Commit Graph

49 Commits

Author SHA1 Message Date
Brett Simmers be1dfccdf2
gh-118727: Don't drop the GIL in `drop_gil()` unless the current thread holds it (#118745)
`drop_gil()` assumes that its caller is attached, which means that the current
thread holds the GIL if and only if the GIL is enabled, and the enabled-state
of the GIL won't change. This isn't true, though, because `detach_thread()`
calls `_PyEval_ReleaseLock()` after detaching and
`_PyThreadState_DeleteCurrent()` calls it after removing the current thread
from consideration for stop-the-world requests (effectively detaching it).

Fix this by remembering whether or not a thread acquired the GIL when it last
attached, in `PyThreadState._status.holds_gil`, and check this in `drop_gil()`
instead of `gil->enabled`.

This fixes a crash in `test_multiprocessing_pool_circular_import()`, so I've
reenabled it.
2024-05-23 16:59:35 -04:00
Brett Simmers 853163d3b5
gh-116322: Enable the GIL while loading C extension modules (#118560)
Add the ability to enable/disable the GIL at runtime, and use that in
the C module loading code.

We can't know before running a module init function if it supports
free-threading, so the GIL is temporarily enabled before doing so. If
the module declares support for running without the GIL, the GIL is
later disabled. Otherwise, the GIL is permanently enabled, and will
never be disabled again for the life of the current interpreter.
2024-05-06 23:07:23 -04:00
Sam Gross 0e78a545e6
gh-118534: Fix load of `gil->locked` (#118553) 2024-05-03 18:13:40 -04:00
Mark Shannon 39981fd07a
GH-118095: Make sure that progress is made if there are pending calls being handled. (GH-118484) 2024-05-01 22:18:31 +01:00
Sam Gross 5a90de0d4c
gh-116749: Disable GIL by default in free-threaded build (#118295)
Switch GIL to disabled by default in free-threaded build so that the
free-threaded CIs catch thread-safety issues.
2024-04-26 14:22:29 -04:00
Eric Snow 09c2947581
gh-110693: Pending Calls Machinery Cleanups (gh-118296)
This does some cleanup in preparation for later changes.
2024-04-26 01:05:51 +00:00
Victor Stinner 75eed5b373
gh-117929: Restore removed PyEval_InitThreads() function (#117931) 2024-04-17 15:01:28 +02:00
Sam Gross 1f72fb5447
gh-116522: Refactor `_PyThreadState_DeleteExcept` (#117131)
Split `_PyThreadState_DeleteExcept` into two functions:

- `_PyThreadState_RemoveExcept` removes all thread states other than one
  passed as an argument. It returns the removed thread states as a
  linked list.

- `_PyThreadState_DeleteList` deletes those dead thread states. It may
  call destructors, so we want to "start the world" before calling
  `_PyThreadState_DeleteList` to avoid potential deadlocks.
2024-03-21 11:21:02 -07:00
Brett Simmers 9221ef2d8c
gh-116908: Only write to `_pending_calls.calls_to_do` with atomic operations (#117044)
These writes to `pending->calls_to_do` need to be atomic, because other threads
can read (atomically) from `calls_to_do` without holding `pending->mutex`.
2024-03-20 11:18:26 -04:00
Brett Simmers 2731913dd5
gh-116167: Allow disabling the GIL with `PYTHON_GIL=0` or `-X gil=0` (#116338)
In free-threaded builds, running with `PYTHON_GIL=0` will now disable the
GIL. Follow-up issues track work to re-enable the GIL when loading an
incompatible extension, and to disable the GIL by default.

In order to support re-enabling the GIL at runtime, all GIL-related data
structures are initialized as usual, and disabling the GIL simply sets a flag
that causes `take_gil()` and `drop_gil()` to return early.
2024-03-11 11:02:58 -04:00
Nikita Sobolev 817fe33a1d
gh-116590: Fix unused `current_thread_holds_gil` function warning (#116591) 2024-03-11 16:25:04 +03:00
Brett Simmers 0749244d13
gh-112175: Add `eval_breaker` to `PyThreadState` (#115194)
This change adds an `eval_breaker` field to `PyThreadState`. The primary
motivation is for performance in free-threaded builds: with thread-local eval
breakers, we can stop a specific thread (e.g., for an async exception) without
interrupting other threads.

The source of truth for the global instrumentation version is stored in the
`instrumentation_version` field in PyInterpreterState. Threads usually read the
version from their local `eval_breaker`, where it continues to be colocated
with the eval breaker bits.
2024-02-20 09:57:48 -05:00
Sam Gross a3af3cb4f4
gh-110481: Implement inter-thread queue for biased reference counting (#114824)
Biased reference counting maintains two refcount fields in each object:
`ob_ref_local` and `ob_ref_shared`. The true refcount is the sum of these two
fields. In some cases, when refcounting operations are split across threads,
the ob_ref_shared field can be negative (although the total refcount must be
at least zero). In this case, the thread that decremented the refcount
requests that the owning thread give up ownership and merge the refcount
fields.
2024-02-09 17:08:32 -05:00
Andrew Rogers b3f0b698da
gh-104530: Enable native Win32 condition variables by default (GH-104531) 2024-02-02 13:50:51 +00:00
Sam Gross 441affc9e7
gh-111964: Implement stop-the-world pauses (gh-112471)
The `--disable-gil` builds occasionally need to pause all but one thread.  Some
examples include:

* Cyclic garbage collection, where this is often called a "stop the world event"
* Before calling `fork()`, to ensure a consistent state for internal data structures
* During interpreter shutdown, to ensure that daemon threads aren't accessing Python objects

This adds the following functions to implement global and per-interpreter pauses:

* `_PyEval_StopTheWorldAll()` and `_PyEval_StartTheWorldAll()` (for the global runtime)
* `_PyEval_StopTheWorld()` and `_PyEval_StartTheWorld()` (per-interpreter)

(The function names may change.)

These functions are no-ops outside of the `--disable-gil` build.
2024-01-23 11:08:23 -07:00
Sam Gross a3c031884d
gh-112723: Call `PyThreadState_Clear()` from the correct interpreter (#112776)
The `PyThreadState_Clear()` function must only be called with the GIL
held and must be called from the same interpreter as the passed in
thread state. Otherwise, any Python objects on the thread state may be
destroyed using the wrong interpreter, leading to memory corruption.

This is also important for `Py_GIL_DISABLED` builds because free lists
will be associated with PyThreadStates and cleared in
`PyThreadState_Clear()`.

This fixes two places that called `PyThreadState_Clear()` from the wrong
interpreter and adds an assertion to `PyThreadState_Clear()`.
2023-12-12 17:20:21 -07:00
Yan Yanchii fed294c645
gh-112978: Remove redundant condition inside `take_gil` (gh-112979) 2023-12-12 08:23:41 +09:00
Sam Gross cf6110ba13
gh-111924: Use PyMutex for Runtime-global Locks. (gh-112207)
This replaces some usages of PyThread_type_lock with PyMutex, which does not require memory allocation to initialize.

This simplifies some of the runtime initialization and is also one step towards avoiding changing the default raw memory allocator during initialize/finalization, which can be non-thread-safe in some circumstances.
2023-12-07 12:33:40 -07:00
Donghee Na 2dcc57008b
gh-109693: Remove pycore_atomic.h (gh-110992) 2023-10-18 00:33:50 +09:00
Donghee Na 86559ddfec
gh-109693: Update _gil_runtime_state.locked to use pyatomic.h (gh-110836) 2023-10-17 07:32:50 +09:00
Donghee Na 2566434e59
gh-109693: Update _gil_runtime_state.last_holder to use pyatomic.h (#110605) 2023-10-13 10:07:27 +09:00
Donghee Na 67e8d416cc
gh-109693: Use pyatomic.h for signal module (gh-110480) 2023-10-10 08:26:29 +09:00
Eric Snow 7bd560ce8d
gh-76785: Add SendChannel.send_buffer() (#110246)
(This is still a test module.)
2023-10-09 07:39:51 -06:00
Sam Gross 6e97a9647a
gh-109549: Add new states to PyThreadState to support PEP 703 (gh-109915)
This adds a new field 'state' to PyThreadState that can take on one of three values: _Py_THREAD_ATTACHED, _Py_THREAD_DETACHED, or _Py_THREAD_GC.  The "attached" and "detached" states correspond closely to acquiring and releasing the GIL.  The "gc" state is current unused, but will be used to implement stop-the-world GC for --disable-gil builds in the near future.
2023-10-05 09:46:33 -06:00
Mark Shannon bf4bc36069
GH-109369: Merge all eval-breaker flags and monitoring version into one word. (GH-109846) 2023-10-04 16:09:48 +01:00
Eric Snow fd7e08a6f3
gh-76785: Use Pending Calls When Releasing Cross-Interpreter Data (gh-109556)
This fixes some crashes in the _xxinterpchannels module, due to a race between interpreters.
2023-09-19 15:01:34 -06:00
Victor Stinner 517cd82ea7
gh-108987: Fix _thread.start_new_thread() race condition (#109135)
Fix _thread.start_new_thread() race condition. If a thread is created
during Python finalization, the newly spawned thread now exits
immediately instead of trying to access freed memory and lead to a
crash.

thread_run() calls PyEval_AcquireThread() which checks if the thread
must exit. The problem was that tstate was dereferenced earlier in
_PyThreadState_Bind() which leads to a crash most of the time.

Move _PyThreadState_CheckConsistency() from thread_run() to
_PyThreadState_Bind().
2023-09-11 17:27:03 +02:00
Victor Stinner f63d37877a
gh-104690: thread_run() checks for tstate dangling pointer (#109056)
thread_run() of _threadmodule.c now calls
_PyThreadState_CheckConsistency() to check if tstate is a dangling
pointer when Python is built in debug mode.

Rename ceval_gil.c is_tstate_valid() to
_PyThreadState_CheckConsistency() to reuse it in _threadmodule.c.
2023-09-08 11:50:46 +02:00
Victor Stinner a0773b89df
gh-108753: Enhance pystats (#108754)
Statistics gathering is now off by default. Use the "-X pystats"
command line option or set the new PYTHONSTATS environment variable
to 1 to turn statistics gathering on at Python startup.

Statistics are no longer dumped at exit if statistics gathering was
off or statistics have been cleared.

Changes:

* Add PYTHONSTATS environment variable.
* sys._stats_dump() now returns False if statistics are not dumped
  because they are all equal to zero.
* Add PyConfig._pystats member.
* Add tests on sys functions and on setting PyConfig._pystats to 1.
* Add Include/cpython/pystats.h and Include/internal/pycore_pystats.h
  header files.
* Rename '_py_stats' variable to '_Py_stats'.
* Exclude Include/cpython/pystats.h from the Py_LIMITED_API.
* Move pystats.h include from object.h to Python.h.
* Add _Py_StatsOn() and _Py_StatsOff() functions. Remove
  '_py_stats_struct' variable from the API: make it static in
  specialize.c.
* Document API in Include/pystats.h and Include/cpython/pystats.h.
* Complete pystats documentation in Doc/using/configure.rst.
* Don't write "all zeros" stats: if _stats_off() and _stats_clear()
  or _stats_dump() were called.
* _PyEval_Fini() now always call _Py_PrintSpecializationStats() which
  does nothing if stats are all zeros.

Co-authored-by: Michael Droettboom <mdboom@gmail.com>
2023-09-06 15:54:59 +00:00
Mark Shannon e5862113dd
GH-104584: Fix ENTER_EXECUTOR (GH-106141)
* Check eval-breaker in ENTER_EXECUTOR.

* Make sure that frame->prev_instr is set before entering executor.
2023-07-03 21:28:27 +01:00
Victor Stinner 18b1fdebe0
gh-106320: Remove _PyInterpreterState_Get() alias (#106321)
Replace calls to the (removed) slow _PyInterpreterState_Get() with
fast inlined _PyInterpreterState_GET() function.
2023-07-01 23:44:07 +00:00
Eric Snow 757b402ea1
gh-104812: Run Pending Calls in any Thread (gh-104813)
For a while now, pending calls only run in the main thread (in the main interpreter).  This PR changes things to allow any thread run a pending call, unless the pending call was explicitly added for the main thread to run.
2023-06-13 15:02:19 -06:00
Eric Snow 3698fda06e
gh-104341: Call _PyEval_ReleaseLock() with NULL When Finalizing the Current Thread (gh-105109)
This avoids the problematic race in drop_gil() by skipping the FORCE_SWITCHING code there for finalizing threads.

(The idea for this approach came out of discussions with @markshannon.)
2023-06-01 16:24:10 -06:00
Victor Stinner ec0082ca46
gh-105182: Remove PyEval_AcquireLock() and PyEval_InitThreads() (#105183)
Remove functions in the C API:

* PyEval_AcquireLock()
* PyEval_ReleaseLock()
* PyEval_InitThreads()
* PyEval_ThreadsInitialized()

But keep these functions in the stable ABI.

Mention "make regen-limited-abi" in "make regen-all".
2023-06-01 13:41:56 +02:00
Eric Snow 26baa747c2
gh-104341: Adjust tstate_must_exit() to Respect Interpreter Finalization (gh-104437)
With the move to a per-interpreter GIL, this check slipped through the cracks.
2023-05-15 13:59:26 -06:00
Eric Snow 5c9ee498c6
gh-99113: A Per-Interpreter GIL! (gh-104210)
This is the culmination of PEP 684 (and of my 8-year long multi-core Python project)!

Each subinterpreter may now be created with its own GIL (via Py_NewInterpreterFromConfig()).  If not so configured then the interpreter will share with the main interpreter--the status quo since subinterpreters were added decades ago.  The main interpreter always has its own GIL and subinterpreters from Py_NewInterpreter() will always share with the main interpreter.
2023-05-08 13:15:09 -06:00
Eric Snow 92d8bfffbf
gh-99113: Make Sure the GIL is Acquired at the Right Places (gh-104208)
This is a pre-requisite for a per-interpreter GIL.  Without it this change isn't strictly necessary.  However, there is no real downside otherwise.
2023-05-06 15:59:30 -06:00
Nikita Sobolev 6616710731
gh-104233: Fix "unused variable" warning in `ceval_gil.c` (#104234) 2023-05-06 20:28:32 +05:30
Eric Snow f3e7eb48f8
gh-99113: Add PyInterpreterConfig.own_gil (gh-104204)
We also add PyInterpreterState.ceval.own_gil to record if the interpreter actually has its own GIL.

Note that for now we don't actually respect own_gil; all interpreters still share the one GIL.  However, PyInterpreterState.ceval.own_gil does reflect PyInterpreterConfig.own_gil.  That lie is a temporary one that we will fix when the GIL really becomes per-interpreter.
2023-05-05 15:59:20 -06:00
Eric Snow 55671fe047
gh-99113: Share the GIL via PyInterpreterState.ceval.gil (gh-104203)
In preparation for a per-interpreter GIL, we add PyInterpreterState.ceval.gil, set it to the shared GIL for each interpreter, and use that rather than using _PyRuntime.ceval.gil directly.  Note that _PyRuntime.ceval.gil is still the actual GIL.
2023-05-05 13:23:00 -06:00
Victor Stinner 45398ad512
gh-103323: Remove PyRuntimeState_GetThreadState() (#104171)
This function no longer makes sense, since its runtime parameter is
no longer used. Use directly _PyThreadState_GET() and
_PyInterpreterState_GET() instead.
2023-05-04 16:21:01 +02:00
Nikita Sobolev 119f67de08
gh-103167: Fix `-Wstrict-prototypes` warnings by using `(void)` for functions with no args (GH-103168) 2023-04-05 09:22:33 +02:00
Irit Katriel 4c87537efb
gh-102192: Replace PyErr_Fetch/Restore etc by more efficient alternatives (in Python/) (#102193) 2023-02-28 11:50:52 +00:00
Eric Snow e11fc032a7
gh-59956: Clarify Runtime State Status Expectations (gh-101308)
A PyThreadState can be in one of many states in its lifecycle, represented by some status value.  Those statuses haven't been particularly clear, so we're addressing that here.  Specifically:

* made the distinct lifecycle statuses clear on PyThreadState
* identified expectations of how various lifecycle-related functions relate to status
* noted the various places where those expectations don't match the actual behavior

At some point we'll need to address the mismatches.

(This change also includes some cleanup.)

https://github.com/python/cpython/issues/59956
2023-01-30 12:07:48 -07:00
Eric Snow 6036c3e856
gh-59956: Clarify GILState-related Code (gh-101161)
The objective of this change is to help make the GILState-related code easier to understand.  This mostly involves moving code around and some semantically equivalent refactors.  However, there are a also a small number of slight changes in structure and behavior:

* tstate_current is moved out of _PyRuntimeState.gilstate
* autoTSSkey is moved out of _PyRuntimeState.gilstate
* autoTSSkey is initialized earlier
* autoTSSkey is re-initialized (after fork) earlier

https://github.com/python/cpython/issues/59956
2023-01-19 16:04:14 -07:00
Eric Snow 5f55067e23
gh-81057: Move More Globals in Core Code to _PyRuntimeState (gh-99516)
https://github.com/python/cpython/issues/81057
2022-11-16 09:37:14 -07:00
Pablo Galindo Salgado 83eb827247
gh-97922: Run the GC only on eval breaker (#97920) 2022-10-08 07:57:09 -07:00
Victor Stinner 04f4977f50
gh-96387: take_gil() resets drop request before exit (#96869)
At Python exit, sometimes a thread holding the GIL can wait forever
for a thread (usually a daemon thread) which requested to drop the
GIL, whereas the thread already exited. To fix the race condition,
the thread which requested the GIL drop now resets its request before
exiting.

take_gil() now calls RESET_GIL_DROP_REQUEST() before
PyThread_exit_thread() if it called SET_GIL_DROP_REQUEST to fix a
race condition with drop_gil().

Issue discovered and analyzed by Mingliang ZHAO.
2022-09-20 00:13:56 +02:00
Mark Shannon a4a9f2e879
GH-96177: Move GIL and eval breaker code out of ceval.c into ceval_gil.c. (GH-96204) 2022-08-24 14:21:01 +01:00