random: remove batched entropy locking
Rather than use spinlocks to protect batched entropy, we can instead disable interrupts locally, since we're dealing with per-cpu data, and manage resets with a basic generation counter. At the same time, we can't quite do this on PREEMPT_RT, where we still want spinlocks-as- mutexes semantics. So we use a local_lock_t, which provides the right behavior for each. Because this is a per-cpu lock, that generation counter is still doing the necessary CPU-to-CPU communication. This should improve performance a bit. It will also fix the linked splat that Jonathan received with a PROVE_RAW_LOCK_NESTING=y. Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Reviewed-by: Eric Biggers <ebiggers@google.com> Suggested-by: Andy Lutomirski <luto@kernel.org> Reported-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net> Tested-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net> Link: https://lore.kernel.org/lkml/YfMa0QgsjCVdRAvJ@latitude/Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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