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List:       opensolaris-networking-discuss
Subject:    [networking-discuss] Another question on mutex
From:       wendy <wendyj58 () hotmail ! com>
Date:       2007-03-30 11:29:04
Message-ID: 31751496.1175279374957.JavaMail.Twebapp () oss-app1
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Hi,

Below is the man page of mutex, can someone explain what does the black words mean? \
many of my colleagues are confused. Does it mean that for driver state, we are free \
to change? then how do we protect it?

Wendy

mutex(9F)

               Acquiring a lock in  user  context  that  is  also
               acquired  in interrupt context means that, as long
               as that lock is held, the driver instance  holding
               the  lock  is subject to all the rules and limita-
               tions of interrupt context.

               In most cases, a mutex can and should be  acquired
               and released within the same function.

               Liberal    use    of    debugging    aids     like
               ASSERT(mutex_owned(&mutex))  can help find callers
               of a function which should be holding a mutex  but
               are  not.  This means you need to test your driver
               compiled with DEBUG.

               [b]Do not use a mutex to set driver  state.  However,
               you  should  use  a  mutex to protect driver state
               data.[/b]
               Use per-instance and automatic data where possible
               to  reduce the amount of shared data. Per-instance
               data can be protected by a  per-instance  lock  to
               improve  scalability  and  reduce  contention with
               multiple hardware instances.

               Avoid global data and global mutexes whenever pos-
               sible.

SunOS 5.9           Last change: 16 Mar 2003                    4
 
 
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