Messages in this thread Patches in this message | | | Subject | Re: /proc/lock_stat "stuck" | From | Peter Zijlstra <> | Date | Wed, 21 May 2008 13:29:02 +0200 |
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On Wed, 2008-05-21 at 07:09 -0400, Alan D. Brunelle wrote: > Peter Zijlstra wrote: > > On Tue, 2008-05-20 at 14:09 -0400, Alan D. Brunelle wrote: > >> I'm attempting to use /proc/lock_stat to gather some information during > >> some benchmarking runs, but what I find happens is as follows: > >> > >> 1. I boot the system - 2.6.26-rc3 kernel + CONFIG_LOCK_STAT=y > >> > >> 2. I can then look at /proc/lock_stat, and it has valid-looking values > >> > >> 3. I wait a while, do some stuff, but when I look at /proc/lock_stat > >> again the values have not changed. > >> > >> 4. If I clear the counters - echo 0 > /proc/lock_stat - the counters > >> never increase, and no information besides the headers are output when I > >> cat /proc/lock_stat. > >> > >> > >> Is there something that one needs to do to get counter updates? > > > > Did you get lockdep warnings? Those disable all lock debugging, > > including lockstat. > > Hi Peter - > > Yesterday, during boots I /was/ getting a problem with NVIDIA ck804xrom > registration problems - "Unable to register resource" - it did produce > a stack trace w/ lock calls in the stack. Since then I've cut /way/ back > on my .config, and I don't see that problem anymore, and the lock stats > seem to be updating correctly with this new .config. [If I have time > later today, I'll go back to the old .config and try to track down the > ck804xrom issue.] > > Thanks for the hint about watching for lockdep issues, > Alan
You might like to 'test' these two patches :-)
Subject: lockstat: warn about disabled lock debugging From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Avoid confusion and clearly state lock debugging got disabled.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- kernel/lockdep_proc.c | 4 ++++ 1 file changed, 4 insertions(+)
Index: linux-2.6/kernel/lockdep_proc.c =================================================================== --- linux-2.6.orig/kernel/lockdep_proc.c +++ linux-2.6/kernel/lockdep_proc.c @@ -516,6 +516,10 @@ static void seq_stats(struct seq_file *m static void seq_header(struct seq_file *m) { seq_printf(m, "lock_stat version 0.2\n"); + + if (unlikely(!debug_locks)) + seq_printf(m, "*WARNING* lock debugging disabled!! - possibly due to a lockdep warning\n"); + seq_line(m, '-', 0, 40 + 1 + 10 * (14 + 1)); seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s " "%14s %14s\n",
Subject: lockstat: fix contention points From: Peter Zijlstra <a.p.zijlstra@chello.nl>
blatantly stupid bug..
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- kernel/lockdep.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux-2.6/kernel/lockdep.c =================================================================== --- linux-2.6.orig/kernel/lockdep.c +++ linux-2.6/kernel/lockdep.c @@ -2791,7 +2791,7 @@ found_it: stats = get_lock_stats(hlock->class); if (point < ARRAY_SIZE(stats->contention_point)) - stats->contention_point[i]++; + stats->contention_point[point]++; if (lock->cpu != smp_processor_id()) stats->bounces[bounce_contended + !!hlock->read]++; put_lock_stats(stats);
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