From mboxrd@z Thu Jan  1 00:00:00 1970
From: Nivedita Singhvi <niv@us.ibm.com>
Subject: Re: softirq-rx and rt_mutex_lock
Date: Wed, 12 May 2010 20:15:00 -0700
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To: ratheesh k <ratheesh.ksz@gmail.com>
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ratheesh k wrote:
> What i learned that - softirq cannot be put into sleep mode .( Am i right )  ?

Hello, Ratheesh,

I'm adding linux-rt (the real-time linux mailing list, which
is the more appropriate place to put this question first) to
the cc list. Also note that linux-net is mostly a dead list,
as you'll observe if you take a look at the archives, and
netdev@vger.kernel.org is the more appropriate mailing list
for network development questions (i.e., search here first).

> I am facing a problem in my RT linux . I used rt_mutex_lock to protect
> one critical section in softirq-rx code . There is some kernel crash
> happens in the critical section .
> 
> PC- > my function in critical section
> LR -> rt_mutex_unlock .
> 
> Why LR is rt_mutex unlock ?
> If rt_mutex_lock can sleep , softirq-rx may sleep ?

If you are running with the RT patchset (CONFIG_PREEMPT_RT),
yes, irqs are now kernel threads. There is more information
here:

https://rt.wiki.kernel.org/index.php/Main_Page

thanks,
Nivedita