linux-kernel - [PATCH 4.19 095/113] locking/lockdep: Fix lock used or unused stats error

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Message-Id: <20190729190718.271983481@linuxfoundation.org>
Date:   Mon, 29 Jul 2019 21:23:02 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Qian Cai <cai@....pw>,
        Yuyang Du <duyuyang@...il.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will.deacon@....com>, arnd@...db.de,
        frederic@...nel.org, Ingo Molnar <mingo@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 095/113] 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: Qian Cai <cai@....pw>
Signed-off-by: Yuyang Du <duyuyang@...il.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Will Deacon <will.deacon@....com>
Cc: arnd@...db.de
Cc: frederic@...nel.org
Link: https://lkml.kernel.org/r/20190709101522.9117-1-duyuyang@gmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/locking/lockdep_proc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c
index 3dd980dfba2d..6cf288eef670 100644
--- a/kernel/locking/lockdep_proc.c
+++ b/kernel/locking/lockdep_proc.c
@@ -210,6 +210,7 @@ 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)
@@ -241,12 +242,12 @@ 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);
-- 
2.20.1