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Date: Sun, 25 Jan 2009 00:30:16 -0800
From: Julian Elischer <julian@elischer.org>
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To: Alfred Perlstein <alfred@freebsd.org>
References: <20090123154336.GJ60948@e.0x20.net>	<200901232337.05627.hselasky@c2i.net>	<bb4a86c70901231514x7696e457k3a6dc0e59d4daed7@mail.gmail.com>	<200901240952.21670.hselasky@c2i.net>	<bb4a86c70901240138g6a221fd4rbab3945193e4617@mail.gmail.com>
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Cc: freebsd-current@freebsd.org, Hans Petter Selasky <hselasky@c2i.net>,
	current@freebsd.org, Maksim Yevmenkin <maksim.yevmenkin@gmail.com>
Subject: Re: panic: mutex Giant not owned
	at	/usr/src/sys/kern/tty_ttydisc.c:1127
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Alfred Perlstein wrote:
> * Maksim Yevmenkin <maksim.yevmenkin@gmail.com> [090124 01:38] wrote:
>> from what i can see you are _NOT_ using _SPIN_ mutexes (aka spin
>> locks). you are using regular mutexes. let me quote locking(9) man
>> page
>>
>> "
>> Mutexes
>>      Basically (regular) mutexes will deschedule the thread if the mutex can
>>      not be acquired.  A non-spin mutex can be considered to be equivalent to
>>      getting a write lock on an rw_lock (see below),
>> "
>>
>> so, if thread can not get mutex it will be descheduled. this
>> absolutely can not happen in netgraph!
> 
>>From a purely academic standpoint... why can't netgraph use
> standard mutexes?
> 
> Is there a pointer you can give me?

see my later post..
it can, but you really want to be sure that you know who you are 
contending with..

> 
> -Alfred
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