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McKenney" , Peter Zijlstra , Vasily Gorbik , Christian Borntraeger , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org 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> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-01_05:2020-10-30,2020-11-01 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=984 phishscore=0 spamscore=0 mlxscore=0 clxscore=1015 suspectscore=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 adultscore=0 bulkscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011010130 Precedence: bulk List-ID: X-Mailing-List: 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.. :)