finish_task_switch() enables preemption, so post_schedule(rq) can be called on the wrong (and even dead) CPU. Afaics, nothing really bad can happen, but in this case we can wrongly clear rq->post_schedule on that CPU. And this simply looks wrong in any case.
Another problem is that finish_task_switch() itself runs with preempt enabled after finish_lock_switch(). If nothing else this means that ->sched_in() notifier can't trust its "cpu" arg. Signed-off-by: Oleg Nesterov <[email protected]> --- kernel/sched/core.c | 11 +++++------ 1 files changed, 5 insertions(+), 6 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 703c7e6..3f267e8 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2277,15 +2277,14 @@ static inline void post_schedule(struct rq *rq) asmlinkage __visible void schedule_tail(struct task_struct *prev) __releases(rq->lock) { - struct rq *rq = this_rq(); + struct rq *rq; + /* finish_task_switch() drops rq->lock and enables preemtion */ + preempt_disable(); + rq = this_rq(); finish_task_switch(rq, prev); - - /* - * FIXME: do we need to worry about rq being invalidated by the - * task_switch? - */ post_schedule(rq); + preempt_enable(); if (current->set_child_tid) put_user(task_pid_vnr(current), current->set_child_tid); -- 1.5.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
