Currently, Shared futures are only available when the std feature is enabled because they use std::sync::Mutex internally. This PR changes this so that Shared futures will fall back to using a spinlock when std is not enabled.
Alternatively, Shared could be changed to be generic over a mutex trait (e.g. lock_api::RawMutex, though it isn't implemented for std::sync::Mutex) to allow arbitrary user implementations.
Currently,
Sharedfutures are only available when thestdfeature is enabled because they usestd::sync::Mutexinternally. This PR changes this so thatSharedfutures will fall back to using a spinlock whenstdis not enabled.Alternatively,
Sharedcould be changed to be generic over a mutex trait (e.g.lock_api::RawMutex, though it isn't implemented forstd::sync::Mutex) to allow arbitrary user implementations.