/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _LINUX_PID_H #define _LINUX_PID_H #include enum pid_type { PIDTYPE_PID, PIDTYPE_PGID, PIDTYPE_SID, PIDTYPE_MAX, /* only valid to __task_pid_nr_ns() */ __PIDTYPE_TGID }; /* * What is struct pid? * * A struct pid is the kernel's internal notion of a process identifier. * It refers to individual tasks, process groups, and sessions. While * there are processes attached to it the struct pid lives in a hash * table, so it and then the processes that it refers to can be found * quickly from the numeric pid value. The attached processes may be * quickly accessed by following pointers from struct pid. * * Storing pid_t values in the kernel and referring to them later has a * problem. The process originally with that pid may have exited and the * pid allocator wrapped, and another process could have come along * and been assigned that pid. * * Referring to user space processes by holding a reference to struct * task_struct has a problem. When the user space process exits * the now useless task_struct is still kept. A task_struct plus a * stack consumes around 10K of low kernel memory. More precisely * this is THREAD_SIZE + sizeof(struct task_struct). By comparison * a struct pid is about 64 bytes. * * Holding a reference to struct pid solves both of these problems. * It is small so holding a reference does not consume a lot of * resources, and since a new struct pid is allocated when the numeric pid * value is reused (when pids wrap around) we don't mistakenly refer to new * processes. */ /* * struct upid is used to get the id of the struct pid, as it is * seen in particular namespace. Later the struct pid is found with * find_pid_ns() using the int nr and struct pid_namespace *ns. */ struct upid { int nr; struct pid_namespace *ns; }; struct pid { atomic_t count; unsigned int level; /* lists of tasks that use this pid */ struct hlist_head tasks[PIDTYPE_MAX]; struct rcu_head rcu; struct upid numbers[1]; }; extern struct pid init_struct_pid; struct pid_link { struct hlist_node node; struct pid *pid; }; static inline struct pid *get_pid(struct pid *pid) { if (pid) atomic_inc(&pid->count); return pid; } extern void put_pid(struct pid *pid); extern struct task_struct *pid_task(struct pid *pid, enum pid_type); extern struct task_struct *get_pid_task(struct pid *pid, enum pid_type); extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type); /* * these helpers must be called with the tasklist_lock write-held. */ extern void attach_pid(struct task_struct *task, enum pid_type); extern void detach_pid(struct task_struct *task, enum pid_type); extern void change_pid(struct task_struct *task, enum pid_type, struct pid *pid); extern void transfer_pid(struct task_struct *old, struct task_struct *new, enum pid_type); struct pid_namespace; extern struct pid_namespace init_pid_ns; /* * look up a PID in the hash table. Must be called with the tasklist_lock * or rcu_read_lock() held. * * find_pid_ns() finds the pid in the namespace specified * find_vpid() finds the pid by its virtual id, i.e. in the current namespace * * see also find_task_by_vpid() set in include/linux/sched.h */ extern struct pid *find_pid_ns(int nr, struct pid_namespace *ns); extern struct pid *find_vpid(int nr); /* * Lookup a PID in the hash table, and return with it's count elevated. */ extern struct pid *find_get_pid(int nr); extern struct pid *find_ge_pid(int nr, struct pid_namespace *); int next_pidmap(struct pid_namespace *pid_ns, unsigned int last); extern struct pid *alloc_pid(struct pid_namespace *ns); extern void free_pid(struct pid *pid); extern void disable_pid_allocation(struct pid_namespace *ns); /* * ns_of_pid() returns the pid namespace in which the specified pid was * allocated. * * NOTE: * ns_of_pid() is expected to be called for a process (task) that has * an attached 'struct pid' (see attach_pid(), detach_pid()) i.e @pid * is expected to be non-NULL. If @pid is NULL, caller should handle * the resulting NULL pid-ns. */ static inline struct pid_namespace *ns_of_pid(struct pid *pid) { struct pid_namespace *ns = NULL; if (pid) ns = pid->numbers[pid->level].ns; return ns; } /* * is_child_reaper returns true if the pid is the init process * of the current namespace. As this one could be checked before * pid_ns->child_reaper is assigned in copy_process, we check * with the pid number. */ static inline bool is_child_reaper(struct pid *pid) { return pid->numbers[pid->level].nr == 1; } /* * the helpers to get the pid's id seen from different namespaces * * pid_nr() : global id, i.e. the id seen from the init namespace; * pid_vnr() : virtual id, i.e. the id seen from the pid namespace of * current. * pid_nr_ns() : id seen from the ns specified. * * see also task_xid_nr() etc in include/linux/sched.h */ static inline pid_t pid_nr(struct pid *pid) { pid_t nr = 0; if (pid) nr = pid->numbers[0].nr; return nr; } pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns); pid_t pid_vnr(struct pid *pid); #define do_each_pid_task(pid, type, task) \ do { \ if ((pid) != NULL) \ hlist_for_each_entry_rcu((task), \ &(pid)->tasks[type], pids[type].node) { /* * Both old and new leaders may be attached to * the same pid in the middle of de_thread(). */ #define while_each_pid_task(pid, type, task) \ if (type == PIDTYPE_PID) \ break; \ } \ } while (0) #define do_each_pid_thread(pid, type, task) \ do_each_pid_task(pid, type, task) { \ struct task_struct *tg___ = task; \ for_each_thread(tg___, task) { #define while_each_pid_thread(pid, type, task) \ } \ task = tg___; \ } while_each_pid_task(pid, type, task) #endif /* _LINUX_PID_H */ ue='linux-6.13.y'>linux-6.13.y Hosts the 0x221E linux distro kernel.Ubuntu
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AgeCommit message (Expand)Author
2025-09-15Input: add INPUT_PROP_HAPTIC_TOUCHPADAngela Czubak
2025-07-27Input: Add and document BTN_GRIP*Vicki Pfau
2025-07-27Documentation: Fix capitalization of XBox -> XboxVicki Pfau
2025-07-01Input: edt-ft5x06 - use per-client debugfs directoryWolfram Sang
2025-05-30Input: amijoy - make headings compliant w/ guidelines in documentationGeorge Anthony Vernon
2025-05-30Input: amijoy - fix grammar in documentationGeorge Anthony Vernon
2025-05-30Input: amijoy - fix Amiga 4-joystick adapter pinout in documentationGeorge Anthony Vernon
2025-05-30Input: amijoy - fix broken table formatting in documentationGeorge Anthony Vernon
2025-02-21Documentation: input: Add section pertaining to polled input devicesBrendan Connelly
2025-02-18Documentation: typo fixesArmin Mahdilou
2024-11-14Input: fix the input_event struct documentationMaud Spierings
2023-11-17input: docs: properly format ToC headingsVegard Nossum
2023-08-28input: docs: pxrc: remove reference to phoenix-simMarcus Folkesson
2023-08-18Documentation: Fix typosBjorn Helgaas
2023-05-22Input: xpad - spelling fixes for "Xbox"Ismael Ferreras Morezuelas
2023-01-24Docs/subsystem-apis: Remove '[The ]Linux' prefixes from titles of listed docu...SeongJae Park
2022-10-09Merge branch 'next' into for-linusDmitry Torokhov
2022-09-28Input: add ABS_PROFILE to uapi and documentationNate Yocom
2022-08-29Input: iforce - add support for Boeder Force Feedback WheelGreg Tulli
2022-06-01documentation: Format button_dev as a pointer.Nelson Penn
2022-05-17input: Docs: correct ntrig.rst typoRandy Dunlap
2022-05-17input: Docs: correct atarikbd.rst typosRandy Dunlap
2022-03-01Input: docs: add more details on the use of BTN_TOOLBenjamin Tissoires
2021-06-04docs: networking: Replace strncpy() with strscpy()Kees Cook
2021-05-06Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dto...Linus Torvalds
2021-05-03Documentation: input: joydev file correctionsRandy Dunlap
2021-03-25Merge tag 'v5.12-rc4' into nextDmitry Torokhov
2021-03-25Input: rotary-encoder - update docs according to the latest API changesHeikki Krogerus
2021-03-08input: Documentation: corrections for uinput.rstRandy Dunlap
2021-03-08input: Documentation: corrections for input-programming.rstRandy Dunlap
2021-03-08input: Documentation: corrections for notifier.rstRandy Dunlap
2021-03-08input: Documentation: corrections for multi-touch-protocol.rstRandy Dunlap
2021-03-08input: Documentation: corrections for gameport-programming.rstRandy Dunlap
2021-03-08input: Documentation: update related file names in ff.rstRandy Dunlap
2021-03-08input: Documentation: corrections for event-codes.rstRandy Dunlap
2021-03-08input: Documentation: corrections for input.rstRandy Dunlap