From owner-freebsd-bugs@freebsd.org Thu Dec 28 14:12:18 2017 Return-Path: Delivered-To: freebsd-bugs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 2E088EA0921 for ; Thu, 28 Dec 2017 14:12:18 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 1C6CB7CD31 for ; Thu, 28 Dec 2017 14:12:18 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from bugs.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id vBSECHsm013798 for ; Thu, 28 Dec 2017 14:12:17 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 224479] kernel panic in reboot+swapoff sys call Date: Thu, 28 Dec 2017 14:12:18 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: CURRENT X-Bugzilla-Keywords: patch X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: markmi@dsl-only.net X-Bugzilla-Status: Open X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: freebsd-bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 28 Dec 2017 14:12:18 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D224479 --- Comment #16 from Mark Millard --- (In reply to Konstantin Belousov from comment #14) You have written in the past that for file based (vnode-based) swap files the system is deadlock prone in a manor not under significant user control. >From what I've seen lots of folks set up the file based swap spaces without having a clue that such is the status. I was one of them at one time, following http://www.wonkity.com/~wblock/docs/html/ssd.html#_filesystems_and_trim material for SSDs that gave no hint of the issues involved. If the instructions had told me that I needed to enable the mode of use because of deadlock issues that do not happen with partition based swap spaces, I never would have tied it. I had swap space based deadlocks vastly faster than any sdcard wear out would have occurred: the configuration was simply unreliable over fairly short time frames. Also, the deadlocks are not examples of wear-and-tear. (You might want a better analogy for your point in that respect.) I view FreeBSD as designed to automatically avoid deadlocks for swapping only for partition-based swap spaces. Lesser points but more tied to this report: I was expecting that "shutdown -r now" might stop some processes before initiating the v-node removal, making such processes no longer sources of swap-in activity for later stages. (I was not thinking of any general fix to the deadlocking issues.) reboot, by contrast, I was expecting leaves more processes around that might try to swap-in in an untimely manor. I freely admit my expectations might be garbage-in/garbage-out. I was not expecting the sending of SIGSEGV or other signals to a process that is trying to swap-in after there is effectively nothing available to swap-in from. Does some involved kernel stack need to be in a swapped out state to have the problem that has been described? Or can it be a problem when no kernel stacks are swapped out? --=20 You are receiving this mail because: You are the assignee for the bug.=