On Sun, May 16, 2021 at 02:01:29PM +0100, Khaled Romdhani wrote: > On Sat, May 15, 2021 at 11:02:38PM +0200, Peter Zijlstra wrote: > > On Sat, May 15, 2021 at 05:46:45PM +0100, Khaled ROMDHANI wrote: > > > The 'curr' variable could be NULL and derefrenced by > > > pick_next_entity. Fix this by adding a check that prevent > > > the invocation of pick_next_entity with a NULL passed argument. > > > > And why exactly is that a problem? > > > Within pick_next_entity, we could have 'left = curr'. > Thus the function wakeup_preempt_entity which is invoked > from pick_next_entity, derefrence the the sched entity 'left' > that may be a NULL passed argument. We call pick_next_entity() from pick_task_fair() (or pick_next_task_fair(), same argument for both), we only call it when cfs_rq->nr_running != 0. IOW we *know* there is at least one task. Therefore, if curr == NULL, we *must* have left. If you can't read code, stay away from Coverity, it's crap.
