When to use a freezeable workqueue?

[Stefan Richter]

In which situations is create_freezeable_workqueue() to be preferred
over create_singlethread_workqueue()?

Is a freezable worqueue preferable whenever the worker thread /can/ be
frozen, or is it only to be used if the thread /must/ be frozen during
suspend?

Thanks,

[Rafael J. Wysocki]

Post by Stefan Richter
In which situations is create_freezeable_workqueue() to be preferred
over create_singlethread_workqueue()?
Is a freezable worqueue preferable whenever the worker thread /can/ be
frozen, or is it only to be used if the thread /must/ be frozen during
suspend?

The latter, IMO.

Generally, if you want it to be frozen.

Greetings,
Rafael
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[Alan Stern]

Post by Rafael J. Wysocki

Post by Stefan Richter
In which situations is create_freezeable_workqueue() to be preferred
over create_singlethread_workqueue()?
Is a freezable worqueue preferable whenever the worker thread /can/ be
frozen, or is it only to be used if the thread /must/ be frozen during
suspend?

The latter, IMO.
Generally, if you want it to be frozen.

A good example of a reason for making a workqueue freezable is that the
workqueue contains entries which would cause a suspended device to be
resumed. Obviously you don't want such things to happen while the
system is going to sleep. A little less obviously, there might also be
problems if such a routine ran while the system was waking up.

Another reason might be that the workqueue contains entries which would
try to register or unregister a device. Such actions aren't a good
idea at times when the PM core is iterating through a list of all
devices in order to suspend or resume them. And in the future such
actions may block, effectively freezing the workqueue anyway -- which
could be troublesome if you don't want the workqueue to be frozen!

Alan Stern

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