[PATCH pm-freezer 1/4] cgroup_freezer: fix freezer->state setting bug in freezer_change_state()
oleg at redhat.com
Fri Sep 2 10:15:17 PDT 2011
On 09/03, Tejun Heo wrote:
> On Fri, Sep 02, 2011 at 06:58:39PM +0200, Oleg Nesterov wrote:
> > > This still doesn't look quite right. If the cgroup is FREEZING it should
> > > also call try_to_freeze_cgroup(). I think this is what's needed:
> > >
> > > if (freezer->state == CGROUP_THAWED)
> > > atomic_inc(&system_freezing_cnt);
> > > freezer->state = CGROUP_FREEZING;
> > > retval = try_to_freeze_cgroup(cgroup, freezer);
> > This is what I mentioned before, to me this looks like a win.
> > Why do we need try_to_freeze_cgroup() in this case? "for safety"
> > could actually mean "hide the bug" ;)
> I guess it depends on the viewpoint. A simple analogy would be using
> WARN_ON_ONCE() instead of BUG_ON() so that the mode of failure is
> softer. This change isn't likely to make bugs significantly more
> difficult to discover so why not?
I agree either way.
Personally I prefer your current patch. Because it is not clear why
do we call try_to_freeze_cgroup() if it was already called. And, the
2nd call can silently hide the problem if we have some bug.
But of course, this is up to you and Matt.
> > But I agree either way. Rafael, I think 1-4 are fine, but I think
> > we need the simple 5/4, will send in a minute...
> Can you please wait a bit? The second one was broken (missing unlock)
Yes, I just noticed the small problem too, hopefully we mean the same
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