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cgroup: rename ->create/post_create/pre_destroy/destroy() to ->css_alloc/online/offline/free()

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Rename cgroup_subsys css lifetime related callbacks to better describe
what their roles are.  Also, update documentation.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo
2012-11-19 08:13:38 -08:00
parent b1929db42f
commit 92fb97487a
13 changed files with 130 additions and 119 deletions
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45
Documentation/cgroups/cgroups.txt
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@@ -553,16 +553,16 @@ call to cgroup_unload_subsys(). It should also set its_subsys.module =
THIS_MODULE in its .c file.
Each subsystem may export the following methods. The only mandatory
methods are create/destroy. Any others that are null are presumed to
methods are css_alloc/free. Any others that are null are presumed to
be successful no-ops.
struct cgroup_subsys_state *create(struct cgroup *cgrp)
struct cgroup_subsys_state *css_alloc(struct cgroup *cgrp)
(cgroup_mutex held by caller)
Called to create a subsystem state object for a cgroup. The
Called to allocate a subsystem state object for a cgroup. The
subsystem should allocate its subsystem state object for the passed
cgroup, returning a pointer to the new object on success or a
negative error code. On success, the subsystem pointer should point to
ERR_PTR() value. On success, the subsystem pointer should point to
a structure of type cgroup_subsys_state (typically embedded in a
larger subsystem-specific object), which will be initialized by the
cgroup system. Note that this will be called at initialization to
@@ -571,24 +571,33 @@ identified by the passed cgroup object having a NULL parent (since
it's the root of the hierarchy) and may be an appropriate place for
initialization code.
void destroy(struct cgroup *cgrp)
int css_online(struct cgroup *cgrp)
(cgroup_mutex held by caller)
The cgroup system is about to destroy the passed cgroup; the subsystem
should do any necessary cleanup and free its subsystem state
object. By the time this method is called, the cgroup has already been
unlinked from the file system and from the child list of its parent;
cgroup->parent is still valid. (Note - can also be called for a
newly-created cgroup if an error occurs after this subsystem's
create() method has been called for the new cgroup).
Called after @cgrp successfully completed all allocations and made
visible to cgroup_for_each_child/descendant_*() iterators. The
subsystem may choose to fail creation by returning -errno. This
callback can be used to implement reliable state sharing and
propagation along the hierarchy. See the comment on
cgroup_for_each_descendant_pre() for details.
int pre_destroy(struct cgroup *cgrp);
void css_offline(struct cgroup *cgrp);
Called before checking the reference count on each subsystem. This may
be useful for subsystems which have some extra references even if
there are not tasks in the cgroup. If pre_destroy() returns error code,
rmdir() will fail with it. From this behavior, pre_destroy() can be
called multiple times against a cgroup.
This is the counterpart of css_online() and called iff css_online()
has succeeded on @cgrp. This signifies the beginning of the end of
@cgrp. @cgrp is being removed and the subsystem should start dropping
all references it's holding on @cgrp. When all references are dropped,
cgroup removal will proceed to the next step - css_free(). After this
callback, @cgrp should be considered dead to the subsystem.
void css_free(struct cgroup *cgrp)
(cgroup_mutex held by caller)
The cgroup system is about to free @cgrp; the subsystem should free
its subsystem state object. By the time this method is called, @cgrp
is completely unused; @cgrp->parent is still valid. (Note - can also
be called for a newly-created cgroup if an error occurs after this
subsystem's create() method has been called for the new cgroup).
int can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
(cgroup_mutex held by caller)