From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay2-d.mail.gandi.net (relay2-d.mail.gandi.net [217.70.183.194]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 18B5131F9AB for ; Thu, 18 Jun 2026 08:20:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.183.194 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781770807; cv=none; b=cNnfpI0m0eVEDmZk+ik6vWmf/vIyMTLDgVuQq+udEMIRf+ccFAFXUKkrkpYd4Ux/+rsMBrxMYc8kzUcCjiqSuHOz34GLxt3CZ7j6Mn0u81LY03RIb7YbjpYfJHCuYS+ySDLgt/nwWCyUx8k/ojl3+VCyZ34tQW1kV2RL+1jb2Io= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781770807; c=relaxed/simple; bh=a7WaQaDmpoEgeuHAV+vRhy8ZGTXfrGbgSa0Ebo7V9w8=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=jS1GZPZqUMROx0tKIxyGCg3RZ/aoA238lsstmWJtBhFD1u9S+LeeyMa7TP3hBm89wsm1aBU+K3F1Nscs7p2twf9DdeApjg3xGIkF1e345ufSdCNUalHW1gL+FizaTOQInP0ukT4/8yensnOBwa2pWtlJzmaLlPqzkEFl9OmWljs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=xenomai.org; spf=pass smtp.mailfrom=xenomai.org; dkim=pass (2048-bit key) header.d=xenomai.org header.i=@xenomai.org header.b=awnxzeNV; arc=none smtp.client-ip=217.70.183.194 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=xenomai.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=xenomai.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=xenomai.org header.i=@xenomai.org header.b="awnxzeNV" Received: by mail.gandi.net (Postfix) with ESMTPSA id 032AF3EBB4; Thu, 18 Jun 2026 08:20:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=xenomai.org; s=gm1; t=1781770801; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=kPdKnwJmosr5+jDDyvmfVPvP1WvqwqsNbfCrv6GkWUg=; b=awnxzeNVXj7ZQvfKI4nKghajW91snhXFYh5HMU8u60BGRGw7pKiWIdoWaTgdunTfvTZ6Yk Cs0KToLWHUc0zS2ozKsld2DBV/hBCi8/SX7alebBf4DER7mia5nAZCvcgO7hmMojIn5uJS fazxyz9/7eIfFGm9+MuBRmNLOzl3U6iDC/t+ylquJKEvqAgQCVFIWFwquezbaoQRcqxFjC RlGmmJQqJkMSJeBE569bLmOzvn6E+igtCmCYn4Psa0Om6+Y31K6tL4VsVd/MPOouUeVu0c Jr7G4Nb/CMs0Np0PMxekckrYqEUGevuTndr8zs6f1LGRa/2j+5vyRm6WipK4xA== From: Philippe Gerum To: Jan Kiszka Cc: xenomai@lists.linux.dev Subject: Re: [PATCH v1 1/2] evl/sched: core: introduce schedule out handler In-Reply-To: <87a4sss1qi.fsf@xenomai.org> (Philippe Gerum's message of "Thu, 18 Jun 2026 10:15:49 +0200") References: <20260617142050.477809-1-rpm@xenomai.org> <20260617142050.477809-2-rpm@xenomai.org> <87ik7gs367.fsf@xenomai.org> <87a4sss1qi.fsf@xenomai.org> User-Agent: mu4e 1.12.12; emacs 30.2 Date: Thu, 18 Jun 2026 10:20:00 +0200 Message-ID: <874ij0s1jj.fsf@xenomai.org> Precedence: bulk X-Mailing-List: xenomai@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-GND-Sasl: rpm@xenomai.org X-GND-State: clean X-GND-Score: -100 X-GND-Cause: 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 Philippe Gerum writes: > Jan Kiszka writes: > >> On 18.06.26 09:44, Philippe Gerum wrote: >>> Jan Kiszka writes: >>> >>>> On 17.06.26 16:20, Philippe Gerum wrote: >>>>> From: Philippe Gerum >>>>> >>>>> Some scheduling classes may need a way to perform specific >>>>> fixup/accounting work for a thread which is being scheduled out. We >>>>> cannot rely on the sched_pick() handler for this since the first one >>>>> to successfully pick a thread prevents other handlers down the class >>>>> hierarchy to run. >>>>> >>>>> To address this issue, we introduce the sched_out() handler which is >>>>> called for the current thread when scheduled out. This handler is >>>>> invoked unconditionally when present prior to picking a new thread. >>>>> >>>>> Signed-off-by: Philippe Gerum >>>>> --- >>>>> include/evl/sched.h | 1 + >>>>> kernel/evl/sched/core.c | 20 +++++++++++++------- >>>>> 2 files changed, 14 insertions(+), 7 deletions(-) >>>>> >>>>> diff --git a/include/evl/sched.h b/include/evl/sched.h >>>>> index ae9690860146..cc824c28004b 100644 >>>>> --- a/include/evl/sched.h >>>>> +++ b/include/evl/sched.h >>>>> @@ -120,6 +120,7 @@ struct evl_sched_class { >>>>> void (*sched_dequeue)(struct evl_thread *thread); >>>>> void (*sched_requeue)(struct evl_thread *thread); >>>>> struct evl_thread *(*sched_pick)(struct evl_rq *rq); >>>>> + void (*sched_out)(struct evl_thread *thread); >>>>> void (*sched_yield)(struct evl_thread *thread); >>>>> void (*sched_migrate)(struct evl_thread *thread, >>>>> struct evl_rq *rq); >>>>> diff --git a/kernel/evl/sched/core.c b/kernel/evl/sched/core.c >>>>> index d1d025e06a5d..7127d4e52df9 100644 >>>>> --- a/kernel/evl/sched/core.c >>>>> +++ b/kernel/evl/sched/core.c >>>>> @@ -773,7 +773,8 @@ static inline void set_next_running(struct evl_rq *rq, >>>>> evl_stop_timer(&rq->rrbtimer); >>>>> } >>>>> >>>>> -static struct evl_thread *__pick_next_thread(struct evl_rq *rq) >>>>> +static __always_inline struct evl_thread * >>>>> +__pick_next_thread(struct evl_rq *rq) >>>>> { >>>>> struct evl_sched_class *sched_class; >>>>> struct evl_thread *curr = rq->curr; >>>>> @@ -821,8 +822,14 @@ static struct evl_thread *__pick_next_thread(struct evl_rq *rq) >>>>> /* rq->curr->lock + rq->lock held, hard irqs off. */ >>>>> static struct evl_thread *pick_next_thread(struct evl_rq *rq) >>>>> { >>>>> - struct evl_thread *next = __pick_next_thread(rq); >>>>> + struct evl_thread *next, *prev = rq->curr; >>>>> + struct evl_sched_class *prev_class = prev->sched_class; >>>>> >>>>> + if (prev_class->sched_out) >>>>> + prev_class->sched_out(prev); >>>>> + >>>>> + next = __pick_next_thread(rq); >>>>> + trace_evl_pick_thread(next); >>>>> set_next_running(rq, next); >>>>> >>>>> return next; >>>>> @@ -972,21 +979,20 @@ void __evl_schedule(void) /* oob or/and hard irqs off (CPU migration-safe) */ >>>>> return; >>>>> } >>>>> >>>>> + prev = curr; >>>>> next = pick_next_thread(this_rq); >>>>> - trace_evl_pick_thread(next); >>>>> - if (next == curr) { >>>>> - if (unlikely(next->state & EVL_T_ROOT)) { >>>>> + if (next == prev) { >>>>> + if (unlikely(prev->state & EVL_T_ROOT)) { >>>>> if (this_rq->local_flags & RQ_TPROXY) >>>>> evl_notify_proxy_tick(this_rq); >>>>> if (this_rq->local_flags & RQ_TDEFER) >>>>> evl_program_local_tick(&evl_mono_clock); >>>>> } >>>>> raw_spin_unlock(&this_rq->lock); >>>>> - raw_spin_unlock_irqrestore(&curr->lock, flags); >>>>> + raw_spin_unlock_irqrestore(&prev->lock, flags); >>>>> return; >>>>> } >>>>> - >>>>> - prev = curr; >>>> >>>> This hunk subtly look like a pure cosmetic change, without any logical >>>> impact. If it does have one which I missed, it should be explained in >>>> the commit message at least. >>>> >>> >>> It has none, as mentioned earlier in a previous post. The point of this >>> change is to clarify the naming, introducing 'prev' as an alias to >>> 'curr' in the swap sequence. So there is no point in documenting this. >>> >> >> Again, it is suboptimal style to fold refactorings into logical code >> changes. If you split this up into two commits, properly explaining the >> purpose of that renaming, things become readable to 3rd parties. >> > > I understand your point of view, I simply disagree with the scope of the > requirement as you state it. So let's move on. Meanwhile, I just received a second opinion stating that this change seems vaguely troubling, raising interior alarm bells. I must be the only one to find it trivial, so ok. I'll split that, moving it to a separate patch. -- Philippe.