admin-guide/cgroup-v1/cgroups.rst

34 	3.3 Subsystem API
53 A *subsystem* is a module that makes use of the task grouping
55 particular ways. A subsystem is typically a "resource controller" that
58 virtualization subsystem.
62 hierarchy, and a set of subsystems; each subsystem has system-specific
109 At one extreme, each resource controller or subsystem could be in a
181    cgroup_subsys_state objects, one for each cgroup subsystem
186    subsystem state is something that's expected to happen frequently
219 It's not currently possible to bind a new subsystem to an active
220 cgroup hierarchy, or to unbind a subsystem from an active cgroup
233 for each active hierarchy, the subsystem names and the cgroup name
315 the "cpuset" cgroup subsystem, the steps are something like::
437 has processes attached, or is held alive by other subsystem-specific
487 you give a subsystem a name.
489 The name of the subsystem appears as part of the hierarchy description
499 Each kernel subsystem that wants to hook into the generic cgroup
502 with a subsystem ID which will be assigned by the cgroup system.
506 - subsys_id: a unique array index for the subsystem, indicating which
507   entry in cgroup->subsys[] this subsystem should be managing.
509 - name: should be initialized to a unique subsystem name. Should be
512 - early_init: indicate if the subsystem needs early initialization
516 indexed by subsystem ID; this pointer is entirely managed by the
517 subsystem; the generic cgroup code will never touch this pointer.
538 3.3 Subsystem API
541 Each subsystem should:
546 Each subsystem may export the following methods. The only mandatory
553 Called to allocate a subsystem state object for a cgroup. The
554 subsystem should allocate its subsystem state object for the passed
556 ERR_PTR() value. On success, the subsystem pointer should point to
558 larger subsystem-specific object), which will be initialized by the
560 create the root subsystem state for this subsystem; this case can be
570 subsystem may choose to fail creation by returning -errno. This
580 @cgrp. @cgrp is being removed and the subsystem should start dropping
583 callback, @cgrp should be considered dead to the subsystem.
588 The cgroup system is about to free @cgrp; the subsystem should free
589 its subsystem state object. By the time this method is called, @cgrp
592 subsystem's create() method has been called for the new cgroup).
598 subsystem returns an error, this will abort the attach operation.
620 when a subsystem is disabled on a cgroup through
624 that the hidden subsystem can return to the initial neutral state.
633 A subsystem whose can_attach() has some side-effects should provide this
634 function, so that the subsystem can implement a rollback. If not, not necessary.
660 Called when a cgroup subsystem is rebound to a different hierarchy