进程是处于执行期的程序以及它所管理的资源(如打开的文件、挂起的讯号、进程状态、地址空间等等)的合称。注意,程序并不是进程,实际上两个或多个进程除了有可能执行同一程序,并且还有可能共享地址空间等资源。
Linux内核通过一个被称为进程描述符的task_struct结构体来管理进程,这个结构体包含了一个进程所需的所有信息。它定义在include/linux/sched.h文件中。提到task_struct结构体,可以说她是linux内核源码中最复杂的一个结构体了,成员之多,占用显存之大。
嵌入式进阶教程分门别类整理好了linux内核源代码情景分析(下册),看的时侯非常便捷,因为内容较多,这儿就截取一部份图吧。
须要的同事私信【内核】即可申领。
鉴于她的复杂,我们不能简单地玷污,而是要深入“窥探”。下边来渐渐介绍这种复杂成员:
进程状态
volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
state成员的可能取值如下:
/*
* Task state bitmask. NOTE! These bits are also
* encoded in fs/proc/array.c: get_task_state().
*
* We have two separate sets of flags: task->state
* is about runnability, while task->exit_state are
* about the task exiting. Confusing, but this way
* modifying one set can't modify the other one by
* mistake.
*/
#define TASK_RUNNING 0
#define TASK_INTERRUPTIBLE 1
#define TASK_UNINTERRUPTIBLE 2
#define __TASK_STOPPED 4
#define __TASK_TRACED 8
/* in tsk->exit_state */
#define EXIT_DEAD 16
#define EXIT_ZOMBIE 32
#define EXIT_TRACE (EXIT_ZOMBIE | EXIT_DEAD)
/* in tsk->state again */
#define TASK_DEAD 64
#define TASK_WAKEKILL 128 /** wake on signals that are deadly **/
#define TASK_WAKING 256
#define TASK_PARKED 512
#define TASK_NOLOAD 1024
#define TASK_STATE_MAX 2048
/* Convenience macros for the sake of set_task_state */
#define TASK_KILLABLE (TASK_WAKEKILL | TASK_UNINTERRUPTIBLE)
#define TASK_STOPPED (TASK_WAKEKILL | __TASK_STOPPED)
#define TASK_TRACED (TASK_WAKEKILL | __TASK_TRACED)
5个互斥状态
state域才能取5个互为抵触的值(浅显一点就是这五个值任意两个不能一起使用,只能单独使用)。系统中的每位进程都必然处于以上所列进程状态中的一种。
个中止状态
虽然还有两个附加的进程状态既可以被添加到state域中,又可以被添加到exit_state域中。只有当进程中止的时侯,才能达到这两种状态:
/* task state */
int exit_state;
int exit_code, exit_signal;
新增睡眠状态
进程状态TASK_UNINTERRUPTIBLE和TASK_INTERRUPTIBLE都是睡眠状态。如今,我们来瞧瞧内核怎样将进程置为睡眠状态。
内核怎样将进程置为睡眠状态
Linux内核提供了两种方式将进程设置为睡眠状态。
将进程设置为睡眠状态的普通方式是将进程状态设置为TASK_INTERRUPTIBLE或TASK_UNINTERRUPTIBLE并调用调度程序的schedule()函数。这样会将进程从CPU运行队列中移除。
当处于可中断睡眠模式的任务接收到讯号时,它须要处理该讯号(除非它已被屏蔽),离开之前正在处理的任务(此处须要清理代码),并将-EINTR返回给用户空间。再一次,检测这种返回代码和采取适当操作的工作将由程序员完成。
为此,懒惰的程序员可能比较喜欢将进程置为不可中断模式的睡眠状态,由于讯号不会唤起这类任务。
但须要注意的一种情况是,对不可中断睡眠模式的进程的唤起呼叫可能会因为个别诱因不会发生linux内核源代码情景分析(下册),这会使进程难以被中止,因而最终引起问题,由于唯一的解决方式就是重启系统。一方面,您须要考虑一些细节,由于这样做会在内核端和用户端引入bug。另一方面,您可能会生成永远不会停止的进程(被阻塞且难以中止的进程)。
如今,我们在内核中实现了一种新的睡眠方式;LinuxKernel2.6.25引入了一种新的进程睡眠状态:
它定义如下:
#define TASK_WAKEKILL 128 /** wake on signals that are deadly **/
/* Convenience macros for the sake of set_task_state */
#define TASK_KILLABLE (TASK_WAKEKILL | TASK_UNINTERRUPTIBLE)
#define TASK_STOPPED (TASK_WAKEKILL | __TASK_STOPPED)
#define TASK_TRACED (TASK_WAKEKILL | __TASK_TRACED)
换句话说,TASK_UNINTERRUPTIBLE+TASK_WAKEKILL=TASK_KILLABLE。而TASK_WAKEKILL用于在接收到致命讯号时唤起进程;新的睡眠状态容许TASK_UNINTERRUPTIBLE响应致命讯号。进程状态的切换过程和缘由大致如右图:
进程标示符(PID)
pid_t pid;
pid_t tgid;
Unix系统通过pid来标示进程,linux把不同的pid与系统中每位进程或轻量级线程关联,而unix程序员希望同一组线程具有共同的pid,依照这个标准linux引入线程组的概念。一个线程组所有线程与领头线程具有相同的pid,存入tgid数组,getpid()返回当前进程的tgid值而不是pid的值。
在CONFIG_BASE_SMALL配置为0的情况下,PID的取值范围是0到32767,即系统中的进程数最大为32768个。
#define PID_MAX_DEFAULT (CONFIG_BASE_SMALL ? 0x1000 : 0x8000)
在Linux系统中,一个线程组中的所有线程使用和该线程组的领头线程(该组中的第一个轻量级进程)相同的PID,并被储存在tgid成员中。只有线程组的领头线程的pid成员就会被设置为与tgid相同的值。注意,getpid()系统调用返回的是当前进程的tgid值而不是pid值。
进程内核栈
void *stack;
内核栈与线程描述符
对每位进程,Linux内核都把两个不同的数据结构紧凑的储存在一个单独为进程分配的显存区域中
Linux把thread_info(线程描述符)和内核态的线程堆栈储存在一起,这块区域一般是8192K(占两个页框),虽然地址必须是8192的整数倍。
在linux/arch/x86/include/asm/page_32_types.h中,
#define THREAD_SIZE_ORDER 1
#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)
出于效率考虑linux操作系统版本,内核让这8K空间抢占连续的两个页框并让第一个页框的起始地址是213的倍数。
内核态的进程访问处于内核数据段的栈,这个栈不同于用户态的进程所用的栈。
用户态进程所用的栈,是在进程线性地址空间中;而内核栈是当进程从用户空间步入内核空间时,特权能发生变化,须要切换堆栈,这么内核空间中使用的就是这个内核栈。由于内核控制路径使用极少的栈空间,所以只须要几千个字节的内核态堆栈。
须要注意的是,内核态堆栈仅用于内核解释器,Linux内核另外为中断提供了单独的硬中断栈和软中断栈。右图中显示了在数学显存中储存两种数据结构的形式。线程描述符留驻与这个显存区的开始,而栈顶末端向上下降。
右图摘自ULK3,进程内核栈与进程描述符的关系如右图:
而且较新的内核代码中,进程描述符task_struct结构中没有直接指向thread_info结构的表针,而是用一个void表针类型的成员表示,之后通过类型转换来访问thread_info结构。
相关代码在include/linux/sched.h中
#define task_thread_info(task) ((struct thread_info *)(task)->stack)
在这个图中,esp寄存器是CPU栈表针,拿来储存栈顶单元的地址。在80x86系统中,栈起始于顶端,并朝着这个显存区开始的方向下降。从用户态刚切换到内核态之后,进程的内核栈总是空的。为此,esp寄存器指向这个栈的顶端。一旦数据写入堆栈,esp的值就递减。
内核栈数据结构描述thread_info和thread_union
thread_info是体系结构相关的,结构的定义在thread_info.h中
Linux内核中使用一个联合体来表示一个进程的线程描述符和内核栈:
union thread_union
{
struct thread_info thread_info;
unsigned long stack[THREAD_SIZE/sizeof(long)];
};
获取当前在CPU上正在运行进程的thread_info;下边来谈谈怎样通过esp栈表针来获取当前在CPU上正在运行进程的thread_info结构。
实际上,里面提及,thread_info结构和内核态堆栈是紧密结合在一起的,抢占两个页框的数学显存空间。并且,这两个页框的起始起始地址是213对齐的。
初期的版本中,不须要对64位处理器的支持,所以,内核通过简单的屏蔽掉esp的低13位有效位就可以获得thread_info结构的基地址了。
我们在下边对比了,获取正在运行的进程的thread_info的实现方法:
初期版本:当前的栈表针(current_stack_pointer==sp)就是esp,THREAD_SIZE为8K,二补码的表示为0000000000。~(THREAD_SIZE-1)的结果正好为1100000000,第十三位是全为零,也就是恰好屏蔽了esp的低十三位,最终得到的是thread_info的地址。
进程最常用的是进程描述符结构task_struct而不是thread_info结构的地址。为了获取当前CPU上运行进程的task_struct结构,内核提供了current宏,因为task_struct*task在thread_info的起始位置,该宏本质上等价于current_thread_info()->task,在
include/asm-generic/current.h中定义:
#define get_current() (current_thread_info()->task)
#define current get_current()
这个定义是体系结构无关的,其实linux也为各个体系结构定义了愈加便捷或则快速的current
分配和销毁thread_info
进程通过alloc_thread_info_node函数分配它的内核栈,通过free_thread_info函数释放所分配的内核栈。
# if THREAD_SIZE >= PAGE_SIZE
static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
int node)
{
struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP,
THREAD_SIZE_ORDER);
return page ? page_address(page) : NULL;
}
static inline void free_thread_info(struct thread_info *ti)
{
free_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
}
# else
static struct kmem_cache *thread_info_cache;
static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
int node)
{
return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
}
static void free_thread_info(struct thread_info *ti)
{
kmem_cache_free(thread_info_cache, ti);
}
其中,THREAD_SIZE_ORDER宏的定义请查看
进程标记
unsigned int flags; /* per process flags, defined below */
反应进程状态的信息,但不是运行状态,用于内核辨识进程当前的状态linux下socket编程,以备下一步操作;flags成员的可能取值如下,这种宏以PF(ProcessFlag)开头
比如:
PF_FORKNOEXEC 进程刚创建,但还没执行。
PF_SUPERPRIV 超级用户特权。
PF_DUMPCORE dumped core。
PF_SIGNALED 进程被信号(signal)杀出。
PF_EXITING 进程开始关闭。
/*
* Per process flags
*/
#define PF_EXITING 0x00000004 /* getting shut down */
#define PF_EXITPIDONE 0x00000008 /* pi exit done on shut down */
#define PF_VCPU 0x00000010 /* I'm a virtual CPU */
#define PF_WQ_WORKER 0x00000020 /* I'm a workqueue worker */
#define PF_FORKNOEXEC 0x00000040 /* forked but didn't exec */
#define PF_MCE_PROCESS 0x00000080 /* process policy on mce errors */
#define PF_SUPERPRIV 0x00000100 /* used super-user privileges */
#define PF_DUMPCORE 0x00000200 /* dumped core */
#define PF_SIGNALED 0x00000400 /* killed by a signal */
#define PF_MEMALLOC 0x00000800 /* Allocating memory */
#define PF_NPROC_EXCEEDED 0x00001000 /* set_user noticed that RLIMIT_NPROC was exceeded */
#define PF_USED_MATH 0x00002000 /* if unset the fpu must be initialized before use */
#define PF_USED_ASYNC 0x00004000 /* used async_schedule*(), used by module init */
#define PF_NOFREEZE 0x00008000 /* this thread should not be frozen */
#define PF_FROZEN 0x00010000 /* frozen for system suspend */
#define PF_FSTRANS 0x00020000 /* inside a filesystem transaction */
#define PF_KSWAPD 0x00040000 /* I am kswapd */
#define PF_MEMALLOC_NOIO 0x00080000 /* Allocating memory without IO involved */
#define PF_LESS_THROTTLE 0x00100000 /* Throttle me less: I clean memory */
#define PF_KTHREAD 0x00200000 /* I am a kernel thread */
#define PF_RANDOMIZE 0x00400000 /* randomize virtual address space */
#define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */
#define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_allowed */
#define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */
#define PF_MUTEX_TESTER 0x20000000 /* Thread belongs to the rt mutex tester */
#define PF_FREEZER_SKIP 0x40000000 /* Freezer should not count it as freezable */
#define PF_SUSPEND_TASK 0x80000000 /* this thread called freeze_processes and should not be frozen */
表示进程亲属关系的成员:
/*
* 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 */
在Linux系统中,所有进程之间都有着直接或间接地联系,每位进程都有其父进程,也可能有零个或多个子进程。拥有同一父进程的所有进程具有兄弟关系。
ptrace系统调用
Ptrace提供了一种父进程可以控制子进程运行,并可以检测和改变它的核心image。它主要用于实现断点调试。一个被跟踪的进程运行中,直至发生一个讯号。则进程被终止,但是通知其父进程。在进程终止的状态下,进程的显存空间可以被读写。父进程还可以使子进程继续执行,并选择是否是否忽视造成终止的讯号。
unsigned int ptrace;
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;
unsigned long ptrace_message;
siginfo_t *last_siginfo; /* For ptrace use. */
成员ptrace被设置为0时表示不须要被跟踪,它的可能取值如下:
/*
* Ptrace flags
*
* The owner ship rules for task->ptrace which holds the ptrace
* flags is simple. When a task is running it owns it's task->ptrace
* flags. When the a task is stopped the ptracer owns task->ptrace.
*/
#define PT_SEIZED 0x00010000 /* SEIZE used, enable new behavior */
#define PT_PTRACED 0x00000001
#define PT_DTRACE 0x00000002 /* delayed trace (used on m68k, i386) */
#define PT_PTRACE_CAP 0x00000004 /* ptracer can follow suid-exec */
#define PT_OPT_FLAG_SHIFT 3
/* PT_TRACE_* event enable flags */
#define PT_EVENT_FLAG(event) (1 << (PT_OPT_FLAG_SHIFT + (event)))
#define PT_TRACESYSGOOD PT_EVENT_FLAG(0)
#define PT_TRACE_FORK PT_EVENT_FLAG(PTRACE_EVENT_FORK)
#define PT_TRACE_VFORK PT_EVENT_FLAG(PTRACE_EVENT_VFORK)
#define PT_TRACE_CLONE PT_EVENT_FLAG(PTRACE_EVENT_CLONE)
#define PT_TRACE_EXEC PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
#define PT_TRACE_VFORK_DONE PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
#define PT_TRACE_EXIT PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
#define PT_TRACE_SECCOMP PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
#define PT_EXITKILL (PTRACE_O_EXITKILL << PT_OPT_FLAG_SHIFT)
#define PT_SUSPEND_SECCOMP (PTRACE_O_SUSPEND_SECCOMP << PT_OPT_FLAG_SHIFT)
/* single stepping state bits (used on ARM and PA-RISC) */
#define PT_SINGLESTEP_BIT 31
#define PT_SINGLESTEP (1<<PT_SINGLESTEP_BIT)
#define PT_BLOCKSTEP_BIT 30
#define PT_BLOCKSTEP (1<<PT_BLOCKSTEP_BIT)
Performance Event
Performance Event是一款随 Linux 内核代码一同发布和维护的性能诊断工具。这些成员用于帮助PerformanceEvent分析进程的性能问题。
#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
进程调度
优先级
int prio, static_prio, normal_prio;
unsigned int rt_priority;
实时优先级范围是0到MAX_RT_PRIO-1(即99),而普通进程的静态优先级范围是从MAX_RT_PRIO到MAX_PRIO-1(即100到139)。值越大静态优先级越低。
/* http://lxr.free-electrons.com/source/include/linux/sched/prio.h#L21 */
#define MAX_USER_RT_PRIO 100
#define MAX_RT_PRIO MAX_USER_RT_PRIO
/* http://lxr.free-electrons.com/source/include/linux/sched/prio.h#L24 */
#define MAX_PRIO (MAX_RT_PRIO + 40)
#define DEFAULT_PRIO (MAX_RT_PRIO + 20)
调度策略相关数组
/* http://lxr.free-electrons.com/source/include/linux/sched.h?v=4.5#L1426 */
unsigned int policy;
/* http://lxr.free-electrons.com/source/include/linux/sched.h?v=4.5#L1409 */
const struct sched_class *sched_class;
struct sched_entity se;
struct sched_rt_entity rt;
cpumask_t cpus_allowed;
调度策略
policy表示进程的调度策略,目前主要有以下五种:
/*
* Scheduling policies
*/
#define SCHED_NORMAL 0
#define SCHED_FIFO 1
#define SCHED_RR 2
#define SCHED_BATCH 3
/* SCHED_ISO: reserved but not implemented yet */
#define SCHED_IDLE 5
#define SCHED_DEADLINE 6
调度类
sched_class结构体表示调度类,目前内核中有实现以下四种:
extern const struct sched_class stop_sched_class;
extern const struct sched_class dl_sched_class;
extern const struct sched_class rt_sched_class;
extern const struct sched_class fair_sched_class;
extern const struct sched_class idle_sched_class;
目前系統中,SchedulingClass的优先级次序为StopTask>RealTime>Fair>IdleTask,开发者可以依据己的设计需求,來把所属的Task配置到不同的SchedulingClass中.
进程地址空间
/* http://lxr.free-electrons.com/source/include/linux/sched.h?V=4.5#L1453 */
struct mm_struct *mm, *active_mm;
/* per-thread vma caching */
u32 vmacache_seqnum;
struct vm_area_struct *vmacache[VMACACHE_SIZE];
#if defined(SPLIT_RSS_COUNTING)
struct task_rss_stat rss_stat;
#endif
/* http://lxr.free-electrons.com/source/include/linux/sched.h?V=4.5#L1484 */
#ifdef CONFIG_COMPAT_BRK
unsigned brk_randomized:1;
#endif
因而假如当前内核线程被调度之前运行的也是另外一个内核线程时侯,这么其mm和avtive_mm都是NULL
判定标志
int exit_code, exit_signal;
int pdeath_signal; /* The signal sent when the parent dies */
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;
时间
cputime_t utime, stime, utimescaled, stimescaled;
cputime_t gtime;
struct prev_cputime prev_cputime;
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
seqcount_t vtime_seqcount;
unsigned long long vtime_snap;
enum {
/* Task is sleeping or running in a CPU with VTIME inactive */
VTIME_INACTIVE = 0,
/* Task runs in userspace in a CPU with VTIME active */
VTIME_USER,
/* Task runs in kernelspace in a CPU with VTIME active */
VTIME_SYS,
} vtime_snap_whence;
#endif
unsigned long nvcsw, nivcsw; /* context switch counts */
u64 start_time; /* monotonic time in nsec */
u64 real_start_time; /* boot based time in nsec */
/* 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 */
struct nameidata *nameidata;
#ifdef CONFIG_SYSVIPC
/* ipc stuff */
struct sysv_sem sysvsem;
struct sysv_shm sysvshm;
#endif
#ifdef CONFIG_DETECT_HUNG_TASK
/* hung task detection */
unsigned long last_switch_count;
#endif
讯号处理
/* signal handlers */
struct signal_struct *signal;
struct sighand_struct *sighand;
1583
sigset_t blocked, real_blocked;
sigset_t saved_sigmask; /* restored if set_restore_sigmask() was used */
struct sigpending pending;
1587
unsigned long sas_ss_sp;
size_t sas_ss_size;
其他
(1)、用于保护资源分配或释放的载流子锁
/* Protection of (de-)allocation: mm, files, fs, tty, keyrings, mems_allowed,
* mempolicy */
spinlock_t alloc_lock;
(2)、进程描述符使用计数,被置为2时,表示进程描述符正在被使用并且其相应的进程处于活动状态
atomic_t usage;
(3)、用于表示获取大内核锁的次数,假如进程未获得过锁,则置为-1。
int lock_depth; /* BKL lock depth */
(4)、在SMP上帮助实现无加锁的进程切换(unlockedcontextswitches)
#ifdef CONFIG_SMP
#ifdef __ARCH_WANT_UNLOCKED_CTXSW
int oncpu;
#endif
#endif
(5)、preempt_notifier结构体数组
#ifdef CONFIG_PREEMPT_NOTIFIERS
/* list of struct preempt_notifier: */
struct hlist_head preempt_notifiers;
#endif
(6)、FPU使用计数
unsigned char fpu_counter;
(7)、blktrace是一个针对Linux内核中块设备I/O层的跟踪工具。
#ifdef CONFIG_BLK_DEV_IO_TRACE
unsigned int btrace_seq;
#endif
(8)、RCU同步谓词
#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 */
(9)、用于调度器统计进程的运行信息
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
struct sched_info sched_info;
#endif
(10)、用于建立进程数组
struct list_head tasks;
(11)、tolimitpushingtooneattempt
#ifdef CONFIG_SMP
struct plist_node pushable_tasks;
#endif
(12)、防止内核堆栈溢出
#ifdef CONFIG_CC_STACKPROTECTOR
/* Canary value for the -fstack-protector gcc feature */
unsigned long stack_canary;
#endif
在GCC编译内核时,须要加上-fstack-protector选项。
(13)、PID散列表和数组
/* PID/PID hash table linkage. */
struct pid_link pids[PIDTYPE_MAX];
struct list_head thread_group; //线程组中所有进程的链表
(14)、do_fork函数
struct completion *vfork_done; /* for vfork() */
int __user *set_child_tid; /* CLONE_CHILD_SETTID */
int __user *clear_child_tid; /* CLONE_CHILD_CLEARTID */
在执行do_fork()时,假若给定非常标志,则vfork_done会指向一个特殊地址。
假如copy_process函数的clone_flags参数的值被置为CLONE_CHILD_SETTID或CLONE_CHILD_CLEARTID,则会把child_tidptr参数的值分别复制到set_child_tid和clear_child_tid成员。这种标志说明必须改变子进程用户态地址空间的child_tidptr所指向的变量的值。
(15)、缺页统计
/* mm fault and swap info: this can arguably be seen as either mm-specific or thread-specific */
unsigned long min_flt, maj_flt;
(16)、进程权能
const struct cred __rcu *real_cred; /* objective and real subjective task
* credentials (COW) */
const struct cred __rcu *cred; /* effective (overridable) subjective task
* credentials (COW) */
struct cred *replacement_session_keyring; /* for KEYCTL_SESSION_TO_PARENT */
(17)、相应的程序名
char comm[TASK_COMM_LEN];
(18)、文件
/* file system info */
int link_count, total_link_count;
/* filesystem information */
struct fs_struct *fs;
/* open file information */
struct files_struct *files;
fs拿来表示进程与文件系统的联系,包括当前目录和根目录。
files表示进程当前打开的文件。
(19)、进程通讯(SYSVIPC)
#ifdef CONFIG_SYSVIPC
/* ipc stuff */
struct sysv_sem sysvsem;
#endif
(20)、处理器特有数据
/* CPU-specific state of this task */
struct thread_struct thread;
(21)、命名空间
/* namespaces */
struct nsproxy *nsproxy;
(22)、进程审计
struct audit_context *audit_context;
#ifdef CONFIG_AUDITSYSCALL
uid_t loginuid;
unsigned int sessionid;
#endif
(23)、securecomputing
seccomp_t seccomp;
(24)、用于copy_process函数使用CLONE_PARENT标记时
/* Thread group tracking */
u32 parent_exec_id;
u32 self_exec_id;
(25)、中断
#ifdef CONFIG_GENERIC_HARDIRQS
/* IRQ handler threads */
struct irqaction *irqaction;
#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
(26)、task_rq_lock函数所使用的锁
/* Protection of the PI data structures: */
raw_spinlock_t pi_lock;
(27)、基于PI合同的等待互斥锁,其中PI指的是priorityinheritance(优先级承继)
#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
(28)、死锁检查
#ifdef CONFIG_DEBUG_MUTEXES
/* mutex deadlock detection */
struct mutex_waiter *blocked_on;
#endif
(29)、JFS文件系统
/* journalling filesystem info */
void *journal_info;
(30)、块设备数组
/* stacked block device info */
struct bio_list *bio_list;
(31)、内存回收
struct reclaim_state *reclaim_state;
(32)、存放块设备I/O数据流量信息
struct backing_dev_info *backing_dev_info;
(33)、I/O调度器所使用的信息
struct io_context *io_context;
(34)、记录进程的I/O计数
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
在Ubuntu11.04上,执行cat获得进程1的I/O计数如下:
输出的数据项正好是task_io_accounting结构体的所有成员。
(35)、CPUSET功能
#ifdef CONFIG_CPUSETS
nodemask_t mems_allowed; /* Protected by alloc_lock */
int mems_allowed_change_disable;
int cpuset_mem_spread_rotor;
int cpuset_slab_spread_rotor;
#endif
(36)、ControlGroups
#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_CGROUP_MEM_RES_CTLR /* 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 bytes; /* uncharged usage */
unsigned long memsw_bytes; /* uncharged mem+swap usage */
} memcg_batch;
#endif
(37)、futex同步机制
#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
(38)、非一致显存访问(NUMANon-UniformMemoryAccess)
#ifdef CONFIG_NUMA
struct mempolicy *mempolicy; /* Protected by alloc_lock */
short il_next;
#endif
(39)、文件系统互注资源
atomic_t fs_excl; /* holding fs exclusive resources */
(40)、RCU数组
struct rcu_head rcu;
(41)、管道
struct pipe_inode_info *splice_pipe;
(42)、延迟计数
#ifdef CONFIG_TASK_DELAY_ACCT
struct task_delay_info *delays;
#endif
(43)、faultinjection
#ifdef CONFIG_FAULT_INJECTION
int make_it_fail;
#endif
(44)、FLoatingproportions
struct prop_local_single dirties;
(45)、Infrastructurefordisplayinglatency
#ifdef CONFIG_LATENCYTOP
int latency_record_count;
struct latency_record latency_record[LT_SAVECOUNT];
#endif
(46)、timeslackvalues,常用于poll和select函数
unsigned long timer_slack_ns;
unsigned long default_timer_slack_ns;
(48)、socket控制消息(controlmessage)
struct list_head *scm_work_list;
(47)、ftrace跟踪器
#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 of trace recursion */
unsigned long trace_recursion;
#endif /* CONFIG_TRACING */