Date: Sat, 11 May 2013 14:08:58 -0700 From: Kirk McKusick <mckusick@mckusick.com> To: Marcel Moolenaar <marcel@xcllnt.net> Cc: attilio@FreeBSD.org, Marcel Moolenaar <marcel@FreeBSD.org>, freebsd-fs@FreeBSD.org Subject: Re: svn commit: r250411 - in head/sys: conf kern sys Message-ID: <201305112108.r4BL8w5S027367@chez.mckusick.com> In-Reply-To: <6CBEB766-087B-41F4-B549-2D60F4FD2701@xcllnt.net>
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As a filesystem developer, I am very dependent on being able to get vnode lock order reversal LORs. While I have long wanted the ability to individually identify the benign ones (such as vnode + dirhash which your fix will not eliminate since dirhash is not a vnode), that facility exists only for mutexes at the moment. This latest flurry of emails on your change may hasten the day when Attilio's extension gets added to make the identity for other types of locks available. In the meantime, I do understand your need to silence the offending benign messages. But I would like to suggest that instead of making it a compile time option, that you change it to be conditional using a sysctl such as debug.witness.novnodes (you would need to add the witness debug subclass as I don't think that it currently exists). You can set the default to be enabled (e.g., suppressed vnode warnings). This way if I get a filesystem deadlock bug reported to me, I can ask the user to reenable vnode witness warnings without having to have them build a whole new kernel. Kirk McKusick
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