Unlock race condition

[nikolai-b]

If client A tries to unlock:

redis-semaphore/lib/redis/semaphore.rb

Line 89 in 8653045

return false unless locked?

and the hexists returns true.

Then afterwards a different client (B) cleans up expired keys

redis-semaphore/lib/redis/semaphore.rb

Line 142 in 8653045

signal(token)

moving them from the hset into the list.

Now when client A gets to

redis-semaphore/lib/redis/semaphore.rb

Line 90 in 8653045

signal(@tokens.pop)[1]

it will put the token into the list again so it will appear twice.