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Commit ccaa280d authored by Yuyang Du's avatar Yuyang Du Committed by Greg Kroah-Hartman
Browse files

locking/lockdep: Fix lock used or unused stats error 



[ Upstream commit 68d41d8c94a31dfb8233ab90b9baf41a2ed2da68 ]

The stats variable nr_unused_locks is incremented every time a new lock
class is register and decremented when the lock is first used in
__lock_acquire(). And after all, it is shown and checked in lockdep_stats.

However, under configurations that either CONFIG_TRACE_IRQFLAGS or
CONFIG_PROVE_LOCKING is not defined:

The commit:

  091806515124b20 ("locking/lockdep: Consolidate lock usage bit initialization")

missed marking the LOCK_USED flag at IRQ usage initialization because
as mark_usage() is not called. And the commit:

  886532aee3cd42d ("locking/lockdep: Move mark_lock() inside CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING")

further made mark_lock() not defined such that the LOCK_USED cannot be
marked at all when the lock is first acquired.

As a result, we fix this by not showing and checking the stats under such
configurations for lockdep_stats.

Reported-by: default avatarQian Cai <cai@lca.pw>
Signed-off-by: default avatarYuyang Du <duyuyang@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: arnd@arndb.de
Cc: frederic@kernel.org
Link: https://lkml.kernel.org/r/20190709101522.9117-1-duyuyang@gmail.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 484354b2

kernel/locking/lockdep_proc.c

+3 −2
Original line number Diff line number Diff line
@@ -229,6 +229,7 @@ static int lockdep_stats_show(struct seq_file *m, void *v) 
		      nr_hardirq_read_safe = 0, nr_hardirq_read_unsafe = 0,

		      sum_forward_deps = 0;



#ifdef CONFIG_PROVE_LOCKING

	list_for_each_entry(class, &all_lock_classes, lock_entry) {



		if (class->usage_mask == 0)
@@ -260,12 +261,12 @@ static int lockdep_stats_show(struct seq_file *m, void *v) 
		if (class->usage_mask & LOCKF_ENABLED_HARDIRQ_READ)

			nr_hardirq_read_unsafe++;



#ifdef CONFIG_PROVE_LOCKING

		sum_forward_deps += lockdep_count_forward_deps(class);

#endif

	}

#ifdef CONFIG_DEBUG_LOCKDEP

	DEBUG_LOCKS_WARN_ON(debug_atomic_read(nr_unused_locks) != nr_unused);

#endif



#endif

	seq_printf(m, " lock-classes:                  %11lu [max: %lu]\n",

			nr_lock_classes, MAX_LOCKDEP_KEYS);