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Wed, 12 Mar 2025 15:28:26 -0700 (PDT) Date: Wed, 12 Mar 2025 18:28:22 -0400 From: Peter Xu To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Kefeng Wang , Mike Rapoport , Al Viro , Axel Rasmussen , Pavel Emelyanov , Jinjiang Tu , Dimitris Siakavaras , Andrea Arcangeli Subject: Re: [PATCH] mm/userfaultfd: Fix release hang over concurrent GUP Message-ID: References: <20250312145131.1143062-1-peterx@redhat.com> <20250312150411.f4a5b406600742a49b46d04e@linux-foundation.org> MIME-Version: 1.0 In-Reply-To: <20250312150411.f4a5b406600742a49b46d04e@linux-foundation.org> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: OsVPTLNNTcodwbVIz9097gaohrkcvDjcsYTq5CO2XJk_1741818507 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Stat-Signature: mjdhmbjzmf1bgew6m76jh96qdk9agmwr X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 8A598A000C X-Rspam-User: X-HE-Tag: 1741818511-292092 X-HE-Meta: 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 N/Eq2Pf4 wdDtaEPf0vQMGx2qkHnU5BO7pwPh4JXUDtI70B1+uZSIcOz68Br7XvdWVZdkC64b2DKu1Jj+6cMyQTpaGPz+s40mbsxd0Bt8+X2gELL6Kx5zM7C1fu65tpBemFYiZ8S06h6PRN43DpoUEHkXrQrIv5iPsFo7s91WGJWPc/E1vjofKrJRuCUaZ4apvYcbPq0v37mjZat0/CBbWHzvILsVFSYriNo3HslnAd2tQUOZ5Sm8jEtk0fVA2jSqx+5IpSwH5Hq2JAAonNKGe1EJ61wjdk7DZPsKIsnCRHLdMv+FqJSiCtuJo8T2Yd3zv/EhOhPlOjz8YLJ9fcyl1h0tsyfuLyyx5noTsyX/vHJ22fjmLlIRPcsc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 12, 2025 at 03:04:11PM -0700, Andrew Morton wrote: > It would be good to have a Fixes: target but this bug seems to be so > old that a bare cc:stable should be OK? Yes I agree that should work for us, sorry I forgot to try attach that from time to time.. AFAIU, such unwanted behavior (either GUP hangs, or if before commit 656710a60e36, the behavior could be a SIGBUS returned to GUP racing with the userfaultfd_release()) should exist since the 1st day, but I didn't verify the original commit. Thanks, -- Peter Xu