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Fri, 13 Mar 2026 09:06:42 +0000 (GMT) Date: Fri, 13 Mar 2026 10:06:41 +0100 From: Heiko Carstens To: Harald Freudenberger Cc: lirongqing , Holger Dengler , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , linux-s390@vger.kernel.org Subject: Re: [PATCH] s390/pkey: Remove synchronize_rcu from pkey_handler_register Message-ID: <20260313090641.13729Aae-hca@linux.ibm.com> References: <20260313052312.2389-1-lirongqing@baidu.com> <058c161c4e82d2d78ddb9c52cfc8ee50@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <058c161c4e82d2d78ddb9c52cfc8ee50@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: RccSYkCGrQqFYCFugMZzYZbhqU_ginuk X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzEzMDA2OSBTYWx0ZWRfX1BGLLMmzRXzm R9xg5BU6LdA3zf5WdbRoqDATxZ54LoZsrLZZQCh6MiEQNS4r34DYT3e/5xSgNHVx+dvD//+m34L Mdfent01wWmzYK4/0Tuem0C6MB/pvUoYv/pAGofpEc80lURwi5cjV0+ZPeHId6epEBOQBbOzBOY 3VFPfpZZAK+NOrsreAxn7M+Lw/oLMP/AakmDiH1FYKZedFiQjpZTe7DiATZUWZdTNB9JLbfzfE3 02cD5OENdE5fUPxV7aegeN9OLSW49vdN6tU1TL+viBXVAuPy87PrMMJWYbi0gudVHqWYyYBu+xZ VEN5r05kQpPbgmRjec5uyIRlWAVHGK4rBGzUmGkwuha2iCFw4Q2sf0s6NuaDwGVv/Ci0v8IHY+u scGdxuNg7XiykUKOD6Yxc9Ee9rGyXwc7ObKlOLFjrMRPtFPGO+KBbKN8Jo46zitF14abkxp2Ehm lg+eziRHnrMFAmeDwEg== X-Proofpoint-GUID: RccSYkCGrQqFYCFugMZzYZbhqU_ginuk X-Authority-Analysis: v=2.4 cv=XNk9iAhE c=1 sm=1 tr=0 ts=69b3d3a8 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=kj9zAlcOel0A:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=zuLzuavZAAAA:8 a=VnNF1IyMAAAA:8 a=k6490w7z2KT0A4n5li8A:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-13_01,2026-03-12_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 adultscore=0 bulkscore=0 phishscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603130069 On Fri, Mar 13, 2026 at 09:32:39AM +0100, Harald Freudenberger wrote: > On 2026-03-13 06:23, lirongqing wrote: > > From: Li RongQing > > > > The synchronize_rcu() call after adding a handler to the handler_list > > is redundant because RCU readers will either see the old list or the > > new list. Removing this synchronization point reduces the blocking > > time during handler registration. > > > > Signed-off-by: Li RongQing > > --- > > drivers/s390/crypto/pkey_base.c | 1 - > > 1 file changed, 1 deletion(-) > > > > diff --git a/drivers/s390/crypto/pkey_base.c > > b/drivers/s390/crypto/pkey_base.c > > index d60cd98..c2e29d6 100644 > > --- a/drivers/s390/crypto/pkey_base.c > > +++ b/drivers/s390/crypto/pkey_base.c > > @@ -60,7 +60,6 @@ int pkey_handler_register(struct pkey_handler > > *handler) > > > > list_add_rcu(&handler->list, &handler_list); > > spin_unlock(&handler_list_write_lock); > > - synchronize_rcu(); > > > > module_put(handler->module); > > Thanks Li RongQing > > Reviewed-by: Harald Freudenberger With synchronize_rcu() you do know that other CPUs will see the new list after this function returned, without not. Is that ok?