lkml.org 
[lkml]   [2023]   [Jan]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] sched: pick_next_rt_entity(): checked list_entry

    * Pietro Borrello <borrello@diag.uniroma1.it> wrote:

    > Commit 326587b84078 ("sched: fix goto retry in pick_next_task_rt()")
    > removed any path which could make pick_next_rt_entity() return NULL.
    > However, BUG_ON(!rt_se) in _pick_next_task_rt() (the only caller of
    > pick_next_rt_entity()) still checks the error condition, which can
    > never happen, since list_entry() never returns NULL. Return
    > list_first_entry_or_null(queue, ...) to allow BUG to check the only
    > possible error condition here: the queue being empty which should
    > never happen.
    >
    > Fixes: 326587b84078 ("sched: fix goto retry in pick_next_task_rt()")
    > Signed-off-by: Pietro Borrello <borrello@diag.uniroma1.it>
    > ---
    > kernel/sched/rt.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
    > index ed2a47e4ddae..6088d5d83b75 100644
    > --- a/kernel/sched/rt.c
    > +++ b/kernel/sched/rt.c
    > @@ -1777,7 +1777,7 @@ static struct sched_rt_entity *pick_next_rt_entity(struct rt_rq *rt_rq)
    > BUG_ON(idx >= MAX_RT_PRIO);
    >
    > queue = array->queue + idx;
    > - next = list_entry(queue->next, struct sched_rt_entity, run_list);
    > + next = list_first_entry_or_null(queue, struct sched_rt_entity, run_list);
    >
    > return next;

    I'd much rather have something like this:

    SCHED_WARN_ON(list_empty(next));

    So the debug check is part of CONFIG_SCHED_DEBUG=y, and not if it's turned
    off. Also, this makes sure we don't crash (BUG_ON()) on the error
    condition, in the hope of getting debug info out of the system.

    Thanks,

    Ingo

    \
     
     \ /
      Last update: 2023-03-27 00:02    [W:2.602 / U:0.528 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site