[PATCH] lockdep: Add nr_save_trace_invocations counter

[John Kacur <jkacur@gmail.com>]

NOT FOR INCLUSION

I created this patch as a result of Peter Zilstra's request to get more 
info from lockdep. This patch is not for inclusion, at least in its 
present form, because it adds some redunant info to /proc/lockdep_stats

However, some of the fields are new, and it is worth examining, and / or 
applying if you are looking at the MAX_STACK_TRACE_ENTRIES too big 
problem.

I generated this patch against a recent tip/master but it applies without 
conflicts to the latest rt kernel as well. Comments are welcome, in fact 
they are appreciated.

>From 5181c0296dd1549e4e706ff25a4cd81a1d90137d Mon Sep 17 00:00:00 2001
From: John Kacur <jkacur@redhat.com>
Date: Thu, 22 Apr 2010 17:02:42 +0200
Subject: [PATCH] lockdep: Add nr_save_trace_invocations counter

Add the nr_save_trace_invocations counter which counts the number of
time save_trace() is invoked when relevant for trace enteries.

This means, those invocations from mark_lock() and add_lock_to_list()

When called from mark_lock() we break it down into LOCKSTATE categories.

Signed-off-by: John Kacur <jkacur@redhat.com>
---
 kernel/lockdep.c           |   20 ++++++++++++++++++++
 kernel/lockdep_internals.h |    2 ++
 kernel/lockdep_proc.c      |   23 +++++++++++++++++++++++
 3 files changed, 45 insertions(+), 0 deletions(-)

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 78325f8..f921576 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -371,6 +371,10 @@ static int verbose(struct lock_class *class)
 unsigned long nr_stack_trace_entries;
 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
 
+/* Calls to save_trace() from mark_lock() and add_lock_to_list() only*/
+unsigned long nr_save_trace_invocations;
+unsigned long nr_save_trace_invocations_type[LOCK_USAGE_STATES];
+
 static int save_trace(struct stack_trace *trace)
 {
 	trace->nr_entries = 0;
@@ -410,6 +414,19 @@ static int save_trace(struct stack_trace *trace)
 	return 1;
 }
 
+/*
+ * This function is only called from mark_lock() and add_lock_to_list()
+ * which are only called when holding the graph_lock. This counter
+ * piggybacks off of that lock
+ */
+static void inc_save_trace_invocations(enum lock_usage_bit new_bit)
+{
+	nr_save_trace_invocations++;
+	if (WARN_ON(new_bit >= LOCK_USAGE_STATES))
+		return;
+	nr_save_trace_invocations_type[new_bit]++;
+}
+
 unsigned int nr_hardirq_chains;
 unsigned int nr_softirq_chains;
 unsigned int nr_process_chains;
@@ -449,6 +466,7 @@ static const char *usage_str[] =
 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
 #include "lockdep_states.h"
 #undef LOCKDEP_STATE
+#undef __USAGE
 	[LOCK_USED] = "INITIAL USE",
 };
 
@@ -816,6 +834,7 @@ static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
 	if (!entry)
 		return 0;
 
+	nr_save_trace_invocations++;
 	if (!save_trace(&entry->trace))
 		return 0;
 
@@ -2615,6 +2634,7 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
 
 	hlock_class(this)->usage_mask |= new_mask;
 
+	inc_save_trace_invocations(new_bit);
 	if (!save_trace(hlock_class(this)->usage_traces + new_bit))
 		return 0;
 
diff --git a/kernel/lockdep_internals.h b/kernel/lockdep_internals.h
index 8d7d4b6..6149358 100644
--- a/kernel/lockdep_internals.h
+++ b/kernel/lockdep_internals.h
@@ -84,6 +84,8 @@ extern unsigned long nr_list_entries;
 extern unsigned long nr_lock_chains;
 extern int nr_chain_hlocks;
 extern unsigned long nr_stack_trace_entries;
+extern unsigned long nr_save_trace_invocations;
+extern unsigned long nr_save_trace_invocations_type[LOCK_USAGE_STATES];
 
 extern unsigned int nr_hardirq_chains;
 extern unsigned int nr_softirq_chains;
diff --git a/kernel/lockdep_proc.c b/kernel/lockdep_proc.c
index 59b76c8..ef5f372 100644
--- a/kernel/lockdep_proc.c
+++ b/kernel/lockdep_proc.c
@@ -215,8 +215,24 @@ static void lockdep_stats_debug_show(struct seq_file *m)
 #endif
 }
 
+#define __USAGE(__STATE)	\
+[LOCK_USED_IN_##__STATE] = "LOCK_USED_IN_"__stringify(__STATE),	\
+[LOCK_ENABLED_##__STATE] = "LOCK_ENABLED_"__stringify(__STATE), \
+[LOCK_USED_IN_##__STATE##_READ] = "LOCK_USED_IN_"__stringify(__STATE)"_READ", \
+[LOCK_ENABLED_##__STATE##_READ] = "LOCK_ENABLED_"__stringify(__STATE)"_READ",
+
+static const char *lockstate_tostr[] =
+{
+#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
+#include "lockdep_states.h"
+#undef LOCKDEP_STATE
+#undef __USAGE
+	[LOCK_USED] = "LOCK_USED",
+};
+
 static int lockdep_stats_show(struct seq_file *m, void *v)
 {
+	int bit;
 	struct lock_class *class;
 	unsigned long nr_unused = 0, nr_uncategorized = 0,
 		      nr_irq_safe = 0, nr_irq_unsafe = 0,
@@ -307,6 +323,13 @@ static int lockdep_stats_show(struct seq_file *m, void *v)
 			nr_process_chains);
 	seq_printf(m, " stack-trace entries:           %11lu [max: %lu]\n",
 			nr_stack_trace_entries, MAX_STACK_TRACE_ENTRIES);
+	seq_printf(m, " stack-trace invocations: %lu\n",
+			nr_save_trace_invocations);
+
+	for (bit=0; bit < LOCK_USAGE_STATES; bit++)
+		seq_printf(m, "\t%s: %lu\n", lockstate_tostr[bit],
+			       nr_save_trace_invocations_type[bit]);	
+
 	seq_printf(m, " combined max dependencies:     %11u\n",
 			(nr_hardirq_chains + 1) *
 			(nr_softirq_chains + 1) *
-- 
1.6.6.1