cd /
find -name sched.h
vim usr/src/kernels/3.10.0862.6.3.el7.x86_64/include/linux/sched.h
https://www.cnblogs.com/zxc2man/p/6649771.html
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、挂起的信号、进程状态、地址空间等等）的总称。注意，程序并不是进程，实际上两个或多个进程不仅有可能执行同一程序，而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linux-2.6.38.8/include/linux/sched.h文件中。
本文将尽力就task_struct结构体所有成员的用法进行简要说明。
1、进程状态
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volatile long state;
int exit_state;
volatile long state;
int exit_state;
state成员的可能取值如下：
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#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_ZOMBIE 16
#define EXIT_DEAD 32
/ in tsk->state again /
#define TASK_DEAD 64
#define TASK_WAKEKILL 128
#define TASK_WAKING 256
#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_ZOMBIE 16
#define EXIT_DEAD 32
/ in tsk->state again */
#define TASK_DEAD 64
#define TASK_WAKEKILL 128
#define TASK_WAKING 256
系统中的每个进程都必然处于以上所列进程状态中的一种。
TASK_RUNNING表示进程要么正在执行，要么正要准备执行。
TASK_INTERRUPTIBLE表示进程被阻塞（睡眠），直到某个条件变为真。条件一旦达成，进程的状态就被设置为TASK_RUNNING。
TASK_UNINTERRUPTIBLE的意义与TASK_INTERRUPTIBLE类似，除了不能通过接受一个信号来唤醒以外。
__TASK_STOPPED表示进程被停止执行。
__TASK_TRACED表示进程被debugger等进程监视。
EXIT_ZOMBIE表示进程的执行被终止，但是其父进程还没有使用wait()等系统调用来获知它的终止信息。
EXIT_DEAD表示进程的最终状态。
EXIT_ZOMBIE和EXIT_DEAD也可以存放在exit_state成员中。进程状态的切换过程和原因大致如下图（图片来自《Linux Kernel Development》）：
2、进程标识符（PID）
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pid_t pid;
pid_t tgid;
pid_t pid;
pid_t tgid;
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。
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/* linux-2.6.38.8/include/linux/threads.h */
#define PID_MAX_DEFAULT (CONFIG_BASE_SMALL ? 0x1000 : 0x8000)
/* linux-2.6.38.8/include/linux/threads.h */
#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，并被存放在tgid成员中。只有线程组的领头线程的pid成员才会被设置为与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。
3、进程内核栈
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void *stack;
void *stack;
进程通过alloc_thread_info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。
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/* linux-2.6.38.8/kernel/fork.c */
static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
{
#ifdef CONFIG_DEBUG_STACK_USAGE
gfp_t mask = GFP_KERNEL | __GFP_ZERO;
#else
gfp_t mask = GFP_KERNEL;
#endif
return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
}
static inline void free_thread_info(struct thread_info *ti)
{
free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
}
/* linux-2.6.38.8/kernel/fork.c */
static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
{
#ifdef CONFIG_DEBUG_STACK_USAGE
gfp_t mask = GFP_KERNEL | __GFP_ZERO;
#else
gfp_t mask = GFP_KERNEL;
#endif
return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
}
static inline void free_thread_info(struct thread_info *ti)
{
free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
}
其中，THREAD_SIZE_ORDER宏在linux-2.6.38.8/arch/arm/include/asm/thread_info.h文件中被定义为1，也就是说alloc_thread_info函数通过调用__get_free_pages函数分配2个页的内存（它的首地址是8192字节对齐的）。
Linux内核通过thread_union联合体来表示进程的内核栈，其中THREAD_SIZE宏的大小为8192。
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union thread_union {
struct thread_info thread_info;
unsigned long stack[THREAD_SIZE/sizeof(long)];
};
union thread_union {
struct thread_info thread_info;
unsigned long stack[THREAD_SIZE/sizeof(long)];
};
当进程从用户态切换到内核态时，进程的内核栈总是空的，所以ARM的sp寄存器指向这个栈的顶端。因此，内核能够轻易地通过sp寄存器获得当前正在CPU上运行的进程。
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/* linux-2.6.38.8/arch/arm/include/asm/current.h */
static inline struct task_struct *get_current(void)
{
return current_thread_info()->task;
}
#define current (get_current())
/* linux-2.6.38.8/arch/arm/include/asm/thread_info.h */
static inline struct thread_info *current_thread_info(void)
{
register unsigned long sp asm (“sp”);
return (struct thread_info )(sp & ~(THREAD_SIZE - 1));
}
/ linux-2.6.38.8/arch/arm/include/asm/current.h */
static inline struct task_struct *get_current(void)
{
return current_thread_info()->task;
}
#define current (get_current())
/* linux-2.6.38.8/arch/arm/include/asm/thread_info.h */
static inline struct thread_info *current_thread_info(void)
{
register unsigned long sp asm (“sp”);
return (struct thread_info *)(sp & ~(THREAD_SIZE - 1));
}
进程内核栈与进程描述符的关系如下图：
4、标记
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unsigned int flags; /* per process flags, defined below */
unsigned int flags; /* per process flags, defined below */
flags成员的可能取值如下：
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#define PF_KSOFTIRQD 0x00000001 /* I am ksoftirqd /
#define PF_STARTING 0x00000002 / being created /
#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_USED_MATH 0x00002000 / if unset the fpu must be initialized before use /
#define PF_FREEZING 0x00004000 / freeze in progress. do not account to load /
#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_OOM_ORIGIN 0x00080000 / Allocating much memory to others /
#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_SPREAD_PAGE 0x01000000 / Spread page cache over cpuset /
#define PF_SPREAD_SLAB 0x02000000 / Spread some slab caches over cpuset /
#define PF_THREAD_BOUND 0x04000000 / Thread bound to specific cpu /
#define PF_MCE_EARLY 0x08000000 / Early kill for mce process policy /
#define PF_MEMPOLICY 0x10000000 / Non-default NUMA mempolicy /
#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_FREEZER_NOSIG 0x80000000 / Freezer won’t send signals to it /
#define PF_KSOFTIRQD 0x00000001 / I am ksoftirqd /
#define PF_STARTING 0x00000002 / being created /
#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_USED_MATH 0x00002000 / if unset the fpu must be initialized before use /
#define PF_FREEZING 0x00004000 / freeze in progress. do not account to load /
#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_OOM_ORIGIN 0x00080000 / Allocating much memory to others /
#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_SPREAD_PAGE 0x01000000 / Spread page cache over cpuset /
#define PF_SPREAD_SLAB 0x02000000 / Spread some slab caches over cpuset /
#define PF_THREAD_BOUND 0x04000000 / Thread bound to specific cpu /
#define PF_MCE_EARLY 0x08000000 / Early kill for mce process policy /
#define PF_MEMPOLICY 0x10000000 / Non-default NUMA mempolicy /
#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_FREEZER_NOSIG 0x80000000 / Freezer won’t send signals to it */
5、表示进程亲属关系的成员
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struct task_struct real_parent; / real parent process */
struct task_struct parent; / recipient of SIGCHLD, wait4() reports /
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 task_struct real_parent; / real parent process */
struct task_struct parent; / recipient of SIGCHLD, wait4() reports /
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，每个进程都有其父进程，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。
real_parent指向其父进程，如果创建它的父进程不再存在，则指向PID为1的init进程。
parent指向其父进程，当它终止时，必须向它的父进程发送信号。它的值通常与real_parent相同。
children表示链表的头部，链表中的所有元素都是它的子进程。
sibling用于把当前进程插入到兄弟链表中。
group_leader指向其所在进程组的领头进程。
6、ptrace系统调用
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unsigned int ptrace;
struct list_head ptraced;
struct list_head ptrace_entry;
unsigned long ptrace_message;
siginfo_t last_siginfo; / For ptrace use. */
ifdef CONFIG_HAVE_HW_BREAKPOINT
atomic_t ptrace_bp_refcnt;
endif
unsigned int ptrace;
struct list_head ptraced;
struct list_head ptrace_entry;
unsigned long ptrace_message;
siginfo_t *last_siginfo; /* For ptrace use. */
#ifdef CONFIG_HAVE_HW_BREAKPOINT
atomic_t ptrace_bp_refcnt;
#endif
成员ptrace被设置为0时表示不需要被跟踪，它的可能取值如下：
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/* linux-2.6.38.8/include/linux/ptrace.h /
#define PT_PTRACED 0x00000001
#define PT_DTRACE 0x00000002 / delayed trace (used on m68k, i386) /
#define PT_TRACESYSGOOD 0x00000004
#define PT_PTRACE_CAP 0x00000008 / ptracer can follow suid-exec */
#define PT_TRACE_FORK 0x00000010
#define PT_TRACE_VFORK 0x00000020
#define PT_TRACE_CLONE 0x00000040
#define PT_TRACE_EXEC 0x00000080
#define PT_TRACE_VFORK_DONE 0x00000100
#define PT_TRACE_EXIT 0x00000200
/* linux-2.6.38.8/include/linux/ptrace.h /
#define PT_PTRACED 0x00000001
#define PT_DTRACE 0x00000002 / delayed trace (used on m68k, i386) /
#define PT_TRACESYSGOOD 0x00000004
#define PT_PTRACE_CAP 0x00000008 / ptracer can follow suid-exec */
#define PT_TRACE_FORK 0x00000010
#define PT_TRACE_VFORK 0x00000020
#define PT_TRACE_CLONE 0x00000040
#define PT_TRACE_EXEC 0x00000080
#define PT_TRACE_VFORK_DONE 0x00000100
#define PT_TRACE_EXIT 0x00000200
7、Performance Event
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#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_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
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。
关于Performance Event工具的介绍可参考文章http://www.ibm.com/developerworks/cn/linux/l-cn-perf1/index.html?ca=drs-#major1和http://www.ibm.com/developerworks/cn/linux/l-cn-perf2/index.html?ca=drs-#major1。
8、进程调度
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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;
unsigned int policy;
cpumask_t cpus_allowed;
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;
unsigned int policy;
cpumask_t cpus_allowed;
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。
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/* linux-2.6.38.8/include/linux/sched.h */
#define MAX_USER_RT_PRIO 100
#define MAX_RT_PRIO MAX_USER_RT_PRIO
#define MAX_PRIO (MAX_RT_PRIO + 40)
#define DEFAULT_PRIO (MAX_RT_PRIO + 20)
/* linux-2.6.38.8/include/linux/sched.h */
#define MAX_USER_RT_PRIO 100
#define MAX_RT_PRIO MAX_USER_RT_PRIO
#define MAX_PRIO (MAX_RT_PRIO + 40)
#define DEFAULT_PRIO (MAX_RT_PRIO + 20)
static_prio用于保存静态优先级，可以通过nice系统调用来进行修改。
rt_priority用于保存实时优先级。
normal_prio的值取决于静态优先级和调度策略。
prio用于保存动态优先级。
policy表示进程的调度策略，目前主要有以下五种：
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#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_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
SCHED_NORMAL用于普通进程，通过CFS调度器实现。SCHED_BATCH用于非交互的处理器消耗型进程。SCHED_IDLE是在系统负载很低时使用。
SCHED_FIFO（先入先出调度算法）和SCHED_RR（轮流调度算法）都是实时调度策略。
sched_class结构体表示调度类，目前内核中有实现以下四种：
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/* linux-2.6.38.8/kernel/sched_fair.c /
static const struct sched_class fair_sched_class;
/ linux-2.6.38.8/kernel/sched_rt.c /
static const struct sched_class rt_sched_class;
/ linux-2.6.38.8/kernel/sched_idletask.c /
static const struct sched_class idle_sched_class;
/ linux-2.6.38.8/kernel/sched_stoptask.c */
static const struct sched_class stop_sched_class;
/* linux-2.6.38.8/kernel/sched_fair.c /
static const struct sched_class fair_sched_class;
/ linux-2.6.38.8/kernel/sched_rt.c /
static const struct sched_class rt_sched_class;
/ linux-2.6.38.8/kernel/sched_idletask.c /
static const struct sched_class idle_sched_class;
/ linux-2.6.38.8/kernel/sched_stoptask.c */
static const struct sched_class stop_sched_class;
se和rt都是调用实体，一个用于普通进程，一个用于实时进程，每个进程都有其中之一的实体。
cpus_allowed用于控制进程可以在哪里处理器上运行。
9、进程地址空间
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struct mm_struct *mm, *active_mm;
#ifdef CONFIG_COMPAT_BRK
unsigned brk_randomized:1;
#endif
#if defined(SPLIT_RSS_COUNTING)
struct task_rss_stat rss_stat;
#endif
struct mm_struct *mm, *active_mm;
#ifdef CONFIG_COMPAT_BRK
unsigned brk_randomized:1;
#endif
#if defined(SPLIT_RSS_COUNTING)
struct task_rss_stat rss_stat;
#endif
mm指向进程所拥有的内存描述符，而active_mm指向进程运行时所使用的内存描述符。对于普通进程而言，这两个指针变量的值相同。但是，内核线程不拥有任何内存描述符，所以它们的mm成员总是为NULL。当内核线程得以运行时，它的active_mm成员被初始化为前一个运行进程的active_mm值。
brk_randomized的用法在http://lkml.indiana.edu/hypermail/Linux/kernel/1104.1/00196.html上有介绍，用来确定对随机堆内存的探测。
rss_stat用来记录缓冲信息。
10、判断标志
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int exit_code, exit_signal;
int pdeath_signal; /* The signal sent when the parent dies /
/ ??? /
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;
/* Revert to default priority/policy when forking /
unsigned sched_reset_on_fork:1;
int exit_code, exit_signal;
int pdeath_signal; / The signal sent when the parent dies /
/ ??? /
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;
/* Revert to default priority/policy when forking */
unsigned sched_reset_on_fork:1;
exit_code用于设置进程的终止代号，这个值要么是_exit()或exit_group()系统调用参数（正常终止），要么是由内核提供的一个错误代号（异常终止）。
exit_signal被置为-1时表示是某个线程组中的一员。只有当线程组的最后一个成员终止时，才会产生一个信号，以通知线程组的领头进程的父进程。
pdeath_signal用于判断父进程终止时发送信号。
personality用于处理不同的ABI，它的可能取值如下：
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enum {
PER_LINUX = 0x0000,
PER_LINUX_32BIT = 0x0000 | ADDR_LIMIT_32BIT,
PER_LINUX_FDPIC = 0x0000 | FDPIC_FUNCPTRS,
PER_SVR4 = 0x0001 | STICKY_TIMEOUTS | MMAP_PAGE_ZERO,
PER_SVR3 = 0x0002 | STICKY_TIMEOUTS | SHORT_INODE,
PER_SCOSVR3 = 0x0003 | STICKY_TIMEOUTS |
WHOLE_SECONDS | SHORT_INODE,
PER_OSR5 = 0x0003 | STICKY_TIMEOUTS | WHOLE_SECONDS,
PER_WYSEV386 = 0x0004 | STICKY_TIMEOUTS | SHORT_INODE,
PER_ISCR4 = 0x0005 | STICKY_TIMEOUTS,
PER_BSD = 0x0006,
PER_SUNOS = 0x0006 | STICKY_TIMEOUTS,
PER_XENIX = 0x0007 | STICKY_TIMEOUTS | SHORT_INODE,
PER_LINUX32 = 0x0008,
PER_LINUX32_3GB = 0x0008 | ADDR_LIMIT_3GB,
PER_IRIX32 = 0x0009 | STICKY_TIMEOUTS,/* IRIX5 32-bit /
PER_IRIXN32 = 0x000a | STICKY_TIMEOUTS,/ IRIX6 new 32-bit /
PER_IRIX64 = 0x000b | STICKY_TIMEOUTS,/ IRIX6 64-bit /
PER_RISCOS = 0x000c,
PER_SOLARIS = 0x000d | STICKY_TIMEOUTS,
PER_UW7 = 0x000e | STICKY_TIMEOUTS | MMAP_PAGE_ZERO,
PER_OSF4 = 0x000f, / OSF/1 v4 /
PER_HPUX = 0x0010,
PER_MASK = 0x00ff,
};
enum {
PER_LINUX = 0x0000,
PER_LINUX_32BIT = 0x0000 | ADDR_LIMIT_32BIT,
PER_LINUX_FDPIC = 0x0000 | FDPIC_FUNCPTRS,
PER_SVR4 = 0x0001 | STICKY_TIMEOUTS | MMAP_PAGE_ZERO,
PER_SVR3 = 0x0002 | STICKY_TIMEOUTS | SHORT_INODE,
PER_SCOSVR3 = 0x0003 | STICKY_TIMEOUTS |
WHOLE_SECONDS | SHORT_INODE,
PER_OSR5 = 0x0003 | STICKY_TIMEOUTS | WHOLE_SECONDS,
PER_WYSEV386 = 0x0004 | STICKY_TIMEOUTS | SHORT_INODE,
PER_ISCR4 = 0x0005 | STICKY_TIMEOUTS,
PER_BSD = 0x0006,
PER_SUNOS = 0x0006 | STICKY_TIMEOUTS,
PER_XENIX = 0x0007 | STICKY_TIMEOUTS | SHORT_INODE,
PER_LINUX32 = 0x0008,
PER_LINUX32_3GB = 0x0008 | ADDR_LIMIT_3GB,
PER_IRIX32 = 0x0009 | STICKY_TIMEOUTS,/ IRIX5 32-bit /
PER_IRIXN32 = 0x000a | STICKY_TIMEOUTS,/ IRIX6 new 32-bit /
PER_IRIX64 = 0x000b | STICKY_TIMEOUTS,/ IRIX6 64-bit /
PER_RISCOS = 0x000c,
PER_SOLARIS = 0x000d | STICKY_TIMEOUTS,
PER_UW7 = 0x000e | STICKY_TIMEOUTS | MMAP_PAGE_ZERO,
PER_OSF4 = 0x000f, / OSF/1 v4 */
PER_HPUX = 0x0010,
PER_MASK = 0x00ff,
};
did_exec用于记录进程代码是否被execve()函数所执行。
in_execve用于通知LSM是否被do_execve()函数所调用。详见补丁说明：http://lkml.indiana.edu/hypermail/linux/kernel/0901.1/00014.html。
in_iowait用于判断是否进行iowait计数。
sched_reset_on_fork用于判断是否恢复默认的优先级或调度策略。
11、时间
[cpp] view plain copy print?
cputime_t utime, stime, utimescaled, stimescaled;
cputime_t gtime;
#ifndef CONFIG_VIRT_CPU_ACCOUNTING
cputime_t prev_utime, prev_stime;
#endif
unsigned long nvcsw, nivcsw; /* context switch counts /
struct timespec start_time; / monotonic time /
struct timespec real_start_time; / boot based time /
struct task_cputime cputime_expires;
struct list_head cpu_timers[3];
#ifdef CONFIG_DETECT_HUNG_TASK
/ hung task detection /
unsigned long last_switch_count;
#endif
cputime_t utime, stime, utimescaled, stimescaled;
cputime_t gtime;
#ifndef CONFIG_VIRT_CPU_ACCOUNTING
cputime_t prev_utime, prev_stime;
#endif
unsigned long nvcsw, nivcsw; / context switch counts /
struct timespec start_time; / monotonic time /
struct timespec real_start_time; / boot based time /
struct task_cputime cputime_expires;
struct list_head cpu_timers[3];
#ifdef CONFIG_DETECT_HUNG_TASK
/ hung task detection */
unsigned long last_switch_count;
#endif
utime/stime用于记录进程在用户态/内核态下所经过的节拍数（定时器）。prev_utime/prev_stime是先前的运行时间，请参考补丁说明http://lkml.indiana.edu/hypermail/linux/kernel/1003.3/02431.html。
utimescaled/stimescaled也是用于记录进程在用户态/内核态的运行时间，但它们以处理器的频率为刻度。
gtime是以节拍计数的虚拟机运行时间（guest time）。
nvcsw/nivcsw是自愿（voluntary）/非自愿（involuntary）上下文切换计数。last_switch_count是nvcsw和nivcsw的总和。
start_time和real_start_time都是进程创建时间，real_start_time还包含了进程睡眠时间，常用于/proc/pid/stat，补丁说明请参考http://lkml.indiana.edu/hypermail/linux/kernel/0705.0/2094.html。
cputime_expires用来统计进程或进程组被跟踪的处理器时间，其中的三个成员对应着cpu_timers[3]的三个链表。
12、信号处理
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/* 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;
/* 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;
signal指向进程的信号描述符。
sighand指向进程的信号处理程序描述符。
blocked表示被阻塞信号的掩码，real_blocked表示临时掩码。
pending存放私有挂起信号的数据结构。
sas_ss_sp是信号处理程序备用堆栈的地址，sas_ss_size表示堆栈的大小。
设备驱动程序常用notifier指向的函数来阻塞进程的某些信号（notifier_mask是这些信号的位掩码），notifier_data指的是notifier所指向的函数可能使用的数据。
13、其他
（1）、用于保护资源分配或释放的自旋锁
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/* Protection of (de-)allocation: mm, files, fs, tty, keyrings, mems_allowed,
- mempolicy */
spinlock_t alloc_lock;
/* 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而且其相应的进程处于活动状态。
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atomic_t usage;
atomic_t usage;
（3）、用于表示获取大内核锁的次数，如果进程未获得过锁，则置为-1。
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int lock_depth; /* BKL lock depth */
int lock_depth; /* BKL lock depth */
（4）、在SMP上帮助实现无加锁的进程切换（unlocked context switches）
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#ifdef CONFIG_SMP
#ifdef __ARCH_WANT_UNLOCKED_CTXSW
int oncpu;
#endif
#endif
#ifdef CONFIG_SMP
#ifdef __ARCH_WANT_UNLOCKED_CTXSW
int oncpu;
#endif
#endif
（5）、preempt_notifier结构体链表
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#ifdef CONFIG_PREEMPT_NOTIFIERS
/* list of struct preempt_notifier: */
struct hlist_head preempt_notifiers;
#endif
#ifdef CONFIG_PREEMPT_NOTIFIERS
/* list of struct preempt_notifier: */
struct hlist_head preempt_notifiers;
#endif
（6）、FPU使用计数
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unsigned char fpu_counter;
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。
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#ifdef CONFIG_BLK_DEV_IO_TRACE
unsigned int btrace_seq;
#endif
#ifdef CONFIG_BLK_DEV_IO_TRACE
unsigned int btrace_seq;
#endif
（8）、RCU同步原语
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#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 */
#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
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#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
struct sched_info sched_info;
#endif
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
struct sched_info sched_info;
#endif
（10）、用于构建进程链表
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struct list_head tasks;
struct list_head tasks;
（11）、to limit pushing to one attempt
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#ifdef CONFIG_SMP
struct plist_node pushable_tasks;
#endif
#ifdef CONFIG_SMP
struct plist_node pushable_tasks;
#endif
补丁说明请参考：http://lkml.indiana.edu/hypermail/linux/kernel/0808.3/0503.html
（12）、防止内核堆栈溢出
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#ifdef CONFIG_CC_STACKPROTECTOR
/* Canary value for the -fstack-protector gcc feature /
unsigned long stack_canary;
#endif
#ifdef CONFIG_CC_STACKPROTECTOR
/ Canary value for the -fstack-protector gcc feature */
unsigned long stack_canary;
#endif
在GCC编译内核时，需要加上-fstack-protector选项。
（13）、PID散列表和链表
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/* 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
/* 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
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struct completion vfork_done; / for vfork() */
int __user set_child_tid; / CLONE_CHILD_SETTID */
int __user clear_child_tid; / CLONE_CHILD_CLEARTID */
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，如果给定特别标志，则vfork_done会指向一个特殊地址。
如果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。这些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
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/* mm fault and swap info: this can arguably be seen as either mm-specific or thread-specific */
unsigned long min_flt, maj_flt;
/* 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
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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 */
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
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char comm[TASK_COMM_LEN];
char comm[TASK_COMM_LEN];
（18）、文件
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/* file system info /
int link_count, total_link_count;
/ filesystem information */
struct fs_struct fs;
/ open file information */
struct files_struct *files;
/* file system info /
int link_count, total_link_count;
/ filesystem information */
struct fs_struct fs;
/ open file information */
struct files_struct *files;
fs用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）、进程通信（SYSVIPC）
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#ifdef CONFIG_SYSVIPC
/* ipc stuff /
struct sysv_sem sysvsem;
#endif
#ifdef CONFIG_SYSVIPC
/ ipc stuff */
struct sysv_sem sysvsem;
#endif
（20）、处理器特有数据
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/* CPU-specific state of this task */
struct thread_struct thread;
/* CPU-specific state of this task */
struct thread_struct thread;
（21）、命名空间
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/* namespaces */
struct nsproxy *nsproxy;
/* namespaces */
struct nsproxy *nsproxy;
（22）、进程审计
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struct audit_context *audit_context;
#ifdef CONFIG_AUDITSYSCALL
uid_t loginuid;
unsigned int sessionid;
#endif
struct audit_context *audit_context;
#ifdef CONFIG_AUDITSYSCALL
uid_t loginuid;
unsigned int sessionid;
#endif
（23）、secure computing
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seccomp_t seccomp;
seccomp_t seccomp;
（24）、用于copy_process函数使用CLONE_PARENT 标记时
[cpp] view plain copy print?
/* Thread group tracking */
u32 parent_exec_id;
u32 self_exec_id;
/* Thread group tracking */
u32 parent_exec_id;
u32 self_exec_id;
（25）、中断
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#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
#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
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/* Protection of the PI data structures: */
raw_spinlock_t pi_lock;
/* Protection of the PI data structures: */
raw_spinlock_t pi_lock;
（27）、基于PI协议的等待互斥锁，其中PI指的是priority inheritance（优先级继承）
[cpp] view plain copy print?
#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_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）、死锁检测
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#ifdef CONFIG_DEBUG_MUTEXES
/* mutex deadlock detection */
struct mutex_waiter blocked_on;
#endif
#ifdef CONFIG_DEBUG_MUTEXES
/ mutex deadlock detection */
struct mutex_waiter *blocked_on;
#endif
（29）、lockdep，参见内核说明文档linux-2.6.38.8/Documentation/lockdep-design.txt
[cpp] view plain copy print?
#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
#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
（30）、JFS文件系统
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/* journalling filesystem info */
void journal_info;
/ journalling filesystem info */
void *journal_info;
（31）、块设备链表
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/* stacked block device info */
struct bio_list *bio_list;
/* stacked block device info */
struct bio_list *bio_list;
（32）、内存回收
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struct reclaim_state *reclaim_state;
struct reclaim_state *reclaim_state;
（33）、存放块设备I/O数据流量信息
[cpp] view plain copy print?
struct backing_dev_info *backing_dev_info;
struct backing_dev_info *backing_dev_info;
（34）、I/O调度器所使用的信息
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struct io_context *io_context;
struct io_context *io_context;
（35）、记录进程的I/O计数
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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
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Ubuntu 11.04上，执行cat获得进程1的I/O计数如下：
[cpp] view plain copy print?
$ sudo cat /proc/1/io
$ sudo cat /proc/1/io
[cpp] view plain copy print?
rchar: 164258906
wchar: 455212837
syscr: 388847
syscw: 92563
read_bytes: 439251968
write_bytes: 14143488
cancelled_write_bytes: 2134016
rchar: 164258906
wchar: 455212837
syscr: 388847
syscw: 92563
read_bytes: 439251968
write_bytes: 14143488
cancelled_write_bytes: 2134016
输出的数据项刚好是task_io_accounting结构体的所有成员。
（36）、CPUSET功能
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#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
#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
（37）、Control Groups
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#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
#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
（38）、futex同步机制
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#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_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
（39）、非一致内存访问（NUMA Non-Uniform Memory Access）
[cpp] view plain copy print?
#ifdef CONFIG_NUMA
struct mempolicy mempolicy; / Protected by alloc_lock */
short il_next;
#endif
#ifdef CONFIG_NUMA
struct mempolicy mempolicy; / Protected by alloc_lock */
short il_next;
#endif
（40）、文件系统互斥资源
[cpp] view plain copy print?
atomic_t fs_excl; /* holding fs exclusive resources */
atomic_t fs_excl; /* holding fs exclusive resources */
（41）、RCU链表
[cpp] view plain copy print?
struct rcu_head rcu;
struct rcu_head rcu;
（42）、管道
[cpp] view plain copy print?
struct pipe_inode_info *splice_pipe;
struct pipe_inode_info *splice_pipe;
（43）、延迟计数
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#ifdef CONFIG_TASK_DELAY_ACCT
struct task_delay_info *delays;
#endif
#ifdef CONFIG_TASK_DELAY_ACCT
struct task_delay_info *delays;
#endif
（44）、fault injection，参考内核说明文件linux-2.6.38.8/Documentation/fault-injection/fault-injection.txt
[cpp] view plain copy print?
#ifdef CONFIG_FAULT_INJECTION
int make_it_fail;
#endif
#ifdef CONFIG_FAULT_INJECTION
int make_it_fail;
#endif
（45）、FLoating proportions
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struct prop_local_single dirties;
struct prop_local_single dirties;
（46）、Infrastructure for displayinglatency
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#ifdef CONFIG_LATENCYTOP
int latency_record_count;
struct latency_record latency_record[LT_SAVECOUNT];
#endif
#ifdef CONFIG_LATENCYTOP
int latency_record_count;
struct latency_record latency_record[LT_SAVECOUNT];
#endif
（47）、time slack values，常用于poll和select函数
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unsigned long timer_slack_ns;
unsigned long default_timer_slack_ns;
unsigned long timer_slack_ns;
unsigned long default_timer_slack_ns;
（48）、socket控制消息（control message）
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struct list_head *scm_work_list;
struct list_head *scm_work_list;
（49）、ftrace跟踪器
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#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 */