From nobody Sun Apr 19 23:31:54 2026 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 AEBA4C43334 for ; Fri, 24 Jun 2022 07:43:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229885AbiFXHnA (ORCPT ); Fri, 24 Jun 2022 03:43:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35294 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229469AbiFXHm6 (ORCPT ); Fri, 24 Jun 2022 03:42:58 -0400 Received: from alexa-out.qualcomm.com (alexa-out.qualcomm.com [129.46.98.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D3128120AF for ; Fri, 24 Jun 2022 00:42:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; i=@quicinc.com; q=dns/txt; s=qcdkim; t=1656056577; x=1687592577; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=RfyrWIIDa4w9dz4gyd2U2zmHYdad2jtAHPjANf5neDw=; b=i7B5IltNEA/c4ba0NY/I4VsPf93t4cTa1w/JZ9kUKcL6XWCf+h5YU8gE n7vhQp+oZe+SKtKvde1m9h6ZPLPQnkQX7ZaN6rGvNHVq5wYHayt0/0npS 0sfnIJ2qhjB7PT+wZYvPFbyZfQzavY2KmE269Ziva7oV67JWDhtTUG38l 0=; Received: from ironmsg09-lv.qualcomm.com ([10.47.202.153]) by alexa-out.qualcomm.com with ESMTP; 24 Jun 2022 00:42:57 -0700 X-QCInternal: smtphost Received: from nasanex01c.na.qualcomm.com ([10.47.97.222]) by ironmsg09-lv.qualcomm.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Jun 2022 00:42:57 -0700 Received: from nalasex01a.na.qualcomm.com (10.47.209.196) by nasanex01c.na.qualcomm.com (10.47.97.222) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.22; Fri, 24 Jun 2022 00:42:56 -0700 Received: from hu-satyap-lv.qualcomm.com (10.49.16.6) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.22; Fri, 24 Jun 2022 00:42:56 -0700 From: Satya Durga Srinivasu Prabhala To: , , , , , , , , , CC: Satya Durga Srinivasu Prabhala , Subject: [PATCH] sched: fix rq lock recursion issue Date: Fri, 24 Jun 2022 00:42:40 -0700 Message-ID: <20220624074240.13108-1-quic_satyap@quicinc.com> X-Mailer: git-send-email 2.36.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.49.16.6] X-ClientProxiedBy: nalasex01b.na.qualcomm.com (10.47.209.197) To nalasex01a.na.qualcomm.com (10.47.209.196) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Below recursion is observed in a rare scenario where __schedule() takes rq lock, at around same time task's affinity is being changed, bpf function for tracing sched_switch calls migrate_enabled(), checks for affinity change (cpus_ptr !=3D cpus_mask) lands into __set_cpus_allowed_ptr which tries acquire rq lock and causing the recursion bug. Fix the issue by switching to preempt_enable/disable() for non-RT Kernels. -010 |spin_bug(lock =3D ???, msg =3D ???) -011 |debug_spin_lock_before(inline) -011 |do_raw_spin_lock(lock =3D 0xFFFFFF89323BB600) -012 |_raw_spin_lock(inline) -012 |raw_spin_rq_lock_nested(inline) -012 |raw_spin_rq_lock(inline) -012 |task_rq_lock(p =3D 0xFFFFFF88CFF1DA00, rf =3D 0xFFFFFFC03707BBE8) -013 |__set_cpus_allowed_ptr(inline) -013 |migrate_enable() -014 |trace_call_bpf(call =3D ?, ctx =3D 0xFFFFFFFDEF954600) -015 |perf_trace_run_bpf_submit(inline) -015 |perf_trace_sched_switch(__data =3D 0xFFFFFFE82CF0BCB8, preempt =3D FA= LSE, prev =3D ?, next =3D ?) -016 |__traceiter_sched_switch(inline) -016 |trace_sched_switch(inline) -016 |__schedule(sched_mode =3D ?) -017 |schedule() -018 |arch_local_save_flags(inline) -018 |arch_irqs_disabled(inline) -018 |__raw_spin_lock_irq(inline) -018 |_raw_spin_lock_irq(inline) -018 |worker_thread(__worker =3D 0xFFFFFF88CE251300) -019 |kthread(_create =3D 0xFFFFFF88730A5A80) -020 |ret_from_fork(asm) Signed-off-by: Satya Durga Srinivasu Prabhala --- kernel/sched/core.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index bfa7452ca92e..e254e9227341 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2223,6 +2223,7 @@ static void migrate_disable_switch(struct rq *rq, str= uct task_struct *p) =20 void migrate_disable(void) { +#ifdef CONFIG_PREEMPT_RT struct task_struct *p =3D current; =20 if (p->migration_disabled) { @@ -2234,11 +2235,15 @@ void migrate_disable(void) this_rq()->nr_pinned++; p->migration_disabled =3D 1; preempt_enable(); +#else + preempt_disable(); +#endif } EXPORT_SYMBOL_GPL(migrate_disable); =20 void migrate_enable(void) { +#ifdef CONFIG_PREEMPT_RT struct task_struct *p =3D current; =20 if (p->migration_disabled > 1) { @@ -2265,6 +2270,9 @@ void migrate_enable(void) p->migration_disabled =3D 0; this_rq()->nr_pinned--; preempt_enable(); +#else + preempt_enable(); +#endif } EXPORT_SYMBOL_GPL(migrate_enable); =20 --=20 2.36.1