From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:40710 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726730AbgKAQGM (ORCPT ); Sun, 1 Nov 2020 11:06:12 -0500 Date: Sun, 1 Nov 2020 17:05:54 +0100 From: Heiko Carstens Subject: Re: [PATCH] s390/smp: Move rcu_cpu_starting() earlier Message-ID: <20201101160554.GA9375@osiris> References: <20201028182742.13773-1-cai@redhat.com> <20201031183725.GA9529@osiris> <1f0ef4b832c67dcec1bcc793407e62c58a97904e.camel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1f0ef4b832c67dcec1bcc793407e62c58a97904e.camel@redhat.com> List-ID: To: Qian Cai Cc: "Paul E. McKenney" , Peter Zijlstra , Vasily Gorbik , Christian Borntraeger , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org On Sat, Oct 31, 2020 at 07:38:52PM -0400, Qian Cai wrote: > > > This is avoided by moving the call to rcu_cpu_starting up near the > > > beginning of the smp_init_secondary() function. Note that the > > > raw_smp_processor_id() is required in order to avoid calling into > > > lockdep before RCU has declared the CPU to be watched for readers. > > > > > > Link: https://lore.kernel.org/lkml/160223032121.7002.1269740091547117869.tip-bot2@tip-bot2/ > > > Signed-off-by: Qian Cai > > > --- > > > arch/s390/kernel/smp.c | 3 ++- > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > Could you provide the config you used? I'm wondering why I can't > > reproduce this even though I have lot's of debug options enabled. > https://cailca.coding.net/public/linux/mm/git/files/master/s390.config > > Essentially, I believe it requires CONFIG_PROVE_RCU_LIST=y. Also, it occurs to > me that this only starts to happen after the commit mentioned in the above link. Yes, with that enabled I can reprocuce it. Thanks! It depends on CONFIG_RCU_EXPERT. I can't image why I didn't had that enabled.. :)