From mboxrd@z Thu Jan 1 00:00:00 1970 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 9FCFDC4332F for ; Thu, 24 Nov 2022 05:23:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229473AbiKXFXW (ORCPT ); Thu, 24 Nov 2022 00:23:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44516 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229436AbiKXFXV (ORCPT ); Thu, 24 Nov 2022 00:23:21 -0500 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1560B58BC3 for ; Wed, 23 Nov 2022 21:23:20 -0800 (PST) Received: from linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net (linux.microsoft.com [13.77.154.182]) by linux.microsoft.com (Postfix) with ESMTPSA id 5EC2320B83C2; Wed, 23 Nov 2022 21:23:19 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 5EC2320B83C2 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1669267399; bh=MVfZuNzlk/Ta9CdVuPwvvYAZ+M9TwSSSa0WsZCzXMUY=; h=From:To:Cc:Subject:Date:From; b=cGLo1l6L0J4YdYKz5xljd2OPjhDbTT4fTZFsrG1t8kapcSYwlkJTY11m+oNpsctQE Sve+RqutHXsy+b12+psgf6ffIsYhBWtqvZ48DjijaLSbVhkRlhfmg6jdd6L1BvnxnZ /WKcbQg+FMZ8zSamDSFctQwUJSpsjizXOQ7XIZG0= From: Gaurav Kohli To: kys@microsoft.com, decui@microsoft.com, haiyangz@microsoft.com, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, linux-hyperv@vger.kernel.org, wei.liu@kernel.org, bp@alien8.de Cc: gauravkohli@linux.microsoft.com Subject: [PATCH] x86/hyperv: Remove unregister syscore call from hyperv cleanup Date: Wed, 23 Nov 2022 21:23:11 -0800 Message-Id: <1669267391-9809-1-git-send-email-gauravkohli@linux.microsoft.com> X-Mailer: git-send-email 1.8.3.1 Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org Hyperv cleanup codes comes under panic path where preemption and irq is already disabled. So calling of unregister_syscore_ops which has mutex from hyperv cleanup might schedule out the thread and never comes back. To prevent the same remove unwanted unregister_syscore_ops function call. Signed-off-by: Gaurav Kohli diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c index f49bc3ec76e6..c050de69dfde 100644 --- a/arch/x86/hyperv/hv_init.c +++ b/arch/x86/hyperv/hv_init.c @@ -537,7 +537,12 @@ void hyperv_cleanup(void) union hv_x64_msr_hypercall_contents hypercall_msr; union hv_reference_tsc_msr tsc_msr; - unregister_syscore_ops(&hv_syscore_ops); + /* + * Avoid unregister_syscore_ops(&hv_syscore_ops) from cleanup code, + * as this is only called in crash path where irq and preemption disabled. + * If we add this, there is a chance that this get scheduled out due to mutex + * in unregister_syscore_ops and never comes back. + */ /* Reset our OS id */ wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0); -- 2.17.1