From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 EAC41126C01 for ; Mon, 23 Sep 2024 15:43:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727106192; cv=none; b=eI56g3Lr/umYJFABAs5ncRnT2ro0mM6dEtvdNrVdAzF6SPORr6bNDfDHAzYcq7cJnC8QbtoOlPUv9bohdibIhS7WAEmxHU9o7c52ZDBSzId9Zh6p04LfYaofGwoP4kFrcS+aVYYpwWUxOzRboCb+50mPtv47oElgNf3tbKp8YtE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727106192; c=relaxed/simple; bh=zPyNbzcjm4grWlNm7sx45+kDDygsbik4KwyJ/2EXoEc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GDQClYvMIm4q6kmOP/lDK3/ufjus+qkxF/0vNGNmABS31QTbZjOpbHcU3tv19hNSnJRDs+7/NDykm/csUlj4pwme5VUEKnBAlFCOjwnOosUKdsosLr2RWJS7pVD0aoXXu2/tE6SbeaZqOwdcCrLc+BEv1Q4ZBGBT2J9Rm8fcBo8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dpQZDwk5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dpQZDwk5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 612F8C4CEC4; Mon, 23 Sep 2024 15:43:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1727106191; bh=zPyNbzcjm4grWlNm7sx45+kDDygsbik4KwyJ/2EXoEc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dpQZDwk5gYTHJq/Clmo/NQ0QAAhdCNLYJbJc4hDyBU8Uka2q2XPG9ZNA+ZWjTPumH 5cIjjbyJxdMhkVKw6iuR5kFAK6+FLroz0uYUFAlrG0k7qeVgc7XFpbkGvK0Z1xi93I /BpphYzeC9UH5JGPBJ7yFjnh8AMBsX1rVJm4s06eH6NjvbnYh6yZZlDg3cItXp423X hNq6OWNgwuVaFWCkl/45uF6uTmxfNtJTPGgX2wSlTDrk/YH4GCOblK7I0ugvWmDJkS 6yeGiPiBiE5hCfrNDUfCb8D/yCE3N1GoRO/Qo+HJthZAliMpX/75KpEo9YqvC12pj5 Z/gNMb6GbyYvg== Date: Mon, 23 Sep 2024 05:43:10 -1000 From: Tejun Heo To: Pat Somaru Cc: void@manifault.com, linux-kernel@vger.kernel.org, kernel-team@meta.com, sched-ext@meta.com, peterz@infradead.org Subject: Re: [PATCH sched_ext/for-6.12-fixes] Disable SM_IDLE/rq empty path when scx_enabled Message-ID: References: <20240920194159.158152-1-patso@likewhatevs.io> 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: <20240920194159.158152-1-patso@likewhatevs.io> Applied to sched_ext/for-6.12-fixes with minor edits: ------ 8< ------ >From edf1c586e92675c4e0eb27758fcdb55a56838de1 Mon Sep 17 00:00:00 2001 From: Pat Somaru Date: Fri, 20 Sep 2024 15:41:59 -0400 Subject: [PATCH] sched, sched_ext: Disable SM_IDLE/rq empty path when scx_enabled() Disable the rq empty path when scx is enabled. SCX must consult the BPF scheduler (via the dispatch path in balance) to determine if rq is empty. This fixes stalls when scx is enabled. Signed-off-by: Pat Somaru Fixes: 3dcac251b066 ("sched/core: Introduce SM_IDLE and an idle re-entry fast-path in __schedule()") Signed-off-by: Tejun Heo --- kernel/sched/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index b6cc1cf499d6..43e453ab7e20 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6591,7 +6591,8 @@ static void __sched notrace __schedule(int sched_mode) */ prev_state = READ_ONCE(prev->__state); if (sched_mode == SM_IDLE) { - if (!rq->nr_running) { + /* SCX must consult the BPF scheduler to tell if rq is empty */ + if (!rq->nr_running && !scx_enabled()) { next = prev; goto picked; } -- 2.46.0