diff options
| -rw-r--r-- | src/libstd/sys/unix/mutex.rs | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/src/libstd/sys/unix/mutex.rs b/src/libstd/sys/unix/mutex.rs index 185615d01dd..45c600f75f5 100644 --- a/src/libstd/sys/unix/mutex.rs +++ b/src/libstd/sys/unix/mutex.rs @@ -30,13 +30,15 @@ impl Mutex { // a type of PTHREAD_MUTEX_DEFAULT, which has undefined behavior if you // try to re-lock it from the same thread when you already hold a lock // (https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_mutex_init.html). + // This is the case even if PTHREAD_MUTEX_DEFAULT == PTHREAD_MUTEX_NORMAL + // (https://github.com/rust-lang/rust/issues/33770#issuecomment-220847521) -- in that + // case, `pthread_mutexattr_settype(PTHREAD_MUTEX_DEFAULT)` will of course be the same + // as setting it to `PTHREAD_MUTEX_NORMAL`, but not setting any mode will result in + // a Mutex where re-locking is UB. // // In practice, glibc takes advantage of this undefined behavior to // implement hardware lock elision, which uses hardware transactional - // memory to avoid acquiring the lock. - // This is the case even if PTHREAD_MUTEX_DEFAULT == PTHREAD_MUTEX_NORMAL - // (https://github.com/rust-lang/rust/issues/33770#issuecomment-220847521). - // As a consequence, while a transaction is in + // memory to avoid acquiring the lock. While a transaction is in // progress, the lock appears to be unlocked. This isn't a problem for // other threads since the transactional memory will abort if a conflict // is detected, however no abort is generated when re-locking from the |