Date: Fri, 13 Jan 2006 09:26:27 +0000 (GMT) From: Robert Watson <rwatson@FreeBSD.org> To: Kris Kennaway <kris@obsecurity.org> Cc: freebsd-stable@freebsd.org Subject: Re: RELENG_6 devfs problem Message-ID: <20060113092535.I38874@fledge.watson.org> In-Reply-To: <20060113071932.GA62526@xor.obsecurity.org> References: <200601051154.32092.doconnor@gsoft.com.au> <20060111210323.G28748@fledge.watson.org> <20060113071932.GA62526@xor.obsecurity.org>
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On Fri, 13 Jan 2006, Kris Kennaway wrote: >> What can I do to try and debug it? >> >> Do you use devfs rule sets? I fixed a bug a week or so ago in devfs_rule.c >> in HEAD, and MFC'd the fix today. The symptoms are much what you describe, >> and occur when an invalid rule is proposed -- the right error is returned, >> but a lock is not released resulting in it being unavailable when processes >> try to access device nodes, resulting in eventual deadlock. It's >> devfs_rule.c:1.21 in HEAD, and devfs_rule.c:1.14.2.3 in RELENG_6. I belive >> the bug does not exist in RELENG_5, as there were significant changes in >> devfs locking for 6.0, and those haven't been merged to RELENG_5. >> >> If this doesn't fix it, the normal debugging steps apply -- compile in DDB, >> BREAK_TO_DEBUGGER, and WITNESS. When the wedge occurs, dump the lock state >> (show alllocks), and we'll see if we can track down the problem. > > I don't use rulesets, and I encountered the same problem when using minicom > to talk to serial ports. I didn't yet have time to debug it, but I can > provide instructions for repeating it. I may or may not have time to dig in, but if you could file the details in a PR (if you haven't already) I can try and take a look. Another similar lock leak wouldn't surprise me. "show alllocks" in DDB once the wedge had happened would be very helpful. Robert N M Watson
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