From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B227B363C75 for ; Fri, 24 Apr 2026 10:42:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777027363; cv=none; b=naksRdIctYCzndzf719CKp+4QVUJX1Wo7CD8XjAs1/4zYyNcpCJVf5FCin7NcsqD0TnJsp8CBy5fLq0Vh8VN50OufVHSMAkyAjwIiNVTOHrK18r5benVbGmV/hjIWE+7mpTZC/+ofuPHFEdAJ2sHwOOQv73r5LIhcTAHo3np94E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777027363; c=relaxed/simple; bh=nR0iuS/CKyKNZLyYEdgABt6XJMQmCKdEOGfa5uTpvkA=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=YxHvAgznl8lYwt6Xvh+JjDcdt0fKdROk6/HtdD82TBb+yHuUZo24BqM8079/dOnQSoG543Np5eYF51ygdthOtrmCXEZNkRkcNqZWR7BZwA4wuW2wbuiEn87Mxs/02T3ruBHtMZ+bcz3hUUPdsUNYZOMeE0FW/ZrxAruuVmNX0dU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=IWYBmbai; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="IWYBmbai" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2534CC19425; Fri, 24 Apr 2026 10:42:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1777027363; bh=nR0iuS/CKyKNZLyYEdgABt6XJMQmCKdEOGfa5uTpvkA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=IWYBmbailcCty1MPeh6h9jE9H5U5hJVIncLh+4HoUsE7ZZOyQJ473Kf1OS54kV7V1 XM8cfvQOCkb0WSdaGA0u6f/inBwvuHPD/BbNkfRq5J7j5jBcMtbbZdKljHrbUs17gw aO77a7biIJ9LcJyYYit35g5pidTPBUAHq5bsHWRs= Date: Fri, 24 Apr 2026 03:42:42 -0700 From: Andrew Morton To: Arjan van de Ven Cc: linux-mm@kvack.org, syzbot+9722a25de70a85ff48a1@syzkaller.appspotmail.com, baolin.wang@linux.alibaba.com, hughd@google.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [mm?] BUG: sleeping function called from invalid context in shmem_undo_range Message-Id: <20260424034242.b3e888872e8af6bedb882c1c@linux-foundation.org> In-Reply-To: <20260424023524.322251-1-arjan@linux.intel.com> References: <69eab803.a00a0220.17a17.004b.GAE@google.com> <20260424023524.322251-1-arjan@linux.intel.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 23 Apr 2026 19:34:54 -0700 Arjan van de Ven wrote: > This email is created by automation to help kernel developers > deal with a large volume of AI generated bug reports by decoding > oopses into more actionable information. Thanks ;) > > ... > > Potential Solution > > Find the rcu_read_lock() call that is missing its matching > rcu_read_unlock() in the vfs_unlink() / fsnotify_unlink() / > d_delete_notify() code path. Adding a WARN_ON(rcu_read_lock_held()) > to iput() (alongside the existing might_sleep() check) should produce > a backtrace pointing at the exact acquisition site on the next > reproduction. yup, if we had a reproducer! What's missing from the lockdep report is the one thing we want to know - where did that rcu_read_lock() occur? All we have is > #1: ffffffff8e7e5260 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire.constprop.0+0x7/0x30 include/linux/rcupdate.h:300 which isn't very useful! lockdep records the stack trace for the acquisition site, so why didn't we get to see that?