linux-kernel - HELP! KProbes bug

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Date:	Thu, 28 Aug 2008 10:20:12 -0600
From:	"Marlow Weston" <miwesto@...dia.gov>
To:	ananth@...ibm.com, davem@...emloft.net, mhiramata@...hat.com,
	linux-kernel@...r.kernel.org, anil.s.keshavamurthy@...el.com
Subject: HELP!  KProbes bug

Hello persons in the current kernel maintainers file under KProbes:

I can't find this bug reported anywhere nor somewhere useful for 
reporting it, so I chose that location to find people to write.  If 
there is somewhere else I should be sending this to, please tell me and 
I will redirect it there.

I think I have found a KProbes bug when I turn on the KProbes via a proc 
file call instead of via the init code.  The stack trace is attached and 
seems to indicate a locking issue.  Also attached is module code that 
will make this happen.  Any advice on where to start hunting this down 
would be greatly appreciated.

If the KProbes are going by quickly, ie there is no 
schedule_timeout_interrupt(), then the problem doesn't show up.  This 
problem is exacerbated by the probes actually doing things that take 
time while other probes are attempting to register.  Also, I don't 
believe it has to do with any particular probe as which probe locks up 
varies (and my mad attempts at commenting out various probes did not work).

Note: if you do debug this, do not use any kernel later than the 2.6.25 
kernel as somewhere a bug was introduced causing a hang having to do 
with the timeouts, not necessarily with KProbes.

Thank you,
--Marlow Weston

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