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| author | Boqun Feng <boqun.feng@gmail.com> | 2020-03-12 23:12:55 +0800 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2020-03-20 13:06:25 +0100 |
| commit | 25016bd7f4caf5fc983bbab7403d08e64cba3004 (patch) | |
| tree | d79ed47688ae18f1e52a6e102d79ec55775ac92f /kernel/locking | |
| parent | 5d0c9b0eb8ab2dd540919174abe75aa3b86b802f (diff) | |
| download | linux-25016bd7f4caf5fc983bbab7403d08e64cba3004.tar.gz | |
locking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps()
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
Diffstat (limited to 'kernel/locking')
| -rw-r--r-- | kernel/locking/lockdep.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index e55c4ee14e64..2564950a402c 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1723,9 +1723,11 @@ 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; @@ -1750,9 +1752,11 @@ 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; |