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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 11 Apr 2019 04:23:14 +0100 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x3B3NDVr18481342 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 11 Apr 2019 03:23:13 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 050E34C04E; Thu, 11 Apr 2019 03:23:13 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 426074C04A; Thu, 11 Apr 2019 03:23:12 +0000 (GMT) Received: from [9.124.31.167] (unknown [9.124.31.167]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 11 Apr 2019 03:23:12 +0000 (GMT) Subject: Re: [PATCH v2] powerpc/watchdog: Use hrtimers for per-CPU heartbeat To: Nicholas Piggin References: <20190409044005.26446-1-npiggin@gmail.com> From: Ravi Bangoria Date: Thu, 11 Apr 2019 08:53:11 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190409044005.26446-1-npiggin@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19041103-0016-0000-0000-0000026D8E21 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19041103-0017-0000-0000-000032C9C070 Message-Id: <558e8f44-ff88-76c3-4f9a-72c3157a9234@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-04-11_02:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=877 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904110023 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: "Gautham R . Shenoy" , Ravikumar Bangoria , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 4/9/19 10:10 AM, Nicholas Piggin wrote: > Using a jiffies timer creates a dependency on the tick_do_timer_cpu > incrementing jiffies. If that CPU has locked up and jiffies is not > incrementing, the watchdog heartbeat timer for all CPUs stops and > creates false positives and confusing warnings on local CPUs, and > also causes the SMP detector to stop, so the root cause is never > detected. > > Fix this by using hrtimer based timers for the watchdog heartbeat, > like the generic kernel hardlockup detector. > > Cc: Gautham R. Shenoy > Reported-by: Ravikumar Bangoria > Signed-off-by: Nicholas Piggin This one is giving me a proper backtrace when hardlockup happens with perf_fuzzer so, Tested-by: Ravi Bangoria Neat: Reported-by: Ravi Bangoria