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charset="us-ascii"; Format="flowed" Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org Hello Michael, On 01/08/24 08:04, Michael Ellerman wrote: > Sourabh Jain writes: >> The following errors are observed when kexec is done with SMT=off on >> powerpc. >> >> [ 358.458385] Removing IBM Power 842 compression device >> [ 374.795734] kexec_core: Starting new kernel >> [ 374.795748] kexec: Waking offline cpu 1. >> [ 374.875695] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate >> [ 374.935833] kexec: Waking offline cpu 2. >> [ 375.015664] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate >> snip.. >> [ 375.515823] kexec: Waking offline cpu 6. >> [ 375.635667] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate >> [ 375.695836] kexec: Waking offline cpu 7. > Are they actually errors though? Do they block the actual kexec from > happening? Or are they just warnings in dmesg? The kexec kernel boots fine. This warning appears regardless of whether the kdump kernel is loaded. However, when the kdump kernel is loaded, we will not be able to update the kdump image (FDT). I think this should be fine given that kexec is in progress. Please let me know your opinion. > Because the fix looks like it could be racy. It seems like it is racy, but given that kexec takes the lock first and then brings the CPU up, which triggers the kdump image, which always fails to update the kdump image because it could not take the same lock. Note: the kexec lock is not released unless kexec boot fails. Thanks, Sourabh Jain _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6B2AFC3DA4A for ; Thu, 1 Aug 2024 06:52:10 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=aWMR8Efe; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4WZKQK0dshz3ck2 for ; Thu, 1 Aug 2024 16:52:09 +1000 (AEST) Authentication-Results: lists.ozlabs.org; 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Thu, 1 Aug 2024 06:51:07 +0000 (GMT) Message-ID: <10c666ae-d528-4f49-82e9-8e0fee7099e0@linux.ibm.com> Date: Thu, 1 Aug 2024 12:21:06 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] kexec/crash: no crash update when kexec in progress To: Michael Ellerman , bhe@redhat.com References: <20240731152738.194893-1-sourabhjain@linux.ibm.com> <87v80lnf8d.fsf@mail.lhotse> Content-Language: en-US From: Sourabh Jain In-Reply-To: <87v80lnf8d.fsf@mail.lhotse> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: zZtioG-S0Int-6TxCosUtQhJal0tsM59 X-Proofpoint-ORIG-GUID: xJ8T4tsuDp-ESR4KmDd7rzqItiiBVLcW X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-08-01_03,2024-07-31_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 spamscore=0 impostorscore=0 suspectscore=0 mlxlogscore=999 mlxscore=0 clxscore=1015 bulkscore=0 priorityscore=1501 malwarescore=0 lowpriorityscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2407110000 definitions=main-2408010035 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: x86@kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Sachin P Bappalige , linuxppc-dev@lists.ozlabs.org, Hari Bathini Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hello Michael, On 01/08/24 08:04, Michael Ellerman wrote: > Sourabh Jain writes: >> The following errors are observed when kexec is done with SMT=off on >> powerpc. >> >> [ 358.458385] Removing IBM Power 842 compression device >> [ 374.795734] kexec_core: Starting new kernel >> [ 374.795748] kexec: Waking offline cpu 1. >> [ 374.875695] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate >> [ 374.935833] kexec: Waking offline cpu 2. >> [ 375.015664] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate >> snip.. >> [ 375.515823] kexec: Waking offline cpu 6. >> [ 375.635667] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate >> [ 375.695836] kexec: Waking offline cpu 7. > Are they actually errors though? Do they block the actual kexec from > happening? Or are they just warnings in dmesg? The kexec kernel boots fine. This warning appears regardless of whether the kdump kernel is loaded. However, when the kdump kernel is loaded, we will not be able to update the kdump image (FDT). I think this should be fine given that kexec is in progress. Please let me know your opinion. > Because the fix looks like it could be racy. It seems like it is racy, but given that kexec takes the lock first and then brings the CPU up, which triggers the kdump image, which always fails to update the kdump image because it could not take the same lock. Note: the kexec lock is not released unless kexec boot fails. 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Thu, 1 Aug 2024 06:51:11 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A085D20043; Thu, 1 Aug 2024 06:51:09 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 789A320040; Thu, 1 Aug 2024 06:51:07 +0000 (GMT) Received: from [9.43.79.112] (unknown [9.43.79.112]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 1 Aug 2024 06:51:07 +0000 (GMT) Message-ID: <10c666ae-d528-4f49-82e9-8e0fee7099e0@linux.ibm.com> Date: Thu, 1 Aug 2024 12:21:06 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] kexec/crash: no crash update when kexec in progress To: Michael Ellerman , bhe@redhat.com Cc: Hari Bathini , kexec@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, x86@kernel.org, Sachin P Bappalige References: <20240731152738.194893-1-sourabhjain@linux.ibm.com> <87v80lnf8d.fsf@mail.lhotse> Content-Language: en-US From: Sourabh Jain In-Reply-To: <87v80lnf8d.fsf@mail.lhotse> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: zZtioG-S0Int-6TxCosUtQhJal0tsM59 X-Proofpoint-ORIG-GUID: xJ8T4tsuDp-ESR4KmDd7rzqItiiBVLcW X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-08-01_03,2024-07-31_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 spamscore=0 impostorscore=0 suspectscore=0 mlxlogscore=999 mlxscore=0 clxscore=1015 bulkscore=0 priorityscore=1501 malwarescore=0 lowpriorityscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2407110000 definitions=main-2408010035 Hello Michael, On 01/08/24 08:04, Michael Ellerman wrote: > Sourabh Jain writes: >> The following errors are observed when kexec is done with SMT=off on >> powerpc. >> >> [ 358.458385] Removing IBM Power 842 compression device >> [ 374.795734] kexec_core: Starting new kernel >> [ 374.795748] kexec: Waking offline cpu 1. >> [ 374.875695] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate >> [ 374.935833] kexec: Waking offline cpu 2. >> [ 375.015664] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate >> snip.. >> [ 375.515823] kexec: Waking offline cpu 6. >> [ 375.635667] crash hp: kexec_trylock() failed, elfcorehdr may be inaccurate >> [ 375.695836] kexec: Waking offline cpu 7. > Are they actually errors though? Do they block the actual kexec from > happening? Or are they just warnings in dmesg? The kexec kernel boots fine. This warning appears regardless of whether the kdump kernel is loaded. However, when the kdump kernel is loaded, we will not be able to update the kdump image (FDT). I think this should be fine given that kexec is in progress. Please let me know your opinion. > Because the fix looks like it could be racy. It seems like it is racy, but given that kexec takes the lock first and then brings the CPU up, which triggers the kdump image, which always fails to update the kdump image because it could not take the same lock. Note: the kexec lock is not released unless kexec boot fails. Thanks, Sourabh Jain