On 2022-02-24 16:29:37 [+0100], Jason A. Donenfeld wrote: > Taking spinlocks from IRQ context is problematic for PREEMPT_RT. That > is, in part, why we take trylocks instead. But apparently this still > trips up various lock dependency analyzers. That seems like a bug in the > analyzers that should be fixed, rather than having to change things > here. Could you please post a lockdep report so I can take a look? > But maybe there's another reason to change things up: by deferring the > crng pre-init loading to the worker, we can use the cryptographic hash > function rather than xor, which is perhaps a meaningful difference when > considering this data has only been through the relatively weak > fast_mix() function. > > The biggest downside of this approach is that the pre-init loading is > now deferred until later, which means things that need random numbers > after interrupts are enabled, but before workqueues are running -- or > before this particular worker manages to run -- are going to get into > trouble. Hopefully in the real world, this window is rather small, > especially since this code won't run until 64 interrupts had occurred. > > Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Eric Biggers <ebiggers@xxxxxxxxxx> > Cc: Theodore Ts'o <tytso@xxxxxxx> > Reviewed-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> Other than that: Acked-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Sebastian
