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authorPaul Menage <menage@google.com>2008-02-07 00:13:45 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-07 08:42:18 -0800
commit8dc4f3e17dd5f7e59ce568155ccd8974af879315 (patch)
tree959b1197fea798c9daae4dd6c9596ab710d41fda /Documentation
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')
-rw-r--r--Documentation/cgroups.txt22
1 files changed, 11 insertions, 11 deletions
diff --git a/Documentation/cgroups.txt b/Documentation/cgroups.txt
index 98a26f81fa7..42d7c4cb39c 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
be successful no-ops.
struct cgroup_subsys_state *create(struct cgroup *cont)
-LL=cgroup_mutex
+(cgroup_mutex held by caller)
Called to create a subsystem state object for a cgroup. The
subsystem 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
initialization code.
void destroy(struct cgroup *cont)
-LL=cgroup_mutex
+(cgroup_mutex held by caller)
-The cgroup system is about to destroy the passed cgroup; the
-subsystem should do any necessary cleanup
+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).
int can_attach(struct cgroup_subsys *ss, struct cgroup *cont,
struct task_struct *task)
-LL=cgroup_mutex
+(cgroup_mutex held by caller)
Called prior to moving a task into a cgroup; if the subsystem
returns an error, this will abort the attach operation. If a NULL
@@ -489,25 +494,20 @@ remain valid while the caller holds cgroup_mutex.
void attach(struct cgroup_subsys *ss, struct cgroup *cont,
struct cgroup *old_cont, struct task_struct *task)
-LL=cgroup_mutex
-
Called after the task has been attached to the cgroup, to allow any
post-attachment activity that requires memory allocations or blocking.
void fork(struct cgroup_subsy *ss, struct task_struct *task)
-LL=callback_mutex, maybe read_lock(tasklist_lock)
Called when a task is forked into a cgroup. Also called during
registration for all existing tasks.
void exit(struct cgroup_subsys *ss, struct task_struct *task)
-LL=callback_mutex
Called during task exit
int populate(struct cgroup_subsys *ss, struct cgroup *cont)
-LL=none
Called after creation of a cgroup to allow a subsystem to populate
the 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
up.
void bind(struct cgroup_subsys *ss, struct cgroup *root)
-LL=callback_mutex
+(cgroup_mutex held by caller)
Called when a cgroup subsystem is rebound to a different hierarchy
and root cgroup. Currently this will only involve movement between