diff options
Diffstat (limited to 'kernel/locking/rwsem.c')
| -rw-r--r-- | kernel/locking/rwsem.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 29eea50a3e67..884aa08e0624 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -635,7 +635,10 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem) } preempt_disable(); - rcu_read_lock(); + /* + * Disable preemption is equal to the RCU read-side crital section, + * thus the task_strcut structure won't go away. + */ owner = rwsem_owner_flags(sem, &flags); /* * Don't check the read-owner as the entry may be stale. @@ -643,7 +646,6 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem) if ((flags & RWSEM_NONSPINNABLE) || (owner && !(flags & RWSEM_READER_OWNED) && !owner_on_cpu(owner))) ret = false; - rcu_read_unlock(); preempt_enable(); lockevent_cond_inc(rwsem_opt_fail, !ret); @@ -671,12 +673,13 @@ rwsem_spin_on_owner(struct rw_semaphore *sem) unsigned long flags, new_flags; enum owner_state state; + lockdep_assert_preemption_disabled(); + owner = rwsem_owner_flags(sem, &flags); state = rwsem_owner_state(owner, flags); if (state != OWNER_WRITER) return state; - rcu_read_lock(); for (;;) { /* * When a waiting writer set the handoff flag, it may spin @@ -694,7 +697,9 @@ rwsem_spin_on_owner(struct rw_semaphore *sem) * Ensure we emit the owner->on_cpu, dereference _after_ * checking sem->owner still matches owner, if that fails, * owner might point to free()d memory, if it still matches, - * the rcu_read_lock() ensures the memory stays valid. + * our spinning context already disabled preemption which is + * equal to RCU read-side crital section ensures the memory + * stays valid. */ barrier(); @@ -705,7 +710,6 @@ rwsem_spin_on_owner(struct rw_semaphore *sem) cpu_relax(); } - rcu_read_unlock(); return state; } |