Messages in this thread | | | Subject | Re: [PATCH tip/core/urgent] rcu: protect fork-time cgroup access | From | Peter Zijlstra <> | Date | Tue, 30 Mar 2010 10:50:34 +0200 |
| |
On Mon, 2010-03-29 at 15:43 -0700, Paul Menage wrote: > On Mon, Mar 29, 2010 at 2:15 PM, Paul E. McKenney > <paulmck@linux.vnet.ibm.com> wrote: > > Add an rcu_read_lock() / rcu_read_unlock() pair to protect a fork-time > > cgroup access. This seems likely to be a false positive. > > > > Located by: Alessio Igor Bogani <abogani@texware.it> > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > --- > > > > sched.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/kernel/sched.c b/kernel/sched.c > > index 9ab3cd7..d4bb5e0 100644 > > --- a/kernel/sched.c > > +++ b/kernel/sched.c > > @@ -2621,7 +2621,9 @@ void sched_fork(struct task_struct *p, int clone_flags) > > if (p->sched_class->task_fork) > > p->sched_class->task_fork(p); > > > > + rcu_read_lock(); > > set_task_cpu(p, cpu); > > + rcu_read_unlock(); > > I think you're right that this is a false positive - it would only be > a problem if it were possible for the task to be moved to a different > cgroup, and I think that shouldn't be the case at this point in the > fork path since the new process isn't visible on the tasklist yet, > right?
Well the thing is, this fork time invocation of set_task_cpu()->set_task_rq() is in no way special, there's multiple places like that.
| |