Date: Tue, 22 May 2007 11:18:08 +0200 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> To: Lawrence Stewart <lstewart@room52.net> Cc: freebsd-hackers@freebsd.org Subject: Re: Writing a plain text file to disk from kernel space Message-ID: <86r6p9md2n.fsf@dwp.des.no> In-Reply-To: <4652AD8C.7000605@room52.net> (Lawrence Stewart's message of "Tue\, 22 May 2007 18\:45\:00 %2B1000") References: <4649349D.4060101@room52.net> <200705150847.38838.marc.loerner@hob.de> <46499491.2010205@room52.net> <f2j5hf$hap$2@sea.gmane.org> <46515DE0.20209@room52.net> <86sl9qtpd1.fsf@dwp.des.no> <4652AD8C.7000605@room52.net>
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Lawrence Stewart <lstewart@room52.net> writes: > After further investigation, it turns out that the pfil input hook I'm > using, which catches packets as they traverse up the network stack, > has no problems, and will happily write to the file using the > kio_write function. However, in the pfil output hook, a call to > kio_write causes a hard reset, with the following text shown on tty0: > > Sleeping thread (tid 100069, pid 613) owns a non-sleepable lock > panic: sleeping thread This is a panic, not a hard reset. Since you are writing kernel code, I assume you have KDB/DDB in your kernel and know how to use it. > If I comment out the kio_write code and put a printf instead, there > are no such problems, so it seems the kio_write function is doing > something that is upsetting the kernel, but only when called from a > function that is acting as a pfil output hook? Strikes me as odd > behaviour. I don't understand which thread the error is in relation > to, why that thread is sleeping or which lock it is referring to. kio_write probably blocks waiting for the write to complete. You can't do that while holding a non-sleepable lock. > I tried wrapping the call to kio_write in a mutex, in case there was a > race condition caused by multiple threads trying to write to the file > at the one time, but that hasn't made a difference at all. It complains about sleeping with a non-sleepable lock held, and your solution is to add another non-sleepable lock? DES --=20 Dag-Erling Sm=C3=B8rgrav - des@des.no
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