Commit 8c779229 authored by Bart Van Assche's avatar Bart Van Assche Committed by Ingo Molnar
Browse files

locking/lockdep: Report more stack trace statistics 



Report the number of stack traces and the number of stack trace hash
chains. These two numbers are useful because these allow to estimate
the number of stack trace hash collisions.

Signed-off-by: default avatarBart Van Assche <bvanassche@acm.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/r/20190722182443.216015-5-bvanassche@acm.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 12593b74

kernel/locking/lockdep.c

+29 −0
Original line number Diff line number Diff line
@@ -516,6 +516,35 @@ static struct lock_trace *save_trace(void) 


	return trace;

}



/* Return the number of stack traces in the stack_trace[] array. */

u64 lockdep_stack_trace_count(void)

{

	struct lock_trace *trace;

	u64 c = 0;

	int i;



	for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {

		hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {

			c++;

		}

	}



	return c;

}



/* Return the number of stack hash chains that have at least one stack trace. */

u64 lockdep_stack_hash_count(void)

{

	u64 c = 0;

	int i;



	for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)

		if (!hlist_empty(&stack_trace_hash[i]))

			c++;



	return c;

}

#endif



unsigned int nr_hardirq_chains;

kernel/locking/lockdep_internals.h

+4 −0
Original line number Diff line number Diff line
@@ -140,6 +140,10 @@ extern unsigned int max_bfs_queue_depth; 
#ifdef CONFIG_PROVE_LOCKING

extern unsigned long lockdep_count_forward_deps(struct lock_class *);

extern unsigned long lockdep_count_backward_deps(struct lock_class *);

#ifdef CONFIG_TRACE_IRQFLAGS

u64 lockdep_stack_trace_count(void);

u64 lockdep_stack_hash_count(void);

#endif

#else

static inline unsigned long

lockdep_count_forward_deps(struct lock_class *class)

kernel/locking/lockdep_proc.c

+6 −0
Original line number Diff line number Diff line
@@ -285,6 +285,12 @@ 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);

#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)

	seq_printf(m, " number of stack traces:        %llu\n",

		   lockdep_stack_trace_count());

	seq_printf(m, " number of stack hash chains:   %llu\n",

		   lockdep_stack_hash_count());

#endif

	seq_printf(m, " combined max dependencies:     %11u\n",

			(nr_hardirq_chains + 1) *

			(nr_softirq_chains + 1) *

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