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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 4D07EECDE47 for ; Thu, 8 Nov 2018 17:14:35 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8388D20817 for ; Thu, 8 Nov 2018 17:14:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8388D20817 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=debian.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 42rVJS3BB9zF3SB for ; Fri, 9 Nov 2018 04:14:32 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=debian.org Authentication-Results: lists.ozlabs.org; spf=none (mailfrom) smtp.mailfrom=debian.org (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=leitao@debian.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=debian.org Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 42rVGR2zL7zF3Qx for ; Fri, 9 Nov 2018 04:12:47 +1100 (AEDT) Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wA8H9g0c019459 for ; Thu, 8 Nov 2018 12:12:44 -0500 Received: from e31.co.us.ibm.com (e31.co.us.ibm.com [32.97.110.149]) by mx0a-001b2d01.pphosted.com with ESMTP id 2nms56rpks-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 08 Nov 2018 12:12:44 -0500 Received: from localhost by e31.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 8 Nov 2018 17:12:41 -0000 Received: from b03ledav006.gho.boulder.ibm.com (b03ledav006.gho.boulder.ibm.com [9.17.130.237]) by b03cxnp08028.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id wA8HCeq119529898 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 8 Nov 2018 17:12:40 GMT Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 860BAC605F; Thu, 8 Nov 2018 17:12:40 +0000 (GMT) Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E1B78C6057; Thu, 8 Nov 2018 17:12:39 +0000 (GMT) Received: from debra.ibm.com (unknown [9.18.239.97]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTP; Thu, 8 Nov 2018 17:12:39 +0000 (GMT) From: Breno Leitao To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH] powerpc/xmon: Fix invocation inside lock region Date: Thu, 8 Nov 2018 15:12:42 -0200 X-Mailer: git-send-email 1.8.3.1 X-TM-AS-GCONF: 00 x-cbid: 18110817-8235-0000-0000-00000E238ACA X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010008; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000269; SDB=6.01114532; UDB=6.00577840; IPR=6.00894631; MB=3.00024076; MTD=3.00000008; XFM=3.00000015; UTC=2018-11-08 17:12:42 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18110817-8236-0000-0000-00004349796A Message-Id: <1541697162-1926-1-git-send-email-leitao@debian.org> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2018-11-08_08:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=414 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1811080145 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Breno Leitao Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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 --- 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; -- 2.19.0