commit 074bcd40 upstream.

get_random_bytes() usually hasn't full entropy available by the time DRBG
instances are first getting seeded from it during boot. Thus, the DRBG
implementation registers random_ready_callbacks which would in turn
schedule some work for reseeding the DRBGs once get_random_bytes() has
sufficient entropy available.

For reference, the relevant history around handling DRBG (re)seeding in
the context of a not yet fully seeded get_random_bytes() is:

  commit 16b369a9 ("random: Blocking API for accessing
                        nonblocking_pool")
  commit 4c787990 ("crypto: drbg - add async seeding operation")

  commit 205a525c ("random: Add callback API for random pool
                        readiness")
  commit 57225e67 ("crypto: drbg - Use callback API for random
                        readiness")
  commit c2719503 ("random: Remove kernel blocking API")

However,...