Hi Phil, On 2023-10-09 at 10:27:40 -0400, Phil Auld wrote: > On Sat, Oct 07, 2023 at 02:42:10PM +0800 Chen Yu wrote: > > Hi Biju, > > > > On 2023-10-07 at 06:26:05 +0000, Biju Das wrote: > > > Hi Chen Yu, > > > > > > > Subject: Re: [PATCH] sched/fair: fix pick_eevdf to always find the correct > > > > se > > > > > > > > On 2023-10-06 at 21:24:45 +0200, Peter Zijlstra wrote: > > > > > On Fri, Oct 06, 2023 at 05:55:01PM +0200, Peter Zijlstra wrote: > > > > > > > > > > > And yeah, min_deadline is hosed somehow. > > > > > > > > > > > > migration/28-185 [028] d..2. 70.264274: validate_cfs_rq: --- / > > > > > > migration/28-185 [028] d..2. 70.264277: __print_se: > > > > ffff88845cf48080 w: 1024 ve: -58857638 lag: 870381 vd: -55861854 vmd: - > > > > 66302085 E (11372/tr) > > > > > > migration/28-185 [028] d..2. 70.264280: __print_se: > > > > ffff88810d165800 w: 25 ve: -80323686 lag: 22336429 vd: -41496434 vmd: - > > > > 66302085 E (-1//autogroup-31) > > > > > > migration/28-185 [028] d..2. 70.264282: __print_se: > > > > ffff888108379000 w: 25 ve: 0 lag: -57987257 vd: 114632828 vmd: 114632828 N > > > > (-1//autogroup-33) > > > > > > migration/28-185 [028] d..2. 70.264283: validate_cfs_rq: > > > > min_deadline: -55861854 avg_vruntime: -62278313462 / 1074 = -57987256 > > > > > > > > > > > > I need to go make dinner (kids hungry), but I'll see if I can figure > > > > > > out how this happens... > > > > > > > > > > *sigh*, does the below help? > > > > > > > > > > --- > > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index > > > > > 04fbcbda97d5..6a670f119efa 100644 > > > > > --- a/kernel/sched/fair.c > > > > > +++ b/kernel/sched/fair.c > > > > > @@ -3632,6 +3747,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, > > > > struct sched_entity *se, > > > > > */ > > > > > deadline = div_s64(deadline * old_weight, weight); > > > > > se->deadline = se->vruntime + deadline; > > > > > + min_deadline_cb_propagate(&se->run_node, NULL); > > > > > } > > > > > > > > > > #ifdef CONFIG_SMP > > > > > > > > Is it because without this patch, the se->deadline is not always synced > > > > with se->min_deadline, then in pick_eevdf() the following condition could > > > > not be met, thus we get a NULL candidate and has to pick the leftmost one? > > > > if (se->deadline == se->min_deadline) > > > > > > > > Regarding the circular locking warning triggered by printk, does it mean we > > > > should not get a NULL candidate from __pick_eevdf() in theory? And besides, > > > > we should not use printk with rq lock hold? > > > > > > Is it not a useful error log? At least from the initial report Marek Szyprowski doesn't see "EEVDF scheduling fail, picking leftmost" but seen only warning triggered by this in the logs. > > > > > > > Yes, it is a useful log. I was trying to figure out the safe scenario to use > > printk. > > > > You should not use printk with a rq lock held as some console implementations > (framebuffer etc) call schedule_work() which loops back into the scheduler > and bad things happen. > > Some places in the scheduler use printk_deferred() when needed. > > I think this will be better when the RT printk stuff is fully merged. > I see, got it! Thanks for the education. thanks, Chenyu
