linux-kernel - Re: BUG: sleeping function called from invalid context at kernel/mutex.c:271

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Message-ID: <20120418135152.GC2493@linux.vnet.ibm.com>
Date:	Wed, 18 Apr 2012 06:51:52 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	"Alexander E. Patrakov" <patrakov@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: BUG: sleeping function called from invalid context at
 kernel/mutex.c:271

On Wed, Apr 18, 2012 at 08:08:46AM -0400, Steven Rostedt wrote:
> On Wed, 2012-04-18 at 10:51 +0600, Alexander E. Patrakov wrote:
> 
> > > > 
> > > > Hmm, this can also be reported if you have an rcu leak. Which would also
> > > > explain your memory leak. RCU is the kernel's "garbage collector" and if
> > > > it gets stuck, then you will definitely start seeing memory leaks, as
> > > > memory wont be freed.
> > > 
> > > If RCU is stuck, you should see RCU CPU stall warnings, which can
> > > give clues as to what is causing RCU to get stuck.
> > 
> > Yes, there were such warnings, but all of them said that the stall ended
> > before dump start. So nothing reportable here, but I have just found
> > that https://bugzilla.novell.com/show_bug.cgi?id=754186 looks quite
> > similar in the sense that it (and duplicates) also has undumpable stalls
> > of increasing length, and IPv6 is in use both at home and at work.
> > 
> 
> Do you see the RT throttling message too? That's a bug with an RT task
> going haywire. If that is happening, an RT task may be preventing an RCU
> grace period to finish, and causing the RCU stalls.

Hmmm...  Maybe I should revisit running the RCU core processing in
real-time kernel threads...  Though it was quite painful the last time
I tried that.

							Thanx, Paul

> Just because they ended, doesn't mean that the problem went a way. If
> RCU is being blocked, you will start to see memory leaks. As I said, RCU
> works as the kernels garbage collector. If it stops or just slows down
> significantly, memory does not get freed.
> 
> -- Steve
> 
> 
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