From nobody Sun Sep 14 16:23:33 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CB95AC05027 for ; Fri, 20 Jan 2023 15:04:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231263AbjATPEj (ORCPT ); Fri, 20 Jan 2023 10:04:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38520 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230429AbjATPEa (ORCPT ); Fri, 20 Jan 2023 10:04:30 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 80FDB81013 for ; Fri, 20 Jan 2023 07:03:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674227022; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=F1TJWHWdZqDFCr8xEA0m937H+WTiVZmJanYCSnQgjrk=; b=aBw3t80SCMtSlaTEoenyoVBHtZz+Vxk9rFf7DH2Lv66xzogqsM5cjEBtW+rvh1kRa1g1LR 3rOuEySgjIG/wSgvGemc1SpdTW3z11BQLYtsXZdkRlN+T3LwK7Tktmb7AINbZ8PTqkPohB i9grLRDACUvJucBwrv1JbVJf9ZE8RmM= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-16-XksM0rtCN-K57tGpGanOQQ-1; Fri, 20 Jan 2023 10:03:35 -0500 X-MC-Unique: XksM0rtCN-K57tGpGanOQQ-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 18E4F181E3EE; Fri, 20 Jan 2023 15:03:34 +0000 (UTC) Received: from fedora.redhat.com (unknown [10.22.32.187]) by smtp.corp.redhat.com (Postfix) with ESMTP id 44B13492B02; Fri, 20 Jan 2023 15:03:29 +0000 (UTC) From: Wander Lairson Costa To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , "Eric W. Biederman" , Stafford Horne , Guo Ren , Kefeng Wang , Oleg Nesterov , Wander Lairson Costa , Andrew Morton , Thomas Gleixner , Sebastian Andrzej Siewior , Andy Lutomirski , "Liam R. Howlett" , Fenghua Yu , Andrei Vagin , linux-kernel@vger.kernel.org (open list) Subject: [PATCH v2 3/4] sched/rt: use put_task_struct_atomic_safe() to avoid potential splat Date: Fri, 20 Jan 2023 12:02:41 -0300 Message-Id: <20230120150246.20797-4-wander@redhat.com> In-Reply-To: <20230120150246.20797-1-wander@redhat.com> References: <20230120150246.20797-1-wander@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" rto_push_irq_work_func() is called in hardirq context, and it calls push_rt_task(), which calls put_task_struct(). If the kernel is compiled with PREEMPT_RT and put_task_struct() reaches zero usage count, it triggers a splat because __put_task_struct() indirectly acquires sleeping locks. The put_task_struct() call pairs with an earlier get_task_struct(), which makes the probability of the usage count reaches zero pretty low. In any case, let's play safe and use the atomic safe version. Signed-off-by: Wander Lairson Costa Cc: Thomas Gleixner Reviewed-by: Steven Rostedt (Google) --- kernel/sched/rt.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index ed2a47e4ddae..30a4e9607bec 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2147,7 +2147,7 @@ static int push_rt_task(struct rq *rq, bool pull) /* * Something has shifted, try again. */ - put_task_struct(next_task); + put_task_struct_atomic_safe(next_task); next_task =3D task; goto retry; } @@ -2160,7 +2160,7 @@ static int push_rt_task(struct rq *rq, bool pull) =20 double_unlock_balance(rq, lowest_rq); out: - put_task_struct(next_task); + put_task_struct_atomic_safe(next_task); =20 return ret; } --=20 2.39.0