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220 lines
4.5 KiB
220 lines
4.5 KiB
// SPDX-License-Identifier: GPL-2.0 |
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#include <linux/export.h> |
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#include <linux/lockref.h> |
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#if USE_CMPXCHG_LOCKREF |
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/* |
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* Note that the "cmpxchg()" reloads the "old" value for the |
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* failure case. |
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*/ |
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#define CMPXCHG_LOOP(CODE, SUCCESS) do { \ |
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int retry = 100; \ |
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struct lockref old; \ |
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BUILD_BUG_ON(sizeof(old) != 8); \ |
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old.lock_count = READ_ONCE(lockref->lock_count); \ |
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while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) { \ |
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struct lockref new = old, prev = old; \ |
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CODE \ |
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old.lock_count = cmpxchg64_relaxed(&lockref->lock_count, \ |
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old.lock_count, \ |
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new.lock_count); \ |
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if (likely(old.lock_count == prev.lock_count)) { \ |
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SUCCESS; \ |
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} \ |
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if (!--retry) \ |
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break; \ |
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cpu_relax(); \ |
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} \ |
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} while (0) |
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#else |
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#define CMPXCHG_LOOP(CODE, SUCCESS) do { } while (0) |
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#endif |
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/** |
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* lockref_get - Increments reference count unconditionally |
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* @lockref: pointer to lockref structure |
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* |
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* This operation is only valid if you already hold a reference |
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* to the object, so you know the count cannot be zero. |
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*/ |
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void lockref_get(struct lockref *lockref) |
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{ |
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CMPXCHG_LOOP( |
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new.count++; |
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, |
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return; |
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); |
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spin_lock(&lockref->lock); |
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lockref->count++; |
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spin_unlock(&lockref->lock); |
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} |
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EXPORT_SYMBOL(lockref_get); |
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/** |
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* lockref_get_not_zero - Increments count unless the count is 0 or dead |
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* @lockref: pointer to lockref structure |
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* Return: 1 if count updated successfully or 0 if count was zero |
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*/ |
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int lockref_get_not_zero(struct lockref *lockref) |
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{ |
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int retval; |
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CMPXCHG_LOOP( |
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new.count++; |
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if (old.count <= 0) |
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return 0; |
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, |
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return 1; |
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); |
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spin_lock(&lockref->lock); |
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retval = 0; |
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if (lockref->count > 0) { |
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lockref->count++; |
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retval = 1; |
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} |
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spin_unlock(&lockref->lock); |
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return retval; |
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} |
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EXPORT_SYMBOL(lockref_get_not_zero); |
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/** |
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* lockref_put_not_zero - Decrements count unless count <= 1 before decrement |
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* @lockref: pointer to lockref structure |
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* Return: 1 if count updated successfully or 0 if count would become zero |
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*/ |
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int lockref_put_not_zero(struct lockref *lockref) |
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{ |
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int retval; |
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CMPXCHG_LOOP( |
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new.count--; |
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if (old.count <= 1) |
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return 0; |
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, |
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return 1; |
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); |
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spin_lock(&lockref->lock); |
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retval = 0; |
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if (lockref->count > 1) { |
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lockref->count--; |
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retval = 1; |
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} |
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spin_unlock(&lockref->lock); |
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return retval; |
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} |
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EXPORT_SYMBOL(lockref_put_not_zero); |
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/** |
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* lockref_get_or_lock - Increments count unless the count is 0 or dead |
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* @lockref: pointer to lockref structure |
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* Return: 1 if count updated successfully or 0 if count was zero |
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* and we got the lock instead. |
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*/ |
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int lockref_get_or_lock(struct lockref *lockref) |
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{ |
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CMPXCHG_LOOP( |
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new.count++; |
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if (old.count <= 0) |
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break; |
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, |
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return 1; |
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); |
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spin_lock(&lockref->lock); |
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if (lockref->count <= 0) |
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return 0; |
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lockref->count++; |
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spin_unlock(&lockref->lock); |
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return 1; |
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} |
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EXPORT_SYMBOL(lockref_get_or_lock); |
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/** |
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* lockref_put_return - Decrement reference count if possible |
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* @lockref: pointer to lockref structure |
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* |
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* Decrement the reference count and return the new value. |
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* If the lockref was dead or locked, return an error. |
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*/ |
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int lockref_put_return(struct lockref *lockref) |
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{ |
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CMPXCHG_LOOP( |
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new.count--; |
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if (old.count <= 0) |
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return -1; |
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, |
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return new.count; |
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); |
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return -1; |
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} |
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EXPORT_SYMBOL(lockref_put_return); |
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/** |
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* lockref_put_or_lock - decrements count unless count <= 1 before decrement |
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* @lockref: pointer to lockref structure |
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* Return: 1 if count updated successfully or 0 if count <= 1 and lock taken |
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*/ |
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int lockref_put_or_lock(struct lockref *lockref) |
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{ |
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CMPXCHG_LOOP( |
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new.count--; |
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if (old.count <= 1) |
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break; |
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, |
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return 1; |
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); |
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spin_lock(&lockref->lock); |
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if (lockref->count <= 1) |
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return 0; |
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lockref->count--; |
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spin_unlock(&lockref->lock); |
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return 1; |
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} |
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EXPORT_SYMBOL(lockref_put_or_lock); |
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/** |
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* lockref_mark_dead - mark lockref dead |
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* @lockref: pointer to lockref structure |
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*/ |
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void lockref_mark_dead(struct lockref *lockref) |
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{ |
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assert_spin_locked(&lockref->lock); |
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lockref->count = -128; |
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} |
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EXPORT_SYMBOL(lockref_mark_dead); |
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/** |
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* lockref_get_not_dead - Increments count unless the ref is dead |
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* @lockref: pointer to lockref structure |
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* Return: 1 if count updated successfully or 0 if lockref was dead |
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*/ |
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int lockref_get_not_dead(struct lockref *lockref) |
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{ |
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int retval; |
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CMPXCHG_LOOP( |
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new.count++; |
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if (old.count < 0) |
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return 0; |
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, |
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return 1; |
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); |
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spin_lock(&lockref->lock); |
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retval = 0; |
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if (lockref->count >= 0) { |
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lockref->count++; |
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retval = 1; |
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} |
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spin_unlock(&lockref->lock); |
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return retval; |
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} |
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EXPORT_SYMBOL(lockref_get_not_dead);
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