A estrutura de um processo no Linux é definida por a estrutura task_struct
Existem muitos campos nessa estrutura. Aqui está uma lista parcial, de spinics.net
- volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
represents the state of the process. Authorized states are
TASK_RUNNING, TASK_INTERRUPTIBLE, TASK_UNINTERRUPTIBLE, TASK_STOPPED,
TASK_ZOMBIE and TASK_DEAD
- struct thread_info *thread_info;
a pointer to a thread_info...
- atomic_t usage;
used by get_task_struct(). It's also set in kernel/fork.c. This value
acts like a reference count on the task structure of a process. It can be
used if we don't want to hold the tasklist_lock.
- unsigned long flags; /* per process flags, defined below */
process flag can be, for example, PF_DEAD when exit_notify() is called.
List is of possible values is in include/linux/sched.h
- unsigned long ptrace;
used by ptrace a system call that provides the ability to a parent
process to observe and control the execution of another process.
- int lock_depth; /* Lock depth */
used for big kernel lock in SMP. It's a per-process counter of acquires.
-1 means no lock.
- int prio, static_prio;
priority of a process used when scheduled. Variable prio, which is the
user-nice values, can be converted to static priority to better scale
various scheduler parameters.
- struct list_head run_list;
a list of runnable task.
- prio_array_t *array;
a pointer to a priority array.
- unsigned long sleep_avg;
average sleep time of the process
- long interactive_credit;
used to evaluate the interactivity of a task. For example, tasks that
sleep a long time are categorized as idle and will get just interactive
status to stay active and prevent them suddenly becoming cpu hogs and
starving other processes.
- unsigned long long timestamp;
keep the time when the process has been activating. It is used, for
example, to recalculate the task's priority.
- int activated;
TO-DO
- unsigned long policy;
the scheduling policy used for this process. It can be SCHED_NORMAL,
SCHED_FIFO or SCHED_RR
- cpumask_t cpus_allowed;
mask that indicates on what CPUs the process can run.
- unsigned int time_slice, first_time_slice;
time during when the process can run.
- struct list_head tasks;
double linked list of tasks in the system.
- struct list_head ptrace_children;
list of children traced by the process.
- struct list_head ptrace_list;
list of parent that traces the process.
- struct mm_struct *mm, *active_mm;
process address space describes by mm_struct. Field active_mm points to
the active address space if the process doesn't have real one (eg kernel
threads).
/* task state */
- struct linux_binfmt *binfmt;
allows to define functions that are used to load the binary formats that
linux accepts.
- int exit_code, exit_signal;
holds code or signal when a process exited.
code: SIGHUP, SIGINT, SIGQUIT, ...
signal: generally used with SIGCHLD to signal init on exit
- int pdeath_signal;
/* The signal sent when the parent dies */
/* ??? */
- unsigned long personality;
relates to the personality of the task, i.e. to the way certain system
calls behave in order to emulate the "personality" of foreign flavors of
UNIX.
- int did_exec:1;
set to 1 when executing a new program using sys_execve() and searching
the correct binary formats handler
- pid_t pid;
process identifier
- pid_t tgid;
identifier of the thread group leader
/*
* pointers to (original) parent process, youngest child, younger sibling,
* older sibling, respectively. (p->father can be replaced with
* p->parent->pid)
*/
- struct task_struct *real_parent;
/* real parent process (when being debugged) */
- struct task_struct *parent;
/* parent process */
- 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 */
/* PID/PID hash table linkage. */
- struct pid_link pids[PIDTYPE_MAX];
- wait_queue_head_t wait_chldexit;
/* for wait4() */
- struct completion *vfork_done;
/* for vfork() */
- int __user *set_child_tid;
/* CLONE_CHILD_SETTID */
TO-DO
- int __user *clear_child_tid;
/* CLONE_CHILD_CLEARTID */
TO-DO
- unsigned long rt_priority;
real time priority
- unsigned long it_real_value, it_prof_value, it_virt_value;
holds the current timer value. It's used to implement the specific
interval timer (itmer).
- unsigned long it_real_incr, it_prof_incr, it_virt_incr;
holds the duration of the interval. It's used to implement the specific
interval timer (itmer).
- struct timer_list real_timer;
a periodic timer
- unsigned long utime, stime, cutime, cstime;
utime = user time,
stime = system time,
cutime = cumulative user time (process + its children),
cstime = cumulative system time (process + its children)
- unsigned long nvcsw, nivcsw, cnvcsw, cnivcsw;
/* context switch counts */
think this fields is never update...
- u64 start_time;
value of the jiffies when the task was created
/* mm fault and swap info: this can arguably be seen as either mm-specific or
thread-specific */
- unsigned long min_flt, maj_flt, cmin_flt, cmaj_flt;
min_flt: minor fault,
maj_flt: major fault (means that it had access to the disk),
cmin_flt: cumulative minor fault (process + its children),
cmaj_flt: cumulative major fault (process + its children)
/* process credentials */
- uid_t uid,euid,suid,fsuid;
uid: user identifier,
euid: effective UID used for privilege checks,
suid: saved UID used to support switching permission,
fsuid: UID used for filesystem access checks (used by NFS for
example)
- gid_t gid,egid,sgid,fsgid;
gid: group identifier,
egid: effective GID used for privilege checks,
sgid: saved GID used to support switching permission,
fgid: GID used for filesystem access checks
- struct group_info *group_info;
- kernel_cap_t cap_effective, cap_inheritable, cap_permitted;
POSIX capability information. It's sets of bits that permit splitting of
the privileges typically held by root into a larger set of more specific
privileges.
- int keep_capabilities:1;
used to forbid the drop of all privileges.
- struct user_struct *user;
information about user who owns the process.
/* limits */
- struct rlimit rlim[RLIM_NLIMITS];
used to control/accounting resource usage. Resource are CPU time, maximum
file size, max data size, max stack size, max core file size, max
resident set size, man number of processes, man number of open files,
max locked-in-memory address space, address space limit and the maximum
file locks held.
- unsigned short used_math;
sets if current process can use or not the FPU.
- char comm[16];
command name.
/* file system info */
- int link_count, total_link_count;
counts the number of symbolic links.
/* ipc stuff */
- struct sysv_sem sysvsem;
/* CPU-specific state of this task */
- struct thread_struct thread;
holds information about cache TLS descriptors, debugging registers,
fault info, floating point, virtual 86 mode or IO permissions.
/* filesystem information */
- struct fs_struct *fs;
/* open file information */
- struct files_struct *files;
/* namespace */
- struct namespace *namespace;
/* signal handlers */
- struct signal_struct *signal;
signal associated to the process
- struct sighand_struct *sighand;
signal handler associated to the process
- sigset_t blocked, real_blocked;
signals that are blocked by the process