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 F119DC3F6B0 for ; Sun, 7 Aug 2022 15:39:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234605AbiHGPjF (ORCPT ); Sun, 7 Aug 2022 11:39:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44706 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233356AbiHGPjE (ORCPT ); Sun, 7 Aug 2022 11:39:04 -0400 Received: from fanzine2.igalia.com (fanzine.igalia.com [178.60.130.6]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 14D4A626B; Sun, 7 Aug 2022 08:39:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From: References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=FfOmDqrueH5zbkn3yATMhpqMWWEe+35EmBPi72/LV0I=; b=qAULYagpbd2RoWJByTE0dULDjL r7Tu7V5xMI6abRrlBB1Hdw79O2+Gi1+SniR1hAmkwGAZLtm63NGffvzeN9UTGCm5bw4JRv7N3/vug hf4eGxeOAY49HIsm/Vot9pTpSQF7Q8xM6I2Rt5rEoIcAvOGE8ciejoIAfsZ/B2IsWvr82U8P7Hk4Q C13RHqD5sFxOCSCBo5zBx6YZ1ZD36P7qDjBwFgNMsZ2OSQ7nnkn9tW6FLa5TptfpHKGEa0NR0w1Z+ k8DeFu3wlxquxk0Jsn7hIHZjWq2TmYaGFvCrd1/xXk1jUKgyliHRhTH6USSKsazGe0o59QY0IFDhP FxNVrtnQ==; Received: from [187.56.70.103] (helo=[192.168.1.60]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1oKiMm-0011kP-W9; Sun, 07 Aug 2022 17:39:01 +0200 Message-ID: <5e9d4906-3601-f07d-a886-7a723c6867c8@igalia.com> Date: Sun, 7 Aug 2022 12:38:33 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v2 03/13] firmware: google: Test spinlock on panic path to avoid lockups Content-Language: en-US To: kexec@lists.infradead.org, linux-efi@vger.kernel.org, Evan Green Cc: pmladek@suse.com, bhe@redhat.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, netdev@vger.kernel.org, x86@kernel.org, kernel-dev@igalia.com, kernel@gpiccoli.net, halves@canonical.com, fabiomirmar@gmail.com, alejandro.j.jimenez@oracle.com, andriy.shevchenko@linux.intel.com, arnd@arndb.de, bp@alien8.de, corbet@lwn.net, d.hatayama@jp.fujitsu.com, dave.hansen@linux.intel.com, dyoung@redhat.com, feng.tang@intel.com, gregkh@linuxfoundation.org, mikelley@microsoft.com, hidehiro.kawai.ez@hitachi.com, jgross@suse.com, john.ogness@linutronix.de, keescook@chromium.org, luto@kernel.org, mhiramat@kernel.org, mingo@redhat.com, paulmck@kernel.org, peterz@infradead.org, rostedt@goodmis.org, senozhatsky@chromium.org, stern@rowland.harvard.edu, tglx@linutronix.de, vgoyal@redhat.com, vkuznets@redhat.com, will@kernel.org, Ard Biesheuvel , Julius Werner , David Gow References: <20220719195325.402745-1-gpiccoli@igalia.com> <20220719195325.402745-4-gpiccoli@igalia.com> From: "Guilherme G. Piccoli" In-Reply-To: <20220719195325.402745-4-gpiccoli@igalia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On 19/07/2022 16:53, Guilherme G. Piccoli wrote: > Currently the gsmi driver registers a panic notifier as well as > reboot and die notifiers. The callbacks registered are called in > atomic and very limited context - for instance, panic disables > preemption and local IRQs, also all secondary CPUs (not executing > the panic path) are shutdown. > > With that said, taking a spinlock in this scenario is a dangerous > invitation for lockup scenarios. So, fix that by checking if the > spinlock is free to acquire in the panic notifier callback - if not, > bail-out and avoid a potential hang. > > Fixes: 74c5b31c6618 ("driver: Google EFI SMI") > Cc: Ard Biesheuvel > Cc: David Gow > Cc: Evan Green > Cc: Julius Werner > Signed-off-by: Guilherme G. Piccoli > > --- > > V2: > - do not use spin_trylock anymore, to avoid messing with > non-panic paths; now we just check the spinlock state in > the panic notifier before taking it. Thanks Evan for the > review/idea! > > drivers/firmware/google/gsmi.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > [...] Hi Evan, do you think this one is good now, based on your previous review? Appreciate any feedback! Cheers, Guilherme