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Date:      Sat, 24 Jan 2009 16:30:10 -0800
From:      Alfred Perlstein <alfred@freebsd.org>
To:        Maksim Yevmenkin <maksim.yevmenkin@gmail.com>
Cc:        freebsd-current@freebsd.org, current@freebsd.org, Hans Petter Selasky <hselasky@c2i.net>
Subject:   Re: panic: mutex Giant not owned at /usr/src/sys/kern/tty_ttydisc.c:1127
Message-ID:  <20090125003010.GY87077@elvis.mu.org>
In-Reply-To: <bb4a86c70901240138g6a221fd4rbab3945193e4617@mail.gmail.com>
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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* 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?

-Alfred



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