From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 B57A22E62B3; Fri, 28 Nov 2025 10:57:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764327454; cv=none; b=P3mY6lnJAFQ2IeEYk4qZ7b2YJMypgUuyDoSdmvjgh1Ff2pCDhCgH6MZaRZHzS5YZxqjWJ9kQLz2tPEc4SOCPUMmilSkVEDZUF+bzBIFaSls/uLEe2hPJK//h5wFvl0wemmoL2m5z+q/cI5zjCTGQhnP9EgWLD5FtP09ldQ0fIPo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764327454; c=relaxed/simple; bh=WTYR0RscpSvi0Bh+i64GZQJOUOmjlo6lTUqznrkqlv0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=detK44GTLcMembf/8vf1OSyJgl+nulF2zO7qRKa0uBiS7A56l86JXEO3glI0KZIk2ltVxRf24AUIpIy/eabS4wNURRZU7/JAZOwfshOHJg1PqjWoTQF4GFajj6gAHnocLVx/PdJyQiMFvZGJbh9VFnkgl3F2rNq4npfyP+MQLag= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=cjoHfjJu; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="cjoHfjJu" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=4BcQtPtVsVxAJWT0qW2w0lTC/fZLWNffzIs+i+oQZ4k=; b=cjoHfjJuQwvyeIRpUHHAr6ld8m aTXzMydrtiMYDS/FilWyhOebMDZXysmkAjIQfe5vD0yXajrrrsvQlugdCssR1wHbkzVOnsLjR9jFp EZp96z/kbJbywRt0k1xWnP9liV7H3zWGvAylYfOQg1ALSF2DxCF9DUh0OdYar/8PN7NHf7kIV4dVn o4wwtxgELQbBH5CD3eWB61VT0VfsHibNFK4IMFxATT41FfqUy/vlP85HMOJjIuLRt8m+uHWUC3p+P rtk5t+Z/D2o6lOeNUG/Gw7e/700keA25Wd+VffHGnJqZoAAaFh0kR+dsAE62Fjyx9vXWHTUDS6eaT xtUHeBjw==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1vOvIg-0000000BlG0-49yt; Fri, 28 Nov 2025 10:02:03 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 6E2A2300230; Fri, 28 Nov 2025 11:57:23 +0100 (CET) Date: Fri, 28 Nov 2025 11:57:23 +0100 From: Peter Zijlstra To: mingo@kernel.org, vincent.guittot@linaro.org Cc: linux-kernel@vger.kernel.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, tj@kernel.org, void@manifault.com, arighi@nvidia.com, changwoo@igalia.com, sched-ext@lists.linux.dev Subject: Re: [PATCH 3/5] sched: Change rcu_dereference_check_sched_domain() to rcu-sched Message-ID: <20251128105723.GZ4067720@noisy.programming.kicks-ass.net> References: <20251127153943.696191429@infradead.org> <20251127154725.647502625@infradead.org> Precedence: bulk X-Mailing-List: sched-ext@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251127154725.647502625@infradead.org> On Thu, Nov 27, 2025 at 04:39:46PM +0100, Peter Zijlstra wrote: > By changing rcu_dereference_check_sched_domain() to use > rcu_dereference_sched_check() it also considers preempt_disable() to > be equivalent to rcu_read_lock(). > > Since rcu fully implies rcu_sched this has absolutely no change in > behaviour, but it does allow removing a bunch of otherwise redundant > rcu_read_lock() noise. This goes sideways with NUMABALANCING=y, it needs a little more. I'll have a poke.