From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BE863606A31B for ; Tue, 27 Oct 2026 08:22:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=ZxhF72fi; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=XcnbEhAI DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Unsubscribe-Post:List-Owner; bh=F88x0w6RcEa+c5taIt0Fmt+oPbV+qXUJjPjIECkCifM=; b=ZxhF72fiXpoP7UEYV/ksOsQnvQ IuzXRuTBA4aO0gzfkP2JwQys8li9kyO0NFpjF6UBBpxaP/SbXLoNwBldGXUtl+JD987BxIuDlqyES j1w4olxy6OYsq8fi5mrEEtzJQChlbVuThFv1x5sNMmNZVTI/NRBWSLnlkFmzM5pGftpWdd4uRzfct lSQAzVNR/8D8F8kX3nTYf3ary8GXWBNpxCGZrwjfMgpvD2jxmqlUe0t0rXY/ojiB0VtPDb4AjqAKJ 291WG7wOcjNPhGGqlRIBKdj9gYiG3dH3v6ml5MSgNUTAxtFprXYlaCsZ1h1dibsl6DISq7jADBUfw +W7rrS2g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLcRm-000000041Sc-3eiV; Tue, 27 Oct 2026 08:22:18 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLcRl-000000041SU-3GAl for kexec@lists.infradead.org; Tue, 27 Oct 2026 08:22:17 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 2FB0860052; Tue, 27 Oct 2026 08:22:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 132EB1F01825; Tue, 27 Oct 2026 08:21:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793089336; bh=F88x0w6RcEa+c5taIt0Fmt+oPbV+qXUJjPjIECkCifM=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=XcnbEhAIT53D3Hun+lr/E6g8U6iRmEJKDft/fCMNmTrAnwk0hAOsyjOokbVPvXEp4 /DPpT5Su9B/w3gWyP9HIp6tCbM8SpfFZQEHmk9xZRAFv8vtovKBHP6oMqM2laor/ar P09hpU7MLdF9KtuqzyyOT3LFejOV+LPLAbIgOliERfOsJ89eZuESqQurxPzGdarj2T 8EyrmmZ5UZbvTI7dzlnWbVesHv53x07RfUr1UgzVZx1w/Da9SXe+VMmXlfYIiXPrGF gCrBiBDheLyK5D4iKWh7VKsJm6UWGTipezUjwklfkuNFfwKK/QHJ4IhVCDB+Sy/wHO TpCkfYmmCp5fQ== Date: Tue, 27 Oct 2026 10:21:54 +0200 From: Mike Rapoport To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 25/46] mm/userfaultfd: wake waiters when registration modes are removed Message-ID: References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-25-6f74bec9a5bb@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261027-fixes_core-v1-25-6f74bec9a5bb@kernel.org> X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" X-Spam-Status: No, score=-16.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Tue, Oct 27, 2026 at 12:17:45AM +0100, David Hildenbrand (Arm) wrote: > UFFDIO_REGISTER can replace MISSING or MINOR tracking without waking > faults that are already queued. For example, switching an anonymous > range from MISSING to WP leaves a missing-fault waiter asleep until > userspace explicitly wakes it. > > When a registration change removes a UFFD mode, wake waiters in the > affected interval after updating the VMA. The VMA is write-locked at > this point, so no new faults can queue under the old modes and woken > threads cannot retry until mmap_write_unlock(). Waiters for retained > modes in the same interval may also wake and refault. > > The hang reproduces for MISSING-to-WP and MINOR-to-MISSING transitions, > with both read and unread fault events. > > Fixes: 63b2d4174c4a ("userfaultfd: wp: add the writeprotect API to userfaultfd ioctl") > Cc: stable@vger.kernel.org > Signed-off-by: David Hildenbrand (Arm) Reviewed-by: Mike Rapoport (Microsoft) > --- > mm/userfaultfd.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) -- Sincerely yours, Mike.