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cgroups: add per-thread subsystem callbacks

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Add cgroup subsystem callbacks for per-thread attachment in atomic contexts

Add can_attach_task(), pre_attach(), and attach_task() as new callbacks
for cgroups's subsystem interface.  Unlike can_attach and attach, these
are for per-thread operations, to be called potentially many times when
attaching an entire threadgroup.

Also, the old "bool threadgroup" interface is removed, as replaced by
this.  All subsystems are modified for the new interface - of note is
cpuset, which requires from/to nodemasks for attach to be globally scoped
(though per-cpuset would work too) to persist from its pre_attach to
attach_task and attach.

This is a pre-patch for cgroup-procs-writable.patch.

Signed-off-by: Ben Blum <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Li Zefan <[email protected]>
Cc: Matt Helsley <[email protected]>
Reviewed-by: Paul Menage <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Miao Xie <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Ben Blum 2011-05-26 16:25:19 -07:00 • committed by Linus Torvalds
commit f780bdb7c1
9 changed files with 114 additions and 142 deletions
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30
Documentation/cgroups/cgroups.txt
View file

@ -575,7 +575,7 @@ rmdir() will fail with it. From this behavior, pre_destroy() can be
called multiple times against a cgroup.
int can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct task_struct *task, bool threadgroup)
struct task_struct *task)
(cgroup_mutex held by caller)
Called prior to moving a task into a cgroup; if the subsystem
@ -584,9 +584,14 @@ task is passed, then a successful result indicates that *any*
unspecified task can be moved into the cgroup. Note that this isn't
called on a fork. If this method returns 0 (success) then this should
remain valid while the caller holds cgroup_mutex and it is ensured that either
attach() or cancel_attach() will be called in future. If threadgroup is
true, then a successful result indicates that all threads in the given
thread's threadgroup can be moved together.
attach() or cancel_attach() will be called in future.
int can_attach_task(struct cgroup *cgrp, struct task_struct *tsk);
(cgroup_mutex held by caller)
As can_attach, but for operations that must be run once per task to be
attached (possibly many when using cgroup_attach_proc). Called after
can_attach.
void cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct task_struct *task, bool threadgroup)
@ -598,15 +603,24 @@ function, so that the subsystem can implement a rollback. If not, not necessary.
This will be called only about subsystems whose can_attach() operation have
succeeded.
void pre_attach(struct cgroup *cgrp);
(cgroup_mutex held by caller)
For any non-per-thread attachment work that needs to happen before
attach_task. Needed by cpuset.
void attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct cgroup *old_cgrp, struct task_struct *task,
bool threadgroup)
struct cgroup *old_cgrp, struct task_struct *task)
(cgroup_mutex held by caller)
Called after the task has been attached to the cgroup, to allow any
post-attachment activity that requires memory allocations or blocking.
If threadgroup is true, the subsystem should take care of all threads
in the specified thread's threadgroup. Currently does not support any
void attach_task(struct cgroup *cgrp, struct task_struct *tsk);
(cgroup_mutex held by caller)
As attach, but for operations that must be run once per task to be attached,
like can_attach_task. Called before attach. Currently does not support any
subsystem that might need the old_cgrp for every thread in the group.
void fork(struct cgroup_subsy *ss, struct task_struct *task)