Hi Konstantin and Peter, Just checking if this version was OK with you - I hadn't heard anything and I noticed it's not in -next so I just wanted to check to see if there were any other changes you wanted.
Regards, Daniel Daniel Axtens <[email protected]> writes: > If we set a next or last buddy for a se that is not on_rq, we will > end up taking a NULL pointer dereference in wakeup_preempt_entity > via pick_next_task_fair. > > Detect when we would be about to do that, throw a warning and > then refuse to actually set it. > > This has been suggested at least twice[0][1]: just do it. > > [0] https://marc.info/?l=linux-kernel&m=146651668921468&w=2 > [1] https://lkml.org/lkml/2016/6/16/663 > > Cc: Konstantin Khlebnikov <[email protected]> > Cc: Ben Segall <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Signed-off-by: Daniel Axtens <[email protected]> > > --- > > I recently had to debug a problem with these (we hadn't backported > Konstantin's patches in this area) and this would have saved a lot > of time/pain. > > v2: use SCHED_WARN_ON to restrict when the test is run. This is a > macro for WARN_ON_ONCE, which is convenient. > --- > kernel/sched/fair.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index d71109321841..44b94cfe02cb 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6168,8 +6168,11 @@ static void set_last_buddy(struct sched_entity *se) > if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) > return; > > - for_each_sched_entity(se) > + for_each_sched_entity(se) { > + if (SCHED_WARN_ON(!se->on_rq)) > + return; > cfs_rq_of(se)->last = se; > + } > } > > static void set_next_buddy(struct sched_entity *se) > @@ -6177,8 +6180,11 @@ static void set_next_buddy(struct sched_entity *se) > if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) > return; > > - for_each_sched_entity(se) > + for_each_sched_entity(se) { > + if (SCHED_WARN_ON(!se->on_rq)) > + return; > cfs_rq_of(se)->next = se; > + } > } > > static void set_skip_buddy(struct sched_entity *se) > -- > 2.11.0
