The `_PySeqLock_EndRead` function needs an acquire fence to ensure that
the load of the sequence happens after any loads within the read side
critical section. The missing fence can trigger bugs on macOS arm64.
Additionally, we need a release fence in `_PySeqLock_LockWrite` to
ensure that the sequence update is visible before any modifications to
the cache entry.
Add _PyType_LookupRef and use incref before setting attribute on type
Makes setting an attribute on a class and signaling type modified atomic
Avoid adding re-entrancy exposing the type cache in an inconsistent state by decrefing after type is updated
Makes sys.settrace, sys.setprofile, and monitoring generally thread-safe.
Mostly uses a stop-the-world approach and synchronization around the code object's _co_instrumentation_version. There may be a little bit of extra synchronization around the monitoring data that's required to be TSAN clean.
This adds a safe memory reclamation scheme based on FreeBSD's "GUS" and
quiescent state based reclamation (QSBR). The API provides a mechanism
for callers to detect when it is safe to free memory that may be
concurrently accessed by readers.
The ID of the owning thread (`rlock_owner`) may be accessed by
multiple threads without holding the underlying lock; relaxed
atomics are used in place of the previous loads/stores.
The number of times that the lock has been acquired (`rlock_count`)
is only ever accessed by the thread that holds the lock; we do not
need to use atomics to access it.
Makes _PyType_Lookup thread safe, including:
Thread safety of the underlying cache.
Make mutation of mro and type members thread safe
Also _PyType_GetMRO and _PyType_GetBases are currently returning borrowed references which aren't safe.
This adds a new header that provides atomic operations on common data
types. The intention is that this will be exposed through Python.h,
although that is not the case yet. The only immediate use is in
the test file.
Co-authored-by: Sam Gross <colesbury@gmail.com>
