Problem:
=======
- Multiple user threads waits for all encryption threads to start
before returing the control to user. But in fil_crypt_thread(),
InnoDB signals that thread is started after incrementing
srv_n_fil_crypt_threads_started variable. For multiple waiters,
pthread_cond_broadcast() would be more appropriate as
it wakes all waiting threads.
Solution:
========
fil_crypt_thread(): Use pthread_cond_broadcast instead of
pthread_cond_signal(fil_crypt_cond) to wake multiple waiter
threads
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