audio: when is a "Resource temporarily unavailable"?

Hi,

Bug #28056 involving FreeBSD and OSS exhibits:
warn:oss:AudioRenderClient_ReleaseBuffer write failed: 35 (Resource temporarily unavailable)

My own notes from times as old as wine-1.1.8 show the same error with ALSA:
err:wave:wodPlayer_WriteMaxFrags Error in writing wavehdr. Reason: Resource temporarily unavailable

The symbolic errno constant is EAGAIN=EWOULDBLOCK.

Does anybody have a suspicion when/why this happens?
- is audio simply not reliable?
- is Wine not correctly driving audio output?
- ...?

FWIW, my test experiments outside Wine recently produced EWOULDBLOCK
once despite non-blocking mode in ALSA, when attempting to write a small
number of frames, less than period_size.

Is this failure really temporary or would it be safer
to close or reset the audio device given such an error value?
What's your experience?

Thank you,
    Jörg Höhle