From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 3D5794688 for ; Mon, 3 Jun 2024 15:04:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717427093; cv=none; b=Od7VcnMZVcqos2KcW1lVYodZpVGitAOKZIHm+978WL6eJUPdDBV2i51tmZG3P6LCDRZT52mVX65wJDCEWlZRykt1pZX4swLvgNOqiOO13ru3mjM5pm+3QZMDYNRxx5dzj/8jy4jStZyo2ynidWvDqtKcNCD+PMGysZwC8TwgDfM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717427093; c=relaxed/simple; bh=88kI+riU9Oh93UNPrHzY+gClgmBM46CaGhKGQnVncf4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=umUh1IspkhKe5dgzBR38GJhEwO9C4P+ng8tfHYaKoU59c01rc323RQ1i5X5mtQFJ0ec10JhoOubdOZyvq1NB3+5w37jv8IQSepyQ54acc++4OpEWL8Ru/j8bB7lEJdy0Qy2MptMoCGWCKBMtrQ74ZBj3wjDYDAJZLAvbXyscMKc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=YOYJ4t8k; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="YOYJ4t8k" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1717427091; 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=hSP7uT+GwnJuqCrKWe61V7eti5NONprO/a97gKxkynU=; b=YOYJ4t8k5eKhuJgkcUtjXZbLW8XXaO6/xibb9z4sZXeqZgCRc0GdTURw2qjdBZsGOTjpYH NbImmpnACIyn29jUsaVVG+dTV4/sILG9ShTPArCv+TudjK2gmw6OGFPHFwgkUn6ecvm2So 4SHBVaiqyy9oojNgoUJaw5WJPeQt+5w= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-113-Pd_58nfsNgK1vb0SKLtDeA-1; Mon, 03 Jun 2024 11:04:48 -0400 X-MC-Unique: Pd_58nfsNgK1vb0SKLtDeA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6FB973806707; Mon, 3 Jun 2024 15:04:48 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.225.103]) by smtp.corp.redhat.com (Postfix) with SMTP id E8A9F103A3B1; Mon, 3 Jun 2024 15:04:46 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 3 Jun 2024 17:03:19 +0200 (CEST) Date: Mon, 3 Jun 2024 17:03:17 +0200 From: Oleg Nesterov To: Thomas Gleixner Cc: Anna-Maria Behnsen , Frederic Weisbecker , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] tick: shift tick_nohz_switch_to_nohz() from tick_check_oneshot_change() to hrtimer_run_queues() Message-ID: <20240603150317.GB388@redhat.com> References: <20240530124203.GA26990@redhat.com> <20240602102007.GA27454@redhat.com> <87jzj6789b.ffs@tglx> <20240603134100.GA388@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240603134100.GA388@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.3 On 06/03, Oleg Nesterov wrote: > > On 06/03, Thomas Gleixner wrote: > > > > On Sun, Jun 02 2024 at 12:20, Oleg Nesterov wrote: > > > @@ -1891,8 +1891,11 @@ void hrtimer_run_queues(void) > > > * there only sets the check bit in the tick_oneshot code, > > > * otherwise we might deadlock vs. xtime_lock. > > > */ > > > - if (tick_check_oneshot_change(!hrtimer_is_hres_enabled())) { > > > - hrtimer_switch_to_hres(); > > > + if (tick_check_oneshot_change()) { > > > + if (hrtimer_is_hres_enabled()) > > > + hrtimer_switch_to_hres(); > > > + else > > > + tick_nohz_switch_to_nohz(); > > > > hrtimers have no business with tick_nohz_switch_to_nohz(), > > really. That's a strict tick/nohz specific thing. hrtimers do not care > > about NOHZ much. They care about whether they can switch to high > > resolution mode. > > OK, lets forget this patch then. > > But note that the comment above the tick_check_oneshot_change() says > "switch to highres and / or nohz mode". But yes, please forget this patch ;) Currently hrtimer_run_queues() doesn't return if tick_check_oneshot_change() itself calls tick_nohz_switch_to_nohz() and returns 0. Oleg.