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,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 7E222C282C3 for ; Thu, 24 Jan 2019 19:49:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4CFC021726 for ; Thu, 24 Jan 2019 19:49:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548359364; bh=9a0qO9Ky99wSTSAEUP40P7ejU76lDOiRjKbGW+KvEtg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=VL3ud4XlAeVeIa7DhDgRzpYle7Crnn2f17pb3R10FOmcSSLODcWVcc7HRiCeDJ+u2 SaiIhzYDNstyQsU/fbe+6HqAOKHNixspqU53UV6Kasyzi9BV2ySzp3zb8w4qeL4pSB KkVdxPckpWFjAFYQjQ3iVdpsIeHWcz568r05XZlY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387550AbfAXTlO (ORCPT ); Thu, 24 Jan 2019 14:41:14 -0500 Received: from mail.kernel.org ([198.145.29.99]:41500 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732766AbfAXTlN (ORCPT ); Thu, 24 Jan 2019 14:41:13 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2B47220663; Thu, 24 Jan 2019 19:41:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548358872; bh=9a0qO9Ky99wSTSAEUP40P7ejU76lDOiRjKbGW+KvEtg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vMriZwM5GEkmWdzTzi4u57JvEo55uUilaT77PBtOjOhPP5UacYKliFfhGuAq/H2ze bOfOHUUnThvzxRBOG3ZoqWSEYkcXbScXBlA1ut06w+Xy5RSp0UYYhmRknZw4mhvC0M BnULXDnODBjFq4FVlvzrabjmSs4F927OGHRZPZZQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Breno Leitao , Thiago Jung Bauermann , Michael Ellerman , Sasha Levin Subject: [PATCH 4.20 056/127] powerpc/xmon: Fix invocation inside lock region Date: Thu, 24 Jan 2019 20:20:02 +0100 Message-Id: <20190124190214.576622787@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190124190211.984305387@linuxfoundation.org> References: <20190124190211.984305387@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 4.20-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit 8d4a862276a9c30a269d368d324fb56529e6d5fd ] Currently xmon needs to get devtree_lock (through rtas_token()) during its invocation (at crash time). If there is a crash while devtree_lock is being held, then xmon tries to get the lock but spins forever and never get into the interactive debugger, as in the following case: int *ptr = NULL; raw_spin_lock_irqsave(&devtree_lock, flags); *ptr = 0xdeadbeef; This patch avoids calling rtas_token(), thus trying to get the same lock, at crash time. This new mechanism proposes getting the token at initialization time (xmon_init()) and just consuming it at crash time. This would allow xmon to be possible invoked independent of devtree_lock being held or not. Signed-off-by: Breno Leitao Reviewed-by: Thiago Jung Bauermann Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin --- arch/powerpc/xmon/xmon.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index 36b8dc47a3c3..b566203d09c5 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -75,6 +75,9 @@ static int xmon_gate; #define xmon_owner 0 #endif /* CONFIG_SMP */ +#ifdef CONFIG_PPC_PSERIES +static int set_indicator_token = RTAS_UNKNOWN_SERVICE; +#endif static unsigned long in_xmon __read_mostly = 0; static int xmon_on = IS_ENABLED(CONFIG_XMON_DEFAULT); @@ -358,7 +361,6 @@ static inline void disable_surveillance(void) #ifdef CONFIG_PPC_PSERIES /* Since this can't be a module, args should end up below 4GB. */ static struct rtas_args args; - int token; /* * At this point we have got all the cpus we can into @@ -367,11 +369,11 @@ static inline void disable_surveillance(void) * If we did try to take rtas.lock there would be a * real possibility of deadlock. */ - token = rtas_token("set-indicator"); - if (token == RTAS_UNKNOWN_SERVICE) + if (set_indicator_token == RTAS_UNKNOWN_SERVICE) return; - rtas_call_unlocked(&args, token, 3, 1, NULL, SURVEILLANCE_TOKEN, 0, 0); + rtas_call_unlocked(&args, set_indicator_token, 3, 1, NULL, + SURVEILLANCE_TOKEN, 0, 0); #endif /* CONFIG_PPC_PSERIES */ } @@ -3688,6 +3690,14 @@ static void xmon_init(int enable) __debugger_iabr_match = xmon_iabr_match; __debugger_break_match = xmon_break_match; __debugger_fault_handler = xmon_fault_handler; + +#ifdef CONFIG_PPC_PSERIES + /* + * Get the token here to avoid trying to get a lock + * during the crash, causing a deadlock. + */ + set_indicator_token = rtas_token("set-indicator"); +#endif } else { __debugger = NULL; __debugger_ipi = NULL; -- 2.19.1