linux-kernel - Lockdep usage

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Message-ID: <4BCFEBFF.4090505@us.ibm.com>
Date:	Wed, 21 Apr 2010 23:26:07 -0700
From:	Darren Hart <dvhltc@...ibm.com>
To:	"lkml, " <linux-kernel@...r.kernel.org>
CC:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>
Subject: Lockdep usage

I'm having some trouble with lockstat. I've enabled CONFIG_LOCK_STATS 
and then run the following commands to collect the lock statistics for 
the futex_lock test case. I expect this test case to generate a fair 
amount of contention on the futex hash bucket locks, but they don't show 
up in the stats (in fact, nothing shows up in the stats). I have seen 
much longer lock_stat files when I forgot to clear them before the test, 
but no hb locks showed up there either.

Is my usage below incorrect? Do I have to somehow annotate the hb->lock 
in order for lockstat to track it?

This is as of:
commit a3d3203e4bb40f253b1541e310dc0f9305be7c84
Merge: f937331... ec28dcc...
Author: Linus Torvalds <torvalds@...ux-foundation.org>
Date:   Sun Mar 14 20:29:21 2010 -0700


# echo 0 > /proc/lock_stat; echo 1 > /proc/sys/kernel/lock_stat; 
./futex_lock -i10000000 -p1000 -d20; cat /proc/lock_stat > 
lock.lockstat; echo 0 > /proc/sys/kernel/lock_stat
futex_lock: Measure FUTEX_LOCK operations per second
         Arguments: iterations=10000000 threads=256 adaptive=no
                    period=1000 duty-cycle=20%
Result: 731 Kiter/s

# cat lock.lockstat
lock_stat version 0.3
*WARNING* lock debugging disabled!! - possibly due to a lockdep warning
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                               class name    con-bounces    contentions 
   waittime-min   waittime-max waittime-total    acq-bounces 
acquisitions   holdtime-min   holdtime-max holdtime-total
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

#

Thanks,

-- 
Darren Hart
IBM Linux Technology Center
Real-Time Linux Team
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