Messages in this thread Patch in this message | | | From | Waiman Long <> | Subject | [PATCH] locking/lockdep: Use local_irq_save() with call_rcu() | Date | Tue, 22 Dec 2020 17:55:53 -0500 |
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The following lockdep splat was hit:
[ 560.638354] WARNING: CPU: 79 PID: 27458 at kernel/rcu/tree_plugin.h:1749 call_rcu+0x6dc/0xf00 : [ 560.647761] RIP: 0010:call_rcu+0x6dc/0xf00 [ 560.647763] Code: 0f 8f 29 04 00 00 e8 93 da 1c 00 48 8b 3c 24 57 9d 0f 1f 44 00 00 e9 19 fa ff ff 65 8b 05 38 83 c4 49 85 c0 0f 84 cd fb ff ff <0f> 0b e9 c6 fb ff ff e8 b8 45 51 00 4c 89 f2 48 b8 00 00 00 00 00 [ 560.647764] RSP: 0018:ff11001050097b58 EFLAGS: 00010002 [ 560.647766] RAX: 0000000000000001 RBX: ffffffffbb1f3360 RCX: 0000000000000001 [ 560.647766] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffb99bac9c [ 560.647767] RBP: 1fe220020a012f73 R08: 000000010004005c R09: dffffc0000000000 [ 560.647768] R10: dffffc0000000000 R11: 0000000000000003 R12: ff1100105b7f70e1 [ 560.647769] R13: ffffffffb635d8a0 R14: ff1100105b7f72d8 R15: ff1100105b7f7040 [ 560.647770] FS: 00007fd9b3437080(0000) GS:ff1100105b600000(0000) knlGS:0000000000000000 [ 560.647771] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 560.647772] CR2: 00007fd9b30112bc CR3: 000000105e898006 CR4: 0000000000761ee0 [ 560.647773] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 560.647773] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 560.647774] PKRU: 55555554 [ 560.647774] Call Trace: [ 560.647778] ? invoke_rcu_core+0x180/0x180 [ 560.647782] ? __is_module_percpu_address+0xed/0x440 [ 560.647787] lockdep_unregister_key+0x2ab/0x5b0 [ 560.647791] destroy_workqueue+0x40b/0x610 [ 560.647862] xlog_dealloc_log+0x216/0x2b0 [xfs] :
This splat is caused by the fact that lockdep_unregister_key() uses raw_local_irq_save() which doesn't update the hardirqs_enabled percpu flag. The call_rcu() function, however, will call lockdep_assert_irqs_disabled() to check the hardirqs_enabled flag which remained set in this case.
Fix this problem by using local_irq_save()/local_irq_restore() pairs whenever call_rcu() is being called.
I think raw_local_irq_save() function can be used if no external function is being called except maybe printk() as it means another lockdep problem exists.
Fixes: a0b0fd53e1e67 ("locking/lockdep: Free lock classes that are no longer in use") Signed-off-by: Waiman Long <longman@redhat.com> --- kernel/locking/lockdep.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index c1418b47f625..2a37af77ede6 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -5884,7 +5884,7 @@ static void free_zapped_rcu(struct rcu_head *ch) if (WARN_ON_ONCE(ch != &delayed_free.rcu_head)) return; - raw_local_irq_save(flags); + local_irq_save(flags); lockdep_lock(); /* closed head */ @@ -5898,7 +5898,7 @@ static void free_zapped_rcu(struct rcu_head *ch) call_rcu_zapped(delayed_free.pf + delayed_free.index); lockdep_unlock(); - raw_local_irq_restore(flags); + local_irq_restore(flags); } /* @@ -5941,13 +5941,13 @@ static void lockdep_free_key_range_reg(void *start, unsigned long size) init_data_structures_once(); - raw_local_irq_save(flags); + local_irq_save(flags); lockdep_lock(); pf = get_pending_free(); __lockdep_free_key_range(pf, start, size); call_rcu_zapped(pf); lockdep_unlock(); - raw_local_irq_restore(flags); + local_irq_restore(flags); /* * Wait for any possible iterators from look_up_lock_class() to pass @@ -6043,7 +6043,7 @@ static void lockdep_reset_lock_reg(struct lockdep_map *lock) unsigned long flags; int locked; - raw_local_irq_save(flags); + local_irq_save(flags); locked = graph_lock(); if (!locked) goto out_irq; @@ -6054,7 +6054,7 @@ static void lockdep_reset_lock_reg(struct lockdep_map *lock) graph_unlock(); out_irq: - raw_local_irq_restore(flags); + local_irq_restore(flags); } /* @@ -6098,7 +6098,11 @@ void lockdep_unregister_key(struct lock_class_key *key) if (WARN_ON_ONCE(static_obj(key))) return; - raw_local_irq_save(flags); + /* + * local_irq_save() should be used as call_rcu() will check + * hardirqs_enabled state. + */ + local_irq_save(flags); if (!graph_lock()) goto out_irq; @@ -6115,7 +6119,7 @@ void lockdep_unregister_key(struct lock_class_key *key) call_rcu_zapped(pf); graph_unlock(); out_irq: - raw_local_irq_restore(flags); + local_irq_restore(flags); /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */ synchronize_rcu(); -- 2.18.1
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