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Tue, 3 Mar 2026 19:57:25 +0000 (GMT) Message-ID: <286d0488aa72b1741f93f900fd5db5c4334a6f50.camel@linux.ibm.com> Subject: Re: [PATCH v5 1/1] PCI/IOV: Add reentrant locking in sriov_add_vfs/sriov_del_vfs for complete serialization From: Niklas Schnelle To: Lukas Wunner , "Ionut Nechita (Wind River)" Cc: linux-pci@vger.kernel.org, helgaas@kernel.org, sebott@linux.ibm.com, bblock@linux.ibm.com, alifm@linux.ibm.com, julianr@linux.ibm.com, dtatulea@nvidia.com, mani@kernel.org, ionut_n2001@yahoo.com, sunlightlinux@gmail.com, linux-kernel@vger.kernel.org In-Reply-To: References: <20260303080903.28693-1-ionut.nechita@windriver.com> <20260303080903.28693-2-ionut.nechita@windriver.com> Autocrypt: addr=schnelle@linux.ibm.com; prefer-encrypt=mutual; keydata=mQINBGHm3M8BEAC+MIQkfoPIAKdjjk84OSQ8erd2OICj98+GdhMQpIjHXn/RJdCZLa58k /ay5x0xIHkWzx1JJOm4Lki7WEzRbYDexQEJP0xUia0U+4Yg7PJL4Dg/W4Ho28dRBROoJjgJSLSHwc 3/1pjpNlSaX/qg3ZM8+/EiSGc7uEPklLYu3gRGxcWV/944HdUyLcnjrZwCn2+gg9ncVJjsimS0ro/ 2wU2RPE4ju6NMBn5Go26sAj1owdYQQv9t0d71CmZS9Bh+2+cLjC7HvyTHKFxVGOznUL+j1a45VrVS XQ+nhTVjvgvXR84z10bOvLiwxJZ/00pwNi7uCdSYnZFLQ4S/JGMs4lhOiCGJhJ/9FR7JVw/1t1G9a UlqVp23AXwzbcoV2fxyE/CsVpHcyOWGDahGLcH7QeitN6cjltf9ymw2spBzpRnfFn80nVxgSYVG1d w75ksBAuQ/3e+oTQk4GAa2ShoNVsvR9GYn7rnsDN5pVILDhdPO3J2PGIXa5ipQnvwb3EHvPXyzakY tK50fBUPKk3XnkRwRYEbbPEB7YT+ccF/HioCryqDPWUivXF8qf6Jw5T1mhwukUV1i+QyJzJxGPh19 /N2/GK7/yS5wrt0Lwxzevc5g+jX8RyjzywOZGHTVu9KIQiG8Pqx33UxZvykjaqTMjo7kaAdGEkrHZ dVHqoPZwhCsgQARAQABtChOaWtsYXMgU2NobmVsbGUgPHNjaG5lbGxlQGxpbnV4LmlibS5jb20+iQ JXBBMBCABBAhsBBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAAhkBFiEEnbAAstJ1IDCl9y3cr+Q/Fej CYJAFAmmAWs8FCQl6sYAACgkQr+Q/FejCYJAn2g//UKzlXOgizdk0wudLooRbGzDo23ktGSPK5Oj9 9o5z6v4Jz5+qOHo5835683cqkMLM9//udA1ZcKV88LVwyfmoHChPW24cWBmOEy7RJOWCR4WeEINaO pZUGF5YOx7oKTkPs511ky2FR0Heg35754pgTuTMEpYzRXr5pNMPS8mHXcXSARFPDPaCF+uBJ9BafO L7XbpSwKRttePsWAlPHbSbloeDApBfHUhcF/pbuM9GNs+c/8V9NK+SwwqNK214t7jaSq9k+19/hfE jvU45nbiYQM4VqGCelxVFRWol93JnwPFp/JaMgxgV1VYFH9Ijtgh+qNVVBqO8bbTjioFKy1bHdprN 9GyPLDxoaI/lBg+5CwKewzazUjFd0xaqZbTXSgNK4ev/IuNI3qZV8tpvZZWwIgZU1K0Bhplt8Sku+ O9Yl2H54erq9zuzwXjqBJtoW0+MaKbe+1gZ/v2/AVE2VeQMugPUWDg+2bpJaApRkeA4xQ9XfeW6Bp It7xYrwwbVhQtWRC0sRh+QNlU9HI28wPSnLWn7HFBeWupaIrxSp4IEL3eHUn8xv4aA8lpdNsHXD/X vqOSUwy5jlTPTlemvwaC9mNHagNdVXng8C6+hxiDLhZ6xH2P4qNHTKmjW61NsdF6Y/HfWP+lmbi8/ 474UNCltDt/fP01ajqogfWZKFymoH0O0KU5pa2xhcyBTY2huZWxsZSA8bmlrbGFzLnNjaG5lbGxlQ GlibS5jb20+iQJUBBMBCAA+AhsBBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAFiEEnbAAstJ1IDCl9y 3cr+Q/FejCYJAFAmmAWusFCQl6sYAACgkQr+Q/FejCYJAtIw//WmQW/Z+SLdfrlDH5J2bvixzFNnO TOvp8uM8vcNZsxZwPXem4AeCXHayCqipxpa0iXWufEIvdMxkBxWvvM//V+rTUgQnJe6nhDxfLGklx 5Mb2H+K/ndS73ElCuA30MPYq7mHr8i3gEmi2ZFX1W47JecJ8hno/DQxhHRG7bd+GFsiKCbsjLWXNq s/VaAK9uyOTQx7m6/2nR8L+Mvl1BrRXwkj7Qp0qxfQSd4r+IVNBzNFOcrGagBqsyHrN7Is7IICktH 9VFl/G8P+hfviHQLnlxw9ltzpM1Dy6N1+BM3kbqD59gX+L6wqiLJI42eh+SHCiy35FvD3AFlYx4jZ MWE6qIgFnbwcL1kvcA7nnwfr3ZizCYPm8e334xXxslXBoRGsvjXSbAeAyZo2dvJXffNHdcDdUbJSl CfOixNGGKiQvs00X9ekfq9WmmRFvmYHu/m3lg1OXnMjFFIO41O51ZdhbEYJiqZEki7jA8Hd9xuWwQ nFDHhacU3xxivZ4BKQGQc+4XZ3yp/q6+7ux9prepRy/LeRyoaAmE67oxEsAgj+qyA3Tfy5nRTDdRQ E//gpaIt9H1VEx+68dRWHroxBQeozpnFPi25AlX3k4/EtVZjcItPWgE9iru1qT4DH3BBrz7Kd1zUw NnQC77zDJyZD2WUj1E+5bftO0aeE+7HZXj3tM/ea0K05pa2xhcyBTY2huZWxsZSA8bmlrbGFzLnNj aG5lbGxlQGdtYWlsLmNvbT6JAlQEEwEIAD4CGwEFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AWIQSds ACy0nUgMKX3Ldyv5D8V6MJgkAUCaYBa6wUJCXqxgAAKCRCv5D8V6MJgkF/TEACOY2kL4NGFIbWeM5 TUhatxqe8c3RT6jvNjq32CkvaK/cSZzBkS0smddyOzxt2WnsvMgkr9cM7P+CevoMwhT3e0lgQbqBD /vXZJjWKddC+iKXeqWkjMVcgCOsWNZ7PWEzRUT5X1AEFq2zzxQAQ/bCWEYNqIbHN4b6G1Wk+2Y598 +KypZ3FS0bwiItnPQOWzOOqJCGxDxaEUuXFx4ah8HtVdtIev8jPS/5uzQO9iG2vZQUWeMEYZtfMHW sbFWqo2A3lxB+KPzNIYFhul4Lyx1CwvKUAGSHOx7FZuc2xI5DYt/Wdh2QyKFYr7xVzv3uwJjeS1+3 6gvyB7DJaQuY+PziNPv4GPr5wy0cRkJ6Ps15fgC6y6wNwoNdNXKlwiuclIsBzJKa7A0pZMIfpCpIJ bEHP7oy3drBRAhIrBx7Lx1lyqqodDqc+ok5IQ5WcKG/TOrH732mTmJX6fxYTiCVxcU4WLJSNZbrZ/ pjF0AWXs7E+onAkQy6RLg/XU1iiU5QdMvug+fTA6TpPSUMdujWtGWUt3/4nC+69AVc8tXtRQTZ7gP t7uIcQFwPqUuJGS26vl0w/6dIABQAyU9acvE3adCZra+/PBKFZi/yxT1WgV1T2mexKSWwQgLcR57J Yp5oWnQRgi/S6fAoskIWkp9UVcfAQPY0p45NwO5cZR9/g06JZmyrQhTmlrbGFzIFNjaG5lbGxlIDx uaWtzQGtlcm5lbC5vcmc+iQJUBBMBCAA+AhsBBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAFiEEnbAA stJ1IDCl9y3cr+Q/FejCYJAFAmmAWusFCQl6sYAACgkQr+Q/FejCYJAz4A/9F+dMhzu7YonagL4qh WDz5IpRD4vzYKOBZ+qwYp1ugJz1BIUppN9i68HKoS4ARfgP97Sv9GpOy9g7L0lymH2MPF8hRPK0Yn 7DKIkeu/r28YWEoWfoVm5reC+gpxMgmxBz4JScE4f6xfa7+Nw0bbTDl+nxftJD7lf/dTiruNJsXph HQnZ5wPXmxeH6XVJikfpyrGe8iJZALbtHtjlx6Omu7NvRGikenB8trrWS5W0F60ZdbqH1HdmDDcrZ pDq6LtAARHK5tGRm0SK6sZpKe3nULFeeCt7T/edk2FC6KVh4sL1jw1kyceX4DjiMffqYBPrhK5gz5 cDIixLBF9C6Wt1ObvuDBrIQf1/3q6EZrUrUuf6qtaXDMuC6cSlShm47qaPEvVYh67O9JZQ7vzvaea UI74DJUb8Pjnz7mTOmMOzsS1gUhCue4n2YSSM6ythioCGb/3bgMGTpuer3JhvZG5s5uKD9yyj8s8x 35qJkCFfjmjVx9s3vSUS48X+cUpYcMispErKzFu7C0YgKoxvJ4XTfXlDBiMFMPYcN67hsb2jeYHVJ wzE+fIZiDx9JLh1oQW2krwjweisE+3glOaKXZKi0fBtkxyH41iemLtLNYZRJopv6ykdl3hiI+Nh+a 3FZJPTo/OpqchMm8XIeDxC4NFFiPMpyLeYzIxO7eZpiGrAjVTE= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Date: Tue, 03 Mar 2026 20:56:24 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzAzMDE2MCBTYWx0ZWRfXwOnyxaiLdVe4 1rI0P2uhTksSuKS5MfTm8J/QAdun3Mnn0yXX+7OTzMuuc0NeHXxQzfhNcLxFabOqRV8o8xP1aub 3JDzzrWKhSsm++tgwFcLguU+aTHo9oNoRuFImEunHEyM7CimIEwd0T++2h/5hkmvcqNGppnPILS X78PZbU8RnCKrfz5yjLeC8bMNjgNc+ugCNKzBIsKVXg4ji4cY6mY+X682Q9Df2RJHdUIeOvn4bA hwOwLbGKqr/xk4Lm3SdLhv+6hDAzveed1y/wwTToLZex7noa5dc7ehKL3F8/XAumwYYwXXzpaH8 +o34/HpDQU7NdZbuIh6vzxN6ZQSFDca7mAQjX2FIxzVoUgqAa0B6FDnhWbYFLx6qjGjTvlaXAjG 7k4SSdDHhLQ633APGNuh1VowFVNosq6o9hgbZIw/9dA340YjVN3Z/rW4yWEO1PqetpfSCrQuAhi 7GQ8NDErmAQRQe5gb4g== X-Proofpoint-ORIG-GUID: iu9XpQexmZC6spQUT-3PV-0EMQgkwYxW X-Proofpoint-GUID: J9bDQzzYakpHOojbiQBInSErwwg9G-lH X-Authority-Analysis: v=2.4 cv=AobjHe9P c=1 sm=1 tr=0 ts=69a73d2b cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=baYKH5ZQAnJv1YqLvkgA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-03_03,2026-03-03_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 lowpriorityscore=0 bulkscore=0 impostorscore=0 malwarescore=0 spamscore=0 clxscore=1011 suspectscore=0 adultscore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2603030160 On Tue, 2026-03-03 at 20:28 +0100, Lukas Wunner wrote: > On Tue, Mar 03, 2026 at 07:19:31PM +0100, Lukas Wunner wrote: > > Also, I would put this in the existing pci_lock_rescan_remove(), > > i.e. without introducing a new _reentrant variant, because these > > deadlocks exist elsewhere. They're known to happen on unplug in > > pciehp as well. >=20 > Actually, scratch this particular comment. The deadlock in pciehp > is actually an AB-BA deadlock, not recursive acquisition. Hi Lukas, Do you have a link to a report or a lockdep splat for this issue? We're currently working on another series restructuring the use of the rescan/remove lock in s390 PCI code to handle another deadlock. And while most of that is s390 specific code this may give helpful insights. Also definitely underlines how tricky this lock is. Thanks, Niklas