[4.14] Fix for Pisound's MIDI Input getting blocked for a while in rare cases.

[gtrainavicius]

There was a possible race condition which could lead to Input's FIFO queue
to be underflown, causing high amount of processing in the worker thread for
some period of time.

Signed-off-by: Giedrius Trainavicius <giedrius@blokas.io>

Link to 4.9 pull request: #2440

[gtrainavicius]

Thank you for quick turnaround! :)

By the way, what is the policy for 4.9 and 4.14 branches? Should I continue pushing fixes to both branches at the moment? For how long will 4.9 continue to be supported?

[pelwell]

We could have launched the 3B+ with 4.14 but the decision was taken to avoid creating two sets of new bugs - 4.14 going mainstream and 3B+-specific problems. With the launch out of the way and, so far, only a relatively niche networking bug (#2437), we'll probably make the jump to 4.14 within the next week or two.

[pelwell]

4.9 is an LTS kernel, so we'll probably keep it around as the stable branch for a while - we're certainly not blocking submissions for it yet.

[gtrainavicius]

Thank you for the information! 👍