Messages in this thread | | | Date | Fri, 07 Nov 2008 14:58:53 +0800 | From | Li Zefan <> | Subject | Re: [PATCH -last version] freezer_cg: disable writing freezer.state of root cgroup |
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> I would make a small macro is_root_freezer() to show explicitly > what we are testing and use the CSS_ROOT bit to test. That's what > the CSS_ROOT bit is for Paul ? >
I think yes CSS_ROOT can be used, though currently CSS_ROOT is used in cgroup internal only (in css_get() and css_put()).
> if yes, here's a possible result is below. >
is_root_freezer() looks a bit better, but I don't have strong option about this change, the original code and the comment is enough to explain what we are doing.
> C. > > Signed-off-by: Cedric Le Goater <clg@fr.ibm.com> > --- > kernel/cgroup_freezer.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > Index: 2.6.27-lxc/kernel/cgroup_freezer.c > =================================================================== > --- 2.6.27-lxc.orig/kernel/cgroup_freezer.c > +++ 2.6.27-lxc/kernel/cgroup_freezer.c > @@ -47,6 +47,11 @@ static inline struct freezer *task_freez > struct freezer, css); > } > > +static inline int is_root_freezer(struct freezer *freezer) > +{ > + return test_bit(CSS_ROOT, &freezer->css.flags); > +} > + > int cgroup_frozen(struct task_struct *task) > { > struct freezer *freezer; > @@ -190,6 +195,13 @@ static void freezer_fork(struct cgroup_s > freezer = task_freezer(task); > task_unlock(task); > > + /* > + * The root cgroup is non-freezable, so we can skip the > + * following check. > + */ > + if (is_root_freezer(freezer)) > + return; > + > BUG_ON(freezer->state == CGROUP_FROZEN); > spin_lock_irq(&freezer->lock); > /* Locking avoids race with FREEZING -> THAWED transitions. */ > @@ -363,6 +375,9 @@ static struct cftype files[] = { > > static int freezer_populate(struct cgroup_subsys *ss, struct cgroup *cgroup) > { > + if (is_root_freezer(cgroup_freezer(cgroup))) > + return 0; > + > return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files)); > } >
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