Date: Fri, 18 Apr 2008 13:14:24 -0400 From: John Baldwin <jhb@freebsd.org> To: Aristedes Maniatis <ari@ish.com.au> Cc: bzeeb+freebsd+lor@zabbadoz.net, jeff@freebsd.org, Jurgen Weber <jurgen@ish.com.au>, freebsd-stable@freebsd.org, davidxu@freebsd.org Subject: Re: LOR sleepq/scrlock Message-ID: <200804181314.24974.jhb@freebsd.org> In-Reply-To: <B545E3BC-B592-4847-AAF9-4230892FC049@ish.com.au> References: <77E81AD6-FBCC-4D30-A5CB-A9B918D4793F@ish.com.au> <200804101651.24852.jhb@freebsd.org> <B545E3BC-B592-4847-AAF9-4230892FC049@ish.com.au>
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On Thursday 10 April 2008 06:33:40 pm Aristedes Maniatis wrote: > > >> http://www.ish.com.au/s/LOR/1.jpg > >> http://www.ish.com.au/s/LOR/2.jpg > >> http://www.ish.com.au/s/LOR/3.jpg (this overlaps with [2]) > > > > These are all garbage in kuickshow. :( > > They work fine for me in Firefox. But don't know what sort of jpegs > the Sony camera saves. Anyhow I've also now resaved them as png (about > twice the size). Please let me know if that worked. > > http://www.ish.com.au/s/LOR/1.png , etc kuickshow had issues still, but FF worked ok. The specific LOR at the end is real, but a minor one. Basically, the console driver locks (e.g. "sio", "scrlock") are higher in the order than the various thread locks, so any printf while holding a thread lock will trigger a LOR. The real problem at the bottom of the screen though is a real issue. It's a LOR of two different sleepqueue chain locks. The problem is that when setrunnable() encounters a swapped out thread it tries to wakeup proc0, but if proc0 is asleep (which is typical) then its thread lock is a sleep queue chain lock, so waking up a swapped out thread from wakeup() will usually trigger this LOR. I think the best fix is to not have setrunnable() kick proc0 directly. Perhaps setrunnable() should return an int and return true if proc0 needs to be awakened and false otherwise. Then the the sleepq code (b/c only sleeping threads can be swapped out anyway) can return that value from sleepq_resume_thread() and can call kick_proc0() directly once it has dropped all of its own locks. -- John Baldwin
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