Messages in this thread | | | Subject | Re: [RFC][PATCH] cgroup: Fix cgroup_subsys::exit callback | From | Peter Zijlstra <> | Date | Mon, 07 Feb 2011 21:02:39 +0100 |
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On Mon, 2011-02-07 at 11:28 -0800, Paul Menage wrote: > On Mon, Feb 7, 2011 at 8:10 AM, Peter Zijlstra <peterz@infradead.org> wrote: > > > > Make the ::exit method act like ::attach, it is after all very nearly > > the same thing. > > The major difference between attach and exit is that the former is > only triggered in response to user cgroup-management action, whereas > the latter is triggered whenever a task exits, even if cgroups aren't > set up.
And the major likeness is that they both migrate a task from one cgroup to another. You cannot simply ignore that.
> > void cgroup_exit(struct task_struct *tsk, int run_callbacks) > > { > > - int i; > > struct css_set *cg; > > + int i; > > > > - if (run_callbacks && need_forkexit_callback) { > > - /* > > - * modular subsystems can't use callbacks, so no need to lock > > - * the subsys array > > - */ > > - for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) { > > - struct cgroup_subsys *ss = subsys[i]; > > - if (ss->exit) > > - ss->exit(ss, tsk); > > - } > > - } > > + mutex_lock(&cgroup_mutex); > > NACK - cgroup_mutex is way too heavy to take in the task exit path. > We'll need to find some other way to fix this if it's really needed. > task->alloc_lock is also normally a valid thing to synchronize against > cgroup moves, but I'd have to look at the exit path to see if it's > still valid there.
If maybe you're like respond more often than about once every two months I might actually care what you think.
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