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Wed, 6 Dec 2023 09:15:42 +0000 (GMT) Date: Wed, 6 Dec 2023 10:15:41 +0100 From: Heiko Carstens To: Alexander Gordeev , Claudio Imbrenda , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, nrb@linux.ibm.com, nsg@linux.ibm.com, svens@linux.ibm.com, gor@linux.ibm.com, gerald.schaefer@linux.ibm.com Subject: Re: [PATCH v1 1/1] s390: mm: convert pgste locking functions to C Message-ID: <20231206091541.6897-A-hca@linux.ibm.com> References: <20231205173252.62305-1-imbrenda@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-GUID: _8WngSJqXJ2xVMxhWcdvX0MIuhbApuBu X-Proofpoint-ORIG-GUID: _8WngSJqXJ2xVMxhWcdvX0MIuhbApuBu X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.997,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-12-06_06,2023-12-05_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 bulkscore=0 spamscore=0 adultscore=0 suspectscore=0 clxscore=1015 impostorscore=0 malwarescore=0 priorityscore=1501 mlxscore=0 mlxlogscore=389 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000 definitions=main-2312060074 X-Spam-Status: No, score=-0.8 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on agentk.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (agentk.vger.email [0.0.0.0]); Wed, 06 Dec 2023 01:15:59 -0800 (PST) On Wed, Dec 06, 2023 at 10:01:18AM +0100, Alexander Gordeev wrote: > On Tue, Dec 05, 2023 at 06:32:52PM +0100, Claudio Imbrenda wrote: > ... > > + do { > > + value = __atomic64_or_barrier(PGSTE_PCL_BIT, ptr); > > Would it make sense to cpu_relax() here, e.g with a follow-up patch? No, because cpu_relax() is a no-op on our architecture (besides that it translates to barrier(); but __atomic64_or_barrier() obviously comes also with barrier() semantics). We used to do diag 0x44 with cpu_relax() but that caused many performance problems, therefore we removed diag 0x44 completely from the kernel quite some time ago. See also commit 1b68ac8678a8 ("s390: remove last diag 0x44 caller").