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authorPaul Menage <menage@google.com>2008-02-07 03:13:45 -0500
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-07 11:42:18 -0500
commit8dc4f3e17dd5f7e59ce568155ccd8974af879315 (patch)
tree959b1197fea798c9daae4dd6c9596ab710d41fda /Documentation/cgroups.txt
parent622d42cac9ed42098aa50c53994f625abfa3d473 (diff)
cgroups: move cgroups destroy() callbacks to cgroup_diput()
Move the calls to the cgroup subsystem destroy() methods from cgroup_rmdir() to cgroup_diput(). This allows control file reads and writes to access their subsystem state without having to be concerned with locking against cgroup destruction - the control file dentry will keep the cgroup and its subsystem state objects alive until the file is closed. The documentation is updated to reflect the changed semantics of destroy(); additionally the locking comments for destroy() and some other methods were clarified and decrustified. Signed-off-by: Paul Menage <menage@google.com> Cc: Paul Jackson <pj@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/cgroups.txt')
-rw-r--r--Documentation/cgroups.txt22
1 files changed, 11 insertions, 11 deletions
diff --git a/Documentation/cgroups.txt b/Documentation/cgroups.txt
index 98a26f81fa75..42d7c4cb39cd 100644
--- a/Documentation/cgroups.txt
+++ b/Documentation/cgroups.txt
@@ -456,7 +456,7 @@ methods are create/destroy. Any others that are null are presumed to
456be successful no-ops. 456be successful no-ops.
457 457
458struct cgroup_subsys_state *create(struct cgroup *cont) 458struct cgroup_subsys_state *create(struct cgroup *cont)
459LL=cgroup_mutex 459(cgroup_mutex held by caller)
460 460
461Called to create a subsystem state object for a cgroup. The 461Called to create a subsystem state object for a cgroup. The
462subsystem should allocate its subsystem state object for the passed 462subsystem should allocate its subsystem state object for the passed
@@ -471,14 +471,19 @@ it's the root of the hierarchy) and may be an appropriate place for
471initialization code. 471initialization code.
472 472
473void destroy(struct cgroup *cont) 473void destroy(struct cgroup *cont)
474LL=cgroup_mutex 474(cgroup_mutex held by caller)
475 475
476The cgroup system is about to destroy the passed cgroup; the 476The cgroup system is about to destroy the passed cgroup; the subsystem
477subsystem should do any necessary cleanup 477should do any necessary cleanup and free its subsystem state
478object. By the time this method is called, the cgroup has already been
479unlinked from the file system and from the child list of its parent;
480cgroup->parent is still valid. (Note - can also be called for a
481newly-created cgroup if an error occurs after this subsystem's
482create() method has been called for the new cgroup).
478 483
479int can_attach(struct cgroup_subsys *ss, struct cgroup *cont, 484int can_attach(struct cgroup_subsys *ss, struct cgroup *cont,
480 struct task_struct *task) 485 struct task_struct *task)
481LL=cgroup_mutex 486(cgroup_mutex held by caller)
482 487
483Called prior to moving a task into a cgroup; if the subsystem 488Called prior to moving a task into a cgroup; if the subsystem
484returns an error, this will abort the attach operation. If a NULL 489returns an error, this will abort the attach operation. If a NULL
@@ -489,25 +494,20 @@ remain valid while the caller holds cgroup_mutex.
489 494
490void attach(struct cgroup_subsys *ss, struct cgroup *cont, 495void attach(struct cgroup_subsys *ss, struct cgroup *cont,
491 struct cgroup *old_cont, struct task_struct *task) 496 struct cgroup *old_cont, struct task_struct *task)
492LL=cgroup_mutex
493
494 497
495Called after the task has been attached to the cgroup, to allow any 498Called after the task has been attached to the cgroup, to allow any
496post-attachment activity that requires memory allocations or blocking. 499post-attachment activity that requires memory allocations or blocking.
497 500
498void fork(struct cgroup_subsy *ss, struct task_struct *task) 501void fork(struct cgroup_subsy *ss, struct task_struct *task)
499LL=callback_mutex, maybe read_lock(tasklist_lock)
500 502
501Called when a task is forked into a cgroup. Also called during 503Called when a task is forked into a cgroup. Also called during
502registration for all existing tasks. 504registration for all existing tasks.
503 505
504void exit(struct cgroup_subsys *ss, struct task_struct *task) 506void exit(struct cgroup_subsys *ss, struct task_struct *task)
505LL=callback_mutex
506 507
507Called during task exit 508Called during task exit
508 509
509int populate(struct cgroup_subsys *ss, struct cgroup *cont) 510int populate(struct cgroup_subsys *ss, struct cgroup *cont)
510LL=none
511 511
512Called after creation of a cgroup to allow a subsystem to populate 512Called after creation of a cgroup to allow a subsystem to populate
513the cgroup directory with file entries. The subsystem should make 513the cgroup directory with file entries. The subsystem should make
@@ -524,7 +524,7 @@ example in cpusets, no task may attach before 'cpus' and 'mems' are set
524up. 524up.
525 525
526void bind(struct cgroup_subsys *ss, struct cgroup *root) 526void bind(struct cgroup_subsys *ss, struct cgroup *root)
527LL=callback_mutex 527(cgroup_mutex held by caller)
528 528
529Called when a cgroup subsystem is rebound to a different hierarchy 529Called when a cgroup subsystem is rebound to a different hierarchy
530and root cgroup. Currently this will only involve movement between 530and root cgroup. Currently this will only involve movement between