Merge "audioflinger: update comment on mutex locking order"

// state changes or resource modifications. Always respect the following order

// if multiple mutexes must be acquired to avoid cross deadlock:

// AudioFlinger -> ThreadBase -> EffectChain -> EffectModule

// AudioHandle -> ThreadBase -> EffectChain -> EffectModule

// In addition, methods that lock the AudioPolicyService mutex (getOutputForEffect(),

// startOutput()...) should never be called with AudioFlinger or Threadbase mutex locked

// to avoid cross deadlock with other clients calling AudioPolicyService methods that in turn

// call AudioFlinger thus locking the same mutexes in the reverse order.

// startOutput(), getInputForAttr(), releaseInput()...) should never be called with AudioFlinger or

// Threadbase mutex locked to avoid cross deadlock with other clients calling AudioPolicyService

// methods that in turn call AudioFlinger thus locking the same mutexes in the reverse order.

// The EffectModule class is a wrapper object controlling the effect engine implementation

// in the effect library. It prevents concurrent calls to process() and command() functions