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 X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A3E03C433DF for ; Mon, 8 Jun 2020 23:38:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7CB6C2068D for ; Mon, 8 Jun 2020 23:38:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591659523; bh=Uw9/vRLVgKmqGjw40c38O9e7lpuxn5NHt5DzieU+7Dk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ivMH3OqmmRbUamEMGCkb8bubYpxJStTvl//jwQNOVjx5IG7zJYfSPnO7qsZxi1WG1 k5Jn+2mog1F9/oKS3a14jSPyY8494B6Nmm5eSO3bjvf4OfWG840ZhS9XGHHykiitBj sKMu3uGTTxznvfbBWwyTqWpTpGjI9pOHngG1ZnDc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387616AbgFHXim (ORCPT ); Mon, 8 Jun 2020 19:38:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:57838 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732216AbgFHX2Y (ORCPT ); Mon, 8 Jun 2020 19:28:24 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EA48420897; Mon, 8 Jun 2020 23:28:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591658903; bh=Uw9/vRLVgKmqGjw40c38O9e7lpuxn5NHt5DzieU+7Dk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HQJZDW4CB0zAOxjR1p6MjK+Qj+l7ecLfh7JGxBqSCt2U5gLUWO3D0X/0dAq9WqnKJ 5UVXwkTFiTc+nzEl+nU/TPTK+pY/m/M4FxAjGj/hIu+i4sxxaJis7g+BMBLrLzDdHj UJJ/L7/zidNqNMTbRLmtFcZbmuT6bdSqTVdwY6B8= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Daniel Thompson , Will Deacon , Douglas Anderson , Sasha Levin , kgdb-bugreport@lists.sourceforge.net Subject: [PATCH AUTOSEL 4.4 24/37] kgdb: Fix spurious true from in_dbg_master() Date: Mon, 8 Jun 2020 19:27:36 -0400 Message-Id: <20200608232750.3370747-24-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200608232750.3370747-1-sashal@kernel.org> References: <20200608232750.3370747-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Daniel Thompson [ Upstream commit 3fec4aecb311995189217e64d725cfe84a568de3 ] Currently there is a small window where a badly timed migration could cause in_dbg_master() to spuriously return true. Specifically if we migrate to a new core after reading the processor id and the previous core takes a breakpoint then we will evaluate true if we read kgdb_active before we get the IPI to bring us to halt. Fix this by checking irqs_disabled() first. Interrupts are always disabled when we are executing the kgdb trap so this is an acceptable prerequisite. This also allows us to replace raw_smp_processor_id() with smp_processor_id() since the short circuit logic will prevent warnings from PREEMPT_DEBUG. Fixes: dcc7871128e9 ("kgdb: core changes to support kdb") Suggested-by: Will Deacon Link: https://lore.kernel.org/r/20200506164223.2875760-1-daniel.thompson@linaro.org Reviewed-by: Douglas Anderson Signed-off-by: Daniel Thompson Signed-off-by: Sasha Levin --- include/linux/kgdb.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h index e465bb15912d..6be5545d3584 100644 --- a/include/linux/kgdb.h +++ b/include/linux/kgdb.h @@ -317,7 +317,7 @@ extern void gdbstub_exit(int status); extern int kgdb_single_step; extern atomic_t kgdb_active; #define in_dbg_master() \ - (raw_smp_processor_id() == atomic_read(&kgdb_active)) + (irqs_disabled() && (smp_processor_id() == atomic_read(&kgdb_active))) extern bool dbg_is_early; extern void __init dbg_late_init(void); #else /* ! CONFIG_KGDB */ -- 2.25.1