Re: [PATCH v6] random: defer fast pool mixing to worker

[Jason A. Donenfeld]

On 2/14/22, Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote:
> to
> | - Does anything anywhere call get_random_xx() before the worker has a
> |   chance to run?
>
> Once you queue a work item I don't think that the scheduler needs to put
> it on the CPU right away. It may have already have other tasks waiting
> including some with a RT priority.
> Also, the lock is irqsave() so they can be users in an interrupt
> handler. I remember the original reason why I made it irqsave is because
> something did kmalloc() and SLUB somehow asked for random bits.

Right. So there are two sides of the questions: 1) how bad is this
actual race, and are there any drivers that do regularly get bit by
this? 2) There's a largeish window between workqueue_init_early()
setting up the system highprio workqueue, and workqueue_init()
enabling queued workers to actually run. Interrupts also get enabled
in the interim. Does anything get bit by that window?

Jason