tree 4d31a410dcb0c4df0118f67e1d4ad45a8ae47670
parent 94634a72b1cbc327dccfefd577436576992c644e
author David Benjamin <davidben@google.com> 1614009993 -0500
committer CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org> 1614126490 +0000

Split the FIPS mode PRNG lock in two.

In FIPS mode, we maintain a lock in order to implement clearing DRBG
state on process shutdown. This lock serves two purposes:

1. It protects the linked list of all DRBG states, which needs to be
   updated the first time a thread touches RAND_bytes, when a thread
   exits, and on process exit.

2. It ensures threads alive during process shutdown do not accidentally
   touch DRBGs after they are cleared, by way of taking a ton of read
   locks in RAND_bytes across some potentially time-consuming points.

This means that when one of the rare events in (1) happens, it must
contend with the flurry of read locks in (2). Split these uses into two
locks. The second lock now only ever sees read locks until process
shutdown, and the first lock is only accessed in rare cases.

Change-Id: Ib856c7a3bb937bbfa5d08534031dbf4ed3315cab
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/45844
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>