tree 94dd61d7a3ff39c61289d4692c14f6376c5e9bd5
parent b0251b12956ed8e9e41f7bf0bbb02b337e17ad52
author David Benjamin <davidben@google.com> 1684786388 -0400
committer Boringssl LUCI CQ <boringssl-scoped@luci-project-accounts.iam.gserviceaccount.com> 1684803861 +0000

Avoid locks in CRYPTO_free_ex_data

Every time we free a type with ex_data (RSA, EC_KEY, DSA, SSL_CTX, SSL,
SSL_SESSION, X509, X509_STORE), we allocate and take a read lock. The
allocation means, if we believe in malloc failures, it is possible to
leak memory on malloc failure. The read lock causes an unnecessary bit
of contention writing to the cache line.

Instead, since we never remove ex_data entries, just thread them in a
singly-linked list. This way we only need to synchronize when to stop
iterating. Add a counter to synchronize that. (Or we could make each
'next' pointers atomic, but this seemed more straightforward.)

(I suspect this doesn't matter much, but it was shorter and we were
already allocating the funcs structures anyway.)

Bug: 570
Change-Id: Ie7ba5cc44f2b71ebd79c8971e784912d53af7f5c
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/60025
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
Auto-Submit: David Benjamin <davidben@google.com>