在内核的API里经常能够见到一个指针current，它表示的是当前的进程(如果说是一个全局变量虽然不合理，但更容易理解)，

current内核路径为：include\asm-generic\current.h

current当前进程具体定义：#ifndef __ASM_GENERIC_CURRENT_H

#define __ASM_GENERIC_CURRENT_H

#include

#define get_current() (current_thread_info()->task) //获取当前进程的线程task

#define current get_current() //表示当前进程

#endif /* __ASM_GENERIC_CURRENT_H */

上面get_current()调用了current_thread_info函数，该函数的内核路径为：arch/arm/include/asm/thread_info.hstatic inline struct thread_info *current_thread_info(void) __attribute_const__;

static inline struct thread_info *current_thread_info(void)

{

register unsigned long sp asm ("sp");

return (struct thread_info *)(sp & ~(THREAD_SIZE - 1));

}

关于更详细的说明，详见：点击打开链接

上面通过get_current()获取到了task_task，接下来分析该结构体

task_struct内核路径：include\linux\sched.h

中文注解，详见：点击打开链接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;

#endif

int on_rq;

int prio, static_prio, 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

#ifdef CONFIG_PREEMPT_NOTIFIERS

/* list of struct preempt_notifier: */

struct hlist_head preempt_notifiers;

#endif

/*

* fpu_counter contains the number of consecutive context switches

* that the FPU is used. If this is over a threshold, the lazy fpu

* saving becomes unlazy to save the trap. This is an unsigned char

* so that after 256 times the counter wraps and the behavior turns

* lazy again; this to deal with bursty apps that only use FPU for

* a short time

*/

unsigned char fpu_counter;

#ifdef CONFIG_BLK_DEV_IO_TRACE

unsigned int btrace_seq;

#endif

unsigned int policy;

int nr_cpus_allowed;

cpumask_t cpus_allowed;

#ifdef CONFIG_PREEMPT_RCU

int rcu_read_lock_nesting;

char rcu_read_unlock_special;

struct list_head rcu_node_entry;

#endif /* #ifdef CONFIG_PREEMPT_RCU */

#ifdef CONFIG_TREE_PREEMPT_RCU

struct rcu_node *rcu_blocked_node;

#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */

#ifdef CONFIG_RCU_BOOST

struct rt_mutex *rcu_boost_mutex;

#endif /* #ifdef CONFIG_RCU_BOOST */

#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)

struct sched_info sched_info;

#endif

struct list_head tasks;

#ifdef CONFIG_SMP

struct plist_node pushable_tasks;

#endif

struct mm_struct *mm, *active_mm;

#ifdef CONFIG_COMPAT_BRK

unsigned brk_randomized:1;

#endif

#if defined(SPLIT_RSS_COUNTING)

struct task_rss_statrss_stat;

#endif

/* task state */

int exit_state;

int exit_code, exit_signal;

int pdeath_signal; /* The signal sent when the parent dies */

unsigned int jobctl;/* JOBCTL_*, siglock protected */

/* Used for emulating ABI behavior of previous Linux versions */

unsigned int personality;

unsigned did_exec:1;

unsigned in_execve:1;/* Tell the LSMs that the process is doing an

* execve */

unsigned in_iowait:1;

/* task may not gain privileges */

unsigned no_new_privs:1;

/* Revert to default priority/policy when forking */

unsigned sched_reset_on_fork:1;

unsigned sched_contributes_to_load:1;

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 */

/*

* children/sibling forms the list of my natural children

*/

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 */

/*

* 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_group;

struct list_head thread_node;

struct completion *vfork_done;/* for vfork() */

int __user *set_child_tid;/* CLONE_CHILD_SETTID */

int __user *clear_child_tid;/* CLONE_CHILD_CLEARTID */

cputime_t utime, stime, utimescaled, stimescaled;

cputime_t gtime;

#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE

struct cputime prev_cputime;

#endif

#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN

seqlock_t vtime_seqlock;

unsigned long long vtime_snap;

enum {

VTIME_SLEEPING = 0,

VTIME_USER,

VTIME_SYS,

} vtime_snap_whence;

#endif

unsigned long nvcsw, nivcsw; /* context switch counts */

struct timespec start_time; /* monotonic time */

struct timespec real_start_time;/* boot based time */

/* mm fault and swap info: this can arguably be seen as either mm-specific or thread-specific */

unsigned long min_flt, maj_flt;

struct task_cputime cputime_expires;

struct list_head cpu_timers[3];

/* process credentials */

const struct cred __rcu *real_cred; /* objective and real subjective task

* credentials (COW) */

const struct cred __rcu *cred;/* effective (overridable) 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 */

int link_count, total_link_count;

#ifdef CONFIG_SYSVIPC

/* ipc stuff */

struct sysv_sem sysvsem;

#endif

#ifdef CONFIG_DETECT_HUNG_TASK

/* hung task detection */

unsigned long last_switch_count;

#endif

/* CPU-specific state of this task */

struct thread_struct thread;

/* filesystem information */

struct fs_struct *fs;

/* open file information */

struct files_struct *files;

/* namespaces */

struct nsproxy *nsproxy;

/* signal handlers */

struct signal_struct *signal;

struct sighand_struct *sighand;

sigset_t blocked, real_blocked;

sigset_t saved_sigmask;/* restored if set_restore_sigmask() was used */

struct sigpending pending;

unsigned long sas_ss_sp;

size_t sas_ss_size;

int (*notifier)(void *priv);

void *notifier_data;

sigset_t *notifier_mask;

struct callback_head *task_works;

struct audit_context *audit_context;

#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 */

spinlock_t alloc_lock;

/* Protection of the PI data structures: */

raw_spinlock_t pi_lock;

#ifdef CONFIG_RT_MUTEXES

/* PI waiters blocked on a rt_mutex held by this task */

struct plist_head pi_waiters;

/* 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_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];

gfp_t lockdep_reclaim_gfp;

#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;

unsigned long ptrace_message;

siginfo_t *last_siginfo; /* For ptrace use. */

struct task_io_accounting ioac;

#if defined(CONFIG_TASK_XACCT)

u64 acct_rss_mem1;/* accumulated rss usage */

u64 acct_vm_mem1;/* accumulated virtual memory usage */

cputime_t acct_timexpd;/* stime + utime since last update */

#endif

#ifdef CONFIG_CPUSETS

nodemask_t mems_allowed;/* Protected by alloc_lock */

seqcount_t mems_allowed_seq;/* Seqence no to catch updates */

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_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;

#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_NUMA

struct mempolicy *mempolicy;/* Protected by alloc_lock */

short il_next;

short pref_node_fork;

#endif

#ifdef CONFIG_NUMA_BALANCING

int numa_scan_seq;

int numa_migrate_seq;

unsigned int numa_scan_period;

u64 node_stamp;/* migration stamp */

struct callback_head numa_work;

#endif /* CONFIG_NUMA_BALANCING */

struct rcu_head rcu;

/*

* cache last used pipe for splice

*/

struct pipe_inode_info *splice_pipe;

struct page_frag task_frag;

#ifdefCONFIG_TASK_DELAY_ACCT

struct task_delay_info *delays;

#endif

#ifdef CONFIG_FAULT_INJECTION

int make_it_fail;

#endif

/*

* when (nr_dirtied >= nr_dirtied_pause), it's time to call

* balance_dirty_pages() for some dirty throttling pause

*/

int nr_dirtied;

int nr_dirtied_pause;

unsigned long dirty_paused_when; /* start of a write-and-pause period */

#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;

#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 /* memcg uses this to do batch job */

struct memcg_batch_info {

int do_batch;/* incremented when batch uncharge started */

struct mem_cgroup *memcg; /* target memcg of uncharge */

unsigned long nr_pages;/* uncharged usage */

unsigned long memsw_nr_pages; /* uncharged mem+swap usage */

} memcg_batch;

unsigned int memcg_kmem_skip_account;

struct memcg_oom_info {

struct mem_cgroup *memcg;

gfp_t gfp_mask;

int order;

unsigned int may_oom:1;

} memcg_oom;

#endif

#ifdef CONFIG_HAVE_HW_BREAKPOINT

atomic_t ptrace_bp_refcnt;

#endif

#ifdef CONFIG_UPROBES

struct uprobe_task *utask;

#endif

#if defined(CONFIG_BCACHE) || defined(CONFIG_BCACHE_MODULE)

unsigned intsequential_io;

unsigned intsequential_io_avg;

#endif

};