enabled = 0;
p->hardirq_enable_ip = 0;
p->hardirq_enable_event = 0;
p->hardirq_disable_ip = _THIS_IP_;
p->hardirq_disable_event = 0;
p->softirqs_enabled = 1;
p->softirq_enable_ip = _THIS_IP_;
p->softirq_enable_event = 0;
p->softirq_disable_ip = 0;
p->softirq_disable_event = 0;
p->hardirq_context = 0;
p->softirq_context = 0;
#endif
p->pagefault_disabled = 0;
#ifdef CONFIG_LOCKDEP
p->lockdep_depth = 0; /* no locks held yet */
p->curr_chain_key = 0;
p->lockdep_recursion = 0;
#endif
#ifdef CONFIG_DEBUG_MUTEXES
p->blocked_on = NULL; /* not blocked yet */
#endif
#ifdef CONFIG_BCACHE
p->sequential_io = 0;
p->sequential_io_avg = 0;
#endif
/* Perform scheduler related setup. Assign this task to a CPU. */
//初始化 sched, numa 相关成员, TODO
retval = sched_fork(clone_flags, p);
if (retval)
goto bad_fork_cleanup_policy;
//初始化 CONFIG_PERF_EVENTS 条件编译中的成员
retval = perf_event_init_task(p);
if (retval)
goto bad_fork_cleanup_policy;
//为成员 audit_context 分配内存并初始化, 并设置 TIF_SYSCALL_AUDIT 标志
retval = audit_alloc(p);
if (retval)
goto bad_fork_cleanup_perf;
/* copy all the process information */
//初始化 p->sysvshm
shm_init_task(p);
retval = copy_semundo(clone_flags, p);
if (retval)
goto bad_fork_cleanup_audit;
//拷贝父进程的 files
retval = copy_files(clone_flags, p);
if (retval)
goto bad_fork_cleanup_semundo;
//拷贝父进程的 fs
retval = copy_fs(clone_flags, p);
if (retval)
goto bad_fork_cleanup_files;
//拷贝父进程的 sighand
retval = copy_sighand(clone_flags, p);
if (retval)
goto bad_fork_cleanup_fs;
//拷贝父进程的 signal
retval = copy_signal(clone_flags, p);
if (retval)
goto bad_fork_cleanup_sighand;
//关键, 拷贝父进程的 mm, TODO 具体分析
retval = copy_mm(clone_flags, p);
if (retval)
goto bad_fork_cleanup_signal;
//创建自己的命名空间
retval = copy_namespaces(clone_flags, p);
if (retval)
goto bad_fork_cleanup_mm;
//拷贝父进程的 io_context
retval = copy_io(clone_flags, p);
if (retval)
goto bad_fork_cleanup_namespaces;
//拷贝父进程的 thread
retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
if (retval)
goto bad_fork_cleanup_io;
if (pid != &init_struct_pid) {
pid = alloc_pid(p->nsproxy->pid_ns_for_children);
if (IS_ERR(pid)) {
retval = PTR_ERR(pid);
goto bad_fork_cleanup_io;
}
}
p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
/*
* Clear TID on mm_release()?
*/
p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
#ifdef CONFIG_BLOCK
p->plug = NULL;
#endif
#ifdef CONFIG_FUTEX
p->robust_list = NULL;
#ifdef CONFIG_COMPAT
p->compat_robust_list = NULL;
#endif
INIT_LIST_HEAD(&p->pi_state_list);
p->pi_state_cache = NULL;
#endif
/*
* sigaltstack should be cleared when sharing the same VM
*/
if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
p->sas_ss_sp = p->sas_ss_size = 0;
/*
* Syscall tracing and stepping should be turned off in the
* child regardless of CLONE_PTRACE.
*/
user_disable_single_step(p);
clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
#ifdef TIF_SYSCALL_EMU
clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
#endif
clear_all_latency_tracing(p);
/* ok, now we should be set up.. */
p->pid = pid_nr(pid);
if (clone_flags & CLONE_THREAD) {
p->exit_signal = -1;
p->group_leader = current->group_leader;
p->tgid = current->tgid;
} else {
if (clone_flags & CLONE_PARENT)
p->exit_signal = current->group_leader->exit_signal;
else
p->exit_signal = (clone_flags & CSIGNAL);
p->group_leader = p;
p->tgid = p->pid;
}
p->nr_dirtied = 0;
p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
p->dirty_paused_when = 0;
p->pdeath_signal = 0;
INIT_LIST_HEAD(&p->thread_group);
p->task_works = NULL;
//兴许 TODO
/*
* Ensure that the cgroup subsystem policies allow the new process to be
* forked. It should be noted the the new process's css_set can be changed
* between here and cgroup_post_fork() if an organisation operation is in
* progress.
*/
retval = cgroup_can_fork(p);
if (retval)
goto bad_fork_free_pid;
/*
* Make it visible to the rest of the system, but dont wake it up yet.
* Need tasklist lock for parent etc handling!
*/
write_lock_irq(&tasklist_lock);
/* CLONE_PARENT re-uses the old parent */
if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
p->real_parent = current->real_parent;
p->parent_exec_id = current->parent_exec_id;
} else {
p->real_parent = current;
p->parent_exec_id = current->self_exec_id;
}
spin_lock(¤t->sighand->siglock);
/*
* Copy seccomp details explicitly here, in case they were changed
* before holding sighand lock.
*/
copy_seccomp(p);
/*
* Process group and session signals need to be delivered to just the
* parent before the fork or both the parent and the child after the
* fork. Restart if a signal comes in before we add the new process to
* it's process group.
* A fatal signal pending means that current will exit, so the new
* thread can't slip out of an OOM kill (or normal SIGKILL).
*/
recalc_sigpending();
if (signal_pending(current)) {
spin_unlock(¤t->sighand->siglock);
write_unlock_irq(&tasklist_lock);
retval = -ERESTARTNOINTR;
goto bad_fork_cancel_cgroup;
}
if (likely(p->pid)) {
ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
init_task_pid(p, PIDTYPE_PID, pid);
if (thread_group_leader(p)) {
init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
init_task_pid(p, PIDTYPE_SID, task_session(current));
if (is_child_reaper(pid)) {
ns_of_pid(pid)->child_reaper = p;
p->signal->flags |= SIGNAL_UNKILLABLE;
}
p->signal->leader_pid = pid;
p->signal->tty = tty_kref_get(current->signal->tty);
list_add_tail(&p->sibling, &p->real_parent->children);
list_add_tail_rcu(&p->tasks, &init_task.tasks);
attach_pid(p, PIDTYPE_PGID);
attach_pid(p, PIDTYPE_SID);
__this_cpu_inc(process_counts);
} else {
current->signal->nr_threads++;
atomic_inc(¤t->signal->live);
atomic_inc(¤t->signal->sigcnt);
list_add_tail_rcu(&p->thread_group,
&p->group_leader->thread_group);
list_add_tail_rcu(&p->thread_node,
&p->signal->thread_head);
}
attach_pid(p, PIDTYPE_PID);
nr_threads++;
}
total_forks++;
spin_unlock(¤t->sighand->siglock);
syscall_tracepoint_update(p);
write_unlock_irq(&tasklist_lock);
proc_fork_connector(p);
cgroup_post_fork(p);
threadgroup_change_end(current);
perf_event_fork(p);
trace_task_newtask(p, clone_flags);
uprobe_copy_process(p, clone_flags);
return p;
bad_fork_cancel_cgroup:
cgroup_cancel_fork(p);
bad_fork_free_pid:
if (pid != &init_struct_pid)
free_pid(pid);
bad_fork_cleanup_io:
if (p->io_context)
exit_io_context(p);
bad_fork_cleanup_namespaces:
exit_task_namespaces(p);
bad_fork_cleanup_mm:
if (p->mm)
mmput(p->mm);
bad_fork_cleanup_signal:
if (!(clone_flags & CLONE_THREAD))
free_signal_struct(p->signal);
bad_fork_cleanup_sighand:
__cleanup_sighand(p->sighand);
bad_fork_cleanup_fs:
exit_fs(p); /* blocking */
bad_fork_cleanup_files:
exit_files(p); /* blocking */
bad_fork_cleanup_semundo:
exit_sem(p);
bad_fork_cleanup_audit:
audit_free(p);
bad_fork_cleanup_perf:
perf_event_free_task(p);
bad_fork_cleanup_policy:
#ifdef CONFIG_NUMA
mpol_put(p->mempolicy);
bad_fork_cleanup_threadgroup_lock:
#endif
threadgroup_change_end(current);
delayacct_tsk_free(p);
bad_fork_cleanup_count:
atomic_dec(&p->cred->user->processes);
exit_creds(p);
bad_fork_free:
free_task(p);
fork_out:
return ERR_PTR(retval);
}dup_task_struct 分析
http://code.woboq.org/linux/linux/kernel/fork.c.html#dup_task_struct
static struct task_struct *dup_task_struct(struct task_struct *orig)
{
struct task_struct *tsk;
struct thread_info *ti;
//对于非 NUMA 架构, 返回 -1
int node = tsk_fork_get_node(orig);
int err;
//为新进程分配内核空间:
// kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
// slab_alloc_node(s, gfpflags, node, _RET_IP_);
//
tsk = alloc_task_struct_node(node);
if (!tsk)
return NULL;
//为新进程分配线程页信息:
// struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP, THREAD_SIZE_ORDER);
// return page ? page_address(page) : NULL;
ti = alloc_thread_info_node(tsk, node);
if (!ti)
goto free_tsk;
//将 tsk 指向 org 的内存地址
// *tsk = *org
err = arch_dup_task_struct(tsk, orig);
if (err)
goto free_ti;
//注意这里 tsk 的 stack 是自己又一次分配的, 而不是共享.
tsk->stack = ti;
#ifdef CONFIG_SECCOMP
/*
* We must handle setting up seccomp filters once we're under
* the sighand lock in case orig has changed between now and
* then. Until then, filter must be NULL to avoid messing up
* the usage counts on the error path calling free_task.
*/
tsk->seccomp.filter = NULL;
#endif
//初始化 task 的栈为 origin 的栈
// tsk->stack = orig->stack
// tsk->stack->task = tsk
setup_thread_stack(tsk, orig);
//置零 tsk->stack->flags 中的 TIF_USER_RETURN_NOTIFY 标志
clear_user_return_notifier(tsk);
//置零 tsk->stack->flags 中的 TIF_NEED_RESCHED 标志
clear_tsk_need_resched(tsk);
//溢出检查
//将 tsk->stack 最后一个自己设置为 STACK_END_MAGIC, 标记 stack 结束
set_task_stack_end_magic(tsk);
#ifdef CONFIG_CC_STACKPROTECTOR
tsk->stack_canary = get_random_int();
#endif
/*
* One for us, one for whoever does the "release_task()" (usually
* parent)
*/
atomic_set(&tsk->usage, 2);
#ifdef CONFIG_BLK_DEV_IO_TRACE
tsk->btrace_seq = 0;
#endif
//设置 task_struct 一些属性
tsk->splice_pipe = NULL;
tsk->task_frag.page = NULL;
tsk->wake_q.next = NULL;
account_kernel_stack(ti, 1);
return tsk;
free_ti:
free_thread_info(ti);
free_tsk:
free_task_struct(tsk);
return NULL;
}wake_up_new_task
/*
* wake_up_new_task - wake up a newly created task for the first time.
*
* This function will do some initial scheduler statistics housekeeping
* that must be done for every newly created context, then puts the task
* on the runqueue and wakes it.
*/
void wake_up_new_task(struct task_struct *p)
{
unsigned long flags;
struct rq *rq;
raw_spin_lock_irqsave(&p->pi_lock, flags);
/* Initialize new task's runnable average */
init_entity_runnable_average(&p->se);
#ifdef CONFIG_SMP
/*
* Fork balancing, do it here and not earlier because:
* - cpus_allowed can change in the fork path
* - any previously selected cpu might disappear through hotplug
*/
set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
#endif
rq = __task_rq_lock(p);
activate_task(rq, p, 0);
p->on_rq = TASK_ON_RQ_QUEUED;
trace_sched_wakeup_new(p);
check_preempt_curr(rq, p, WF_FORK);
#ifdef CONFIG_SMP
if (p->sched_class->task_woken) {
/*
* Nothing relies on rq->lock after this, so its fine to
* drop it.
*/
lockdep_unpin_lock(&rq->lock);
p->sched_class->task_woken(rq, p);
lockdep_pin_lock(&rq->lock);
}
#endif
task_rq_unlock(rq, p, &flags);
}附录
task_struct 中会保留父进程信息的数据成员. 未完待续
struct task_struct {
volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
void *stack;
atomic_t usage;
unsigned int flags; /* per process flags, defined below */
unsigned int ptrace;
#ifdef CONFIG_SMP
struct llist_node wake_entry;
int on_cpu;
unsigned int wakee_flips;
unsigned long wakee_flip_decay_ts;
struct task_struct *last_wakee;
int wake_cpu;
#endif
//prio 父进程的 normal_prio
int prio, static_prio, normal_prio;
unsigned int rt_priority;
const struct sched_class *sched_class;
//重要结构, 非克隆
struct sched_rt_entity rt;
#ifdef CONFIG_CGROUP_SCHED
struct task_group *sched_task_group;
#endif
//重要结构, 非克隆
struct sched_dl_entity dl;
#ifdef CONFIG_BLK_DEV_IO_TRACE
unsigned int btrace_seq;
#endif
unsigned int policy;
int nr_cpus_allowed;
cpumask_t cpus_allowed;
#ifdef CONFIG_TASKS_RCU
unsigned long rcu_tasks_nvcsw;
#endif /* #ifdef CONFIG_TASKS_RCU */
#ifdef CONFIG_SCHED_INFO
struct sched_info sched_info;
#endif
struct list_head tasks;
#ifdef CONFIG_SMP
struct plist_node pushable_tasks;
struct rb_node pushable_dl_tasks;
#endif
struct mm_struct *mm, *active_mm;
/* per-thread vma caching */
u32 vmacache_seqnum;
struct vm_area_struct *vmacache[VMACACHE_SIZE];
/* task state */
int exit_state;
int exit_code, exit_signal;
unsigned long jobctl; /* JOBCTL_*, siglock protected */
/* 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 :0; /* force alignment to the next boundary */
/* unserialized, strictly 'current' */
unsigned in_execve:1; /* bit to tell LSMs we're in execve */
unsigned in_iowait:1;
#ifdef CONFIG_MEMCG
unsigned memcg_may_oom:1;
#ifndef CONFIG_SLOB
unsigned memcg_kmem_skip_account:1;
#endif
#endif
#ifdef CONFIG_COMPAT_BRK
unsigned brk_randomized:1;
#endif
unsigned long atomic_flags; /* Flags needing atomic access. */
struct restart_block restart_block;
pid_t pid;
pid_t tgid;
#ifdef CONFIG_CC_STACKPROTECTOR
/* Canary value for the -fstack-protector gcc feature */
unsigned long stack_canary;
#endif
/*
* pointers to (original) parent process, youngest child, younger sibling,
* older sibling, respectively. (p->father can be replaced with
* p->real_parent->pid)
*/
struct task_struct __rcu *real_parent; /* real parent process */
struct task_struct __rcu *parent; /* recipient of SIGCHLD, wait4() reports */
struct task_struct *group_leader; /* threadgroup leader */
/*
* ptraced is the list of tasks this task is using ptrace on.
* This includes both natural children and PTRACE_ATTACH targets.
* p->ptrace_entry is p's link on the p->parent->ptraced list.
*/
struct list_head ptraced;
struct list_head ptrace_entry;
/* PID/PID hash table linkage. */
struct pid_link pids[PIDTYPE_MAX];
struct list_head thread_node;
unsigned long nvcsw, nivcsw; /* context switch counts */
/* mm fault and swap info: this can arguably be seen as either mm-specific or thread-specific */
unsigned long min_flt, maj_flt;
/* process credentials */
const struct cred __rcu *real_cred; /* objective and real subjective task
* credentials (COW) */
char comm[TASK_COMM_LEN]; /* executable name excluding path
- access with [gs]et_task_comm (which lock
it with task_lock())
- initialized normally by setup_new_exec */
/* file system info */
struct nameidata *nameidata;
#ifdef CONFIG_SYSVIPC
/* ipc stuff */
struct sysv_sem sysvsem;
#endif
#ifdef CONFIG_DETECT_HUNG_TASK
/* hung task detection */
unsigned long last_switch_count;
#endif
/* filesystem information */
struct fs_struct *fs; //拷贝父进程
/* open file information */
struct files_struct *files; //拷贝父进程
/* signal handlers */
//仅拷贝父进程的 signal->rlim, oom_score_adj, oom_score_adj_min, has_child_subreaper 而不是内存.
struct signal_struct *signal;
struct sighand_struct *sighand; //仅拷贝父进程的 sighand->action, 而不是内存.
sigset_t blocked, real_blocked;
sigset_t saved_sigmask; /* restored if set_restore_sigmask() was used */
unsigned long sas_ss_sp;
size_t sas_ss_size;
#ifdef CONFIG_AUDITSYSCALL
kuid_t loginuid;
unsigned int sessionid;
#endif
struct seccomp seccomp;
/* Thread group tracking */
u32 parent_exec_id;
u32 self_exec_id;
/* Protection of (de-)allocation: mm, files, fs, tty, keyrings, mems_allowed,
* mempolicy */
struct wake_q_node wake_q;
#ifdef CONFIG_LOCKDEP
# define MAX_LOCK_DEPTH 48UL
struct held_lock held_locks[MAX_LOCK_DEPTH];
gfp_t lockdep_reclaim_gfp;
#endif
#ifdef CONFIG_UBSAN
unsigned int in_ubsan;
#endif
/* journalling filesystem info */
void *journal_info;
/* stacked block device info */
struct bio_list *bio_list;
/* VM state */
struct reclaim_state *reclaim_state;
struct backing_dev_info *backing_dev_info;
unsigned long ptrace_message;
siginfo_t *last_siginfo; /* For ptrace use. */
#ifdef CONFIG_CPUSETS
nodemask_t mems_allowed; /* Protected by alloc_lock */
#endif
#endif
#ifdef CONFIG_DEBUG_PREEMPT
unsigned long preempt_disable_ip;
#endif
#ifdef CONFIG_NUMA
short il_next;
short pref_node_fork;
#endif
#ifdef CONFIG_NUMA_BALANCING
int numa_scan_seq;
unsigned int numa_scan_period_max;
unsigned long numa_migrate_retry;
struct list_head numa_entry;
/*
* 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 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_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
struct tlbflush_unmap_batch tlb_ubc;
#endif
struct rcu_head rcu;
/*
* cache last used pipe for splice
*/
struct pipe_inode_info *splice_pipe;
struct page_frag task_frag;
#ifdef CONFIG_FAULT_INJECTION
int make_it_fail;
#endif
#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.
*/
unsigned long timer_slack_ns;
unsigned long default_timer_slack_ns; //父进程的 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;
/* Stack of return addresses for return function tracing */
struct ftrace_ret_stack *ret_stack;
/* time stamp 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 for the 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_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;
#endif
#ifdef CONFIG_UPROBES
struct uprobe_task *utask;
#endif
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
unsigned long task_state_change;
#endif
/* CPU-specific state of this task */
struct thread_struct thread; //克隆父进程
/*
* 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!
*/
};