Date: Thu, 05 Oct 2000 14:31:07 -0700 (PDT) From: John Baldwin <jhb@FreeBSD.org> To: Boris Popov <bp@butya.kz> Cc: freebsd-smp@FreeBSD.org, freebsd-current@FreeBSD.org Subject: RE: Problems with kthread_exit() and SMPng Message-ID: <XFMail.001005143107.jhb@FreeBSD.org> In-Reply-To: <Pine.BSF.4.10.10010051724260.43806-200000@lion.butya.kz>
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On 05-Oct-00 Boris Popov wrote:
> Hello,
>
> Currently I'm trying to make KLD which uses kernel threads
> unloadable under recent -current. The prototype of functions looks like
> this:
>
> void
> my_thread(void*arg)
> {
> while(wearewanted) {
> do_something();
> tsleep();
> }
> exited = 1;
> kthread_exit(0);
> }
You need to have Giant before you call kthread_exit().
> my_unload() function called from the module unload event which
> issued from the kldunload() syscall.
>
> Unfortunately, kernel panics in the mtx_exit_hard() function.
> After some examination I've found that two fields in the Giant mutex
> structure set to unexpected values:
Ah, I need to add a KASSERT() to the start of mtx_exit_hard() to verify
that we own the mutex we are releasing.
> ----
> empty mtx_blocked for mutex Giant
> mtx_contested not in any list for mutex Giant
> ----
>
> These messages printed by added diagnostics code. With this patch
> (see attachment) it is possible to load and unload KLD without any
> problems on UP machine except that the above messages printed. However,
> I'm don't know if they are correct. (btw, 4.1 doesn't have this problem).
It is a bogus patch though. If you release a contested mutex, it should always
have someone who is waiting to grab it.
> Any ideas why this happened and how to fix it ?
> --
> Boris Popov
> http://www.butya.kz/~bp/
--
John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
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