Messages in this thread | | | Date | Fri, 31 Aug 2012 11:19:17 +0800 | Subject | [BUG REPORT] Wrong deaklock warning! | From | "Stanley.Miao" <> |
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Hi, All,
I used two spinlocks in my code, and I enabled the following CONFIGs for debugging.
CONFIG_DEBUG_SPINLOCK=y CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_PROVE_LOCKING=y CONFIG_DEBUG_LOCKDEP=y
void abc_init(struct abc_dev *dev) { spin_lock_init(&dev->locka); spin_lock_init(&dev->lockb); }
void set_last_active_blk(struct abc_dev *dev) { spin_lock(&dev->locka); spin_lock(&dev->lockb); /* do something */ spin_unlock(&dev->lockb); spin_unlock(&dev->locka); }
The code above works fine. No Warning.
Becaused of some reasons, I tried to encapsulate the spin_lock API.
typedef spinlock_t shannon_spinlock_t; void abc_spin_lock_init(shannon_spinlock_t *lock) { spin_lock_init((spinlock_t *)lock); }
void abc_spin_lock(abc_spinlock_t *lock) { spin_lock((spinlock_t *)lock); }
void abc_spin_unlock(abc_spinlock_t *lock) { spin_unlock((spinlock_t *)lock); }
Then my code become:
void abc_init(struct abc_dev *dev) { abc_spin_lock_init(&dev->locka); abc_spin_lock_init(&dev->lockb); }
set_last_active_blk(struct abc_dev *dev) { shannon_spin_lock(&dev->locka); shannon_spin_lock(&dev->lockb); /* do something */ shannon_spin_unlock(&dev->lockb); shannon_spin_unlock(&dev->locka); }
Then I got the following Warning:
[ 538.987581] ============================================= [ 538.988776] [ INFO: possible recursive locking detected ] [ 538.989594] 3.1.4+ #1085 [ 538.989984] --------------------------------------------- [ 538.990801] fio/732 is trying to acquire lock: [ 538.991368] (&((spinlock_t *)lock)->rlock){+.+...}, at: [<ffffffff814b6d29>] abc_spin_lock+0xe/0x10 [ 538.992341] [ 538.992341] but task is already holding lock: [ 538.992341] (&((spinlock_t *)lock)->rlock){+.+...}, at: [<ffffffff814b6d29>] abc_spin_lock+0xe/0x10 [ 538.992341] [ 538.992341] other info that might help us debug this: [ 538.992341] Possible unsafe locking scenario: [ 538.992341] [ 538.992341] CPU0 [ 538.992341] ---- [ 538.992341] lock(&((spinlock_t *)lock)->rlock); [ 538.992341] lock(&((spinlock_t *)lock)->rlock); [ 538.992341] [ 538.992341] *** DEADLOCK *** [ 538.992341] [ 538.992341] May be due to missing lock nesting notation [ 538.992341] [ 538.992341] 2 locks held by fio/732: [ 538.992341] #0: ((struct mutex *)lock){+.+.+.}, at: [<ffffffff814b6c10>] abc_mutex_trylock+0xe/0x10 [ 538.992341] #1: (&((spinlock_t *)lock)->rlock){+.+...}, at: [<ffffffff814b6d29>] abc_spin_lock+0xe/0x10 [ 538.992341] [ 538.992341] stack backtrace: [ 538.992341] Pid: 732, comm: fio Not tainted 3.1.4+ #1085 [ 538.992341] Call Trace: [ 538.992341] [<ffffffff8109b5f9>] __lock_acquire+0xff8/0x1864 [ 538.992341] [<ffffffff8110f085>] ? mempool_alloc_slab+0x15/0x17 [ 538.992341] [<ffffffff814b6d29>] ? abc_spin_lock+0xe/0x10 [ 538.992341] [<ffffffff8109c54f>] lock_acquire+0x101/0x12e [ 538.992341] [<ffffffff814b6d29>] ? abc_spin_lock+0xe/0x10 [ 538.992341] [<ffffffff81856d59>] _raw_spin_lock+0x52/0x87 [ 538.992341] [<ffffffff814b6d29>] ? abc_spin_lock+0xe/0x10 [ 538.992341] [<ffffffff814b6d29>] abc_spin_lock+0xe/0x10 [ 538.992341] [<ffffffff814a95f7>] set_last_active_blk+0x74/0x141 [ 538.992341] [<ffffffff814abdcf>] move_to_next_chunk+0xab/0xef
Obviously this is wrong. There are two different spinlocks and it won't cause deadlock. There is no warning if I don't encapsulate the spinlock API.
Stanley
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