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SubjectRe: [ 01/23] [Suspend2] Make workqueues freezeable.
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Hi Rafael.

On Friday 27 January 2006 09:17, Rafael J. Wysocki wrote:
> Hi,
>
> On Thursday, 26 January 2006 04:45, Nigel Cunningham wrote:
> > Prior to this patch, kernel threads and workqueues are unconditionally
> > unfreezeable. This patch reverses that behaviour, making the default
> > for kernel processes to be frozen. New variations of the routines for
> > starting kernel threads and workqueues (containing _nofreeze_) allow
> > threads that need to run during suspend to be made nofreeze again.
>
> This looks like "let's make everything freezable and hunt for things that
> must not be frozen" kind of approach, but isn't it error-prone? I mean,
> for example, if someone creates a kernel thread that in fact must not
> be frozen, but forgets to use the _nofreeze_ call, things will break for
> some people and the problem will be worse than the current one,
> it seems.

You're right that the default is now to freeze threads. This is mostly because
the majority of kernel threads can and should be frozen because they're not
needed. If a thread is frozen which shouldn't be, the user (which will
hopefully be the developer testing their work) will experience a deadlock
when they try to suspend. If, on the other hand, we let threads run that
should be frozen, well - the outcome depends on what is done when the thread
should be frozen. Obviously it doesn't hurt too much to let kernel threads
run, or we'd see problems at the moment. For this reason, I consider this
patch more to be a nicety than a necessity. Nice because it makes kernel
threads behave in a manner consistent with what happens to userspace (hence
defaulting to freezing, rather than not).

Regards,

Nigel
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