blob: 8c80a2328d4a951112ae796479dccae76fc316df [file] [log] [blame]
From 1123d21bc161ec1b21d8cd7f95b8a4750909d414 Mon Sep 17 00:00:00 2001
From: Boqun Feng <boqun.feng@gmail.com>
Date: Thu, 12 Mar 2020 23:12:55 +0800
Subject: [PATCH] locking/lockdep: Avoid recursion in
lockdep_count_{for,back}ward_deps()
commit 25016bd7f4caf5fc983bbab7403d08e64cba3004 upstream.
Qian Cai reported a bug when PROVE_RCU_LIST=y, and read on /proc/lockdep
triggered a warning:
[ ] DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)
...
[ ] Call Trace:
[ ] lock_is_held_type+0x5d/0x150
[ ] ? rcu_lockdep_current_cpu_online+0x64/0x80
[ ] rcu_read_lock_any_held+0xac/0x100
[ ] ? rcu_read_lock_held+0xc0/0xc0
[ ] ? __slab_free+0x421/0x540
[ ] ? kasan_kmalloc+0x9/0x10
[ ] ? __kmalloc_node+0x1d7/0x320
[ ] ? kvmalloc_node+0x6f/0x80
[ ] __bfs+0x28a/0x3c0
[ ] ? class_equal+0x30/0x30
[ ] lockdep_count_forward_deps+0x11a/0x1a0
The warning got triggered because lockdep_count_forward_deps() call
__bfs() without current->lockdep_recursion being set, as a result
a lockdep internal function (__bfs()) is checked by lockdep, which is
unexpected, and the inconsistency between the irq-off state and the
state traced by lockdep caused the warning.
Apart from this warning, lockdep internal functions like __bfs() should
always be protected by current->lockdep_recursion to avoid potential
deadlocks and data inconsistency, therefore add the
current->lockdep_recursion on-and-off section to protect __bfs() in both
lockdep_count_forward_deps() and lockdep_count_backward_deps()
Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200312151258.128036-1-boqun.feng@gmail.com
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index dbc936ccf149..c56da2843ccc 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1604,9 +1604,11 @@ unsigned long lockdep_count_forward_deps(struct lock_class *class)
this.class = class;
raw_local_irq_save(flags);
+ current->lockdep_recursion = 1;
arch_spin_lock(&lockdep_lock);
ret = __lockdep_count_forward_deps(&this);
arch_spin_unlock(&lockdep_lock);
+ current->lockdep_recursion = 0;
raw_local_irq_restore(flags);
return ret;
@@ -1631,9 +1633,11 @@ unsigned long lockdep_count_backward_deps(struct lock_class *class)
this.class = class;
raw_local_irq_save(flags);
+ current->lockdep_recursion = 1;
arch_spin_lock(&lockdep_lock);
ret = __lockdep_count_backward_deps(&this);
arch_spin_unlock(&lockdep_lock);
+ current->lockdep_recursion = 0;
raw_local_irq_restore(flags);
return ret;
--
2.7.4