USB-related problem

[Konstantin Belousov]

On Tue, Nov 10, 2015 at 02:25:09AM +0700, Eugene Grosbein wrote:
> On 09.11.2015 22:53, Adrian Chadd wrote:
> > ok, let's get it to hang, then break into ddb and do 'show
> > allthreads', 'show alllocks', 'bufvars' with my vfs_bio.c patch, etc.
> 
> I've re-read https://www.freebsd.org/doc/en/books/developers-handbook/kerneldebug-deadlocks.html
> and rebuilt kernel with additional debugging and reproduced the problem again to supply
> more vfs lock info:

You have syncer running with the buffer arena mutex locked.  This probably
means that you have DIAGNOSTIC option turned on, do you ?  If yes,
set debug.vmem_check to zero, otherwise it just eats your anemic CPU.

Also, I am curious what is the value of vfs.unmapped_buf_allowed on
your platform.