From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793089084; b=4R0dOycmzI3KY+wP61IjivM1NmBRs+k+3KFZxCR/BihGrtnTVsm9K3fOVtNgesFT6rhm ti1lz9ZMz0p6OtcXc4vyKyF7UFxFzTusOfFbSqlVKIvoaAAVxBg7HeV1xIySqcxWCaa6k vHyyxY3QAPGeW28O505joRGi40WjcGZUBmgcRlt1Dnp1PMpAlu40DPLPZBdbUCbqpPmEv WPIzqt0lIOMqj8TvDnEP4I4alNVEDjeY0s2NF0DAY73D40TlxhQhcKEENlVbw7NTAwdSY eIRzNTy1PD93b2YLz6LY4FlD0Gx5PFMQxxQmfwddClwbKYhk/hVOz/GWvgdrVUPtcRA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793089084; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=D64FFgpc7INZHjHGIMuz6fOYnjN+R/6alnjku+MmCwI=; b=5WYcosjOUjDp6i17GqjkRElD8kA/jnx9OgcWLJQxL9jq5yH8qP1Dk8oZEbCIer3mz2Lp kAOgZn4Uefm1iOhO6p6WIjvH4GnYNNBGM1fzpGGUC6NQvR1GrFENPIT14kJIqHV1vcvcH amT5oe3RpDBh8YRJ8frT4yjkCx5CeMicpvCDx9/vay1vbxcryYricw0X6gwuj054Z7VP1 v5XASiYuqGCoRhx0k6J62Ow3+H2V/IflrGtnX3DWNNE/u+e4MakvMr+eiyfuUU6E21NIm 4z5+tpuFIvepnS7Gjt135c3cghfnPnF6/1dR37NERlNfDzGJ5hM/w2k7amxhrHaawLQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=lrkj80Hq; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 49D65606A320; Tue, 27 Oct 2026 08:18:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=lrkj80Hq Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8565F1F01825; Tue, 27 Oct 2026 08:17:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793089083; bh=D64FFgpc7INZHjHGIMuz6fOYnjN+R/6alnjku+MmCwI=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=lrkj80HqsRK7SmEUA0UlfQ9awwfrnZbTGOTFJ38sN0K5sYRFKCiWceFy/zEcA5N7K X/+Ja8dZnecwCLwqQW2Q53xYQZvfTTZvXc/UlZpQ3ww44q5sovpt7pTsmVFSsALwmW con0FeRikx0qegOPeuI08/JqIvHO7h8RUPar2Oksdd8psB92RcYHO67CJO4Oifo4bl 4OdMIpYuvOM127oapLRHduPwvwZb4shBXArXcUwWQ3OGDl6t28H8bKbs77c3ilGNzD RxpfugSOkHtwZ9bqmFJhB2XCngY1YfFKNWjupoESw2HcBJREXTXw0o5pJ9DqJ4U+FM VgHlaWwITa29Q== Date: Tue, 27 Oct 2026 10:17:41 +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, Josef Bacik , stable@vger.kernel.org Subject: Re: [PATCH 24/46] mm/userfaultfd: wake all waiters on unregister Message-ID: References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-24-6f74bec9a5bb@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261027-fixes_core-v1-24-6f74bec9a5bb@kernel.org> On Tue, Oct 27, 2026 at 12:17:44AM +0100, David Hildenbrand (Arm) wrote: > From: Josef Bacik > > UFFDIO_UNREGISTER only wakes pending faults if VM_UFFD_MISSING is set. > Threads waiting on write-protect, minor or RWP faults can therefore remain > asleep after unregistering a range that does not track missing faults. > > Wake pending faults regardless of the registration mode so they can retry > without an explicit UFFDIO_WAKE or closing the userfaultfd. This matches > the existing behavior for missing faults, including removing unread fault > messages for the woken waiters. > > Fix generated by an LLM and sent by Josef Bacik in private. > > Fixes: 63b2d4174c4a ("userfaultfd: wp: add the writeprotect API to userfaultfd ioctl") > Cc: stable@vger.kernel.org > Signed-off-by: Josef Bacik > [ david: rebase; simplify description ] > Signed-off-by: David Hildenbrand (Arm) Reviewed-by: Mike Rapoport (Microsoft) > --- > mm/userfaultfd.c | 22 ++++++++++------------ > 1 file changed, 10 insertions(+), 12 deletions(-) > > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > index 7e30b5ff17be1..2122676c4220f 100644 > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -3977,6 +3977,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, > > ret = 0; > for_each_vma_range(vmi, vma, end) { > + struct userfaultfd_wake_range range; > + > cond_resched(); > > /* VMA not registered with userfaultfd. */ > @@ -3994,18 +3996,14 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, > /* Prevent new userfaults from being queued after the wakeup. */ > vma_start_write(vma); > > - if (userfaultfd_missing(vma)) { > - /* > - * Wake any concurrent pending userfault while > - * we unregister, so they will not hang > - * permanently and it avoids userland to call > - * UFFDIO_WAKE explicitly. > - */ > - struct userfaultfd_wake_range range; > - range.start = start; > - range.len = vma_end - start; > - wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range); > - } > + /* > + * Wake any concurrent pending userfault while we unregister, > + * so they will not hang permanently and it avoids userland to > + * call UFFDIO_WAKE explicitly. > + */ > + range.start = start; > + range.len = vma_end - start; > + wake_userfault(ctx, &range); > > vma = userfaultfd_clear_vma(&vmi, prev, vma, > start, vma_end); > > -- > 2.43.0 > -- Sincerely yours, Mike.