gh-112535: Implement fallback implementation of _Py_ThreadId() #113185
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I reopened the PR, since there was some accident with #113094 diff --git a/Include/object.h b/Include/object.h
index 6afdc1688e..d31df80db0 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -245,54 +245,7 @@ static inline uintptr_t
_Py_ThreadId(void)
{
uintptr_t tid;
-#if defined(_MSC_VER) && defined(_M_X64)
- tid = __readgsqword(48);
-#elif defined(_MSC_VER) && defined(_M_IX86)
- tid = __readfsdword(24);
-#elif defined(_MSC_VER) && defined(_M_ARM64)
- tid = __getReg(18);
-#elif defined(__i386__)
- __asm__("movl %%gs:0, %0" : "=r" (tid)); // 32-bit always uses GS
-#elif defined(__MACH__) && defined(__x86_64__)
- __asm__("movq %%gs:0, %0" : "=r" (tid)); // x86_64 macOSX uses GS
-#elif defined(__x86_64__)
- __asm__("movq %%fs:0, %0" : "=r" (tid)); // x86_64 Linux, BSD uses FS
-#elif defined(__arm__)
- __asm__ ("mrc p15, 0, %0, c13, c0, 3\nbic %0, %0, #3" : "=r" (tid));
-#elif defined(__aarch64__) && defined(__APPLE__)
- __asm__ ("mrs %0, tpidrro_el0" : "=r" (tid));
-#elif defined(__aarch64__)
- __asm__ ("mrs %0, tpidr_el0" : "=r" (tid));
-#elif defined(__powerpc64__)
- #if defined(__clang__) && _Py__has_builtin(__builtin_thread_pointer)
- tid = (uintptr_t)__builtin_thread_pointer();
- #else
- // r13 is reserved for use as system thread ID by the Power 64-bit ABI.
- register uintptr_t tp __asm__ ("r13");
- __asm__("" : "=r" (tp));
- tid = tp;
- #endif
-#elif defined(__powerpc__)
- #if defined(__clang__) && _Py__has_builtin(__builtin_thread_pointer)
- tid = (uintptr_t)__builtin_thread_pointer();
- #else
- // r2 is reserved for use as system thread ID by the Power 32-bit ABI.
- register uintptr_t tp __asm__ ("r2");
- __asm__ ("" : "=r" (tp));
- tid = tp;
- #endif
-#elif defined(__s390__) && defined(__GNUC__)
- // Both GCC and Clang have supported __builtin_thread_pointer
- // for s390 from long time ago.
- tid = (uintptr_t)__builtin_thread_pointer();
-#elif defined(__riscv)
- #if defined(__clang__) && _Py__has_builtin(__builtin_thread_pointer)
- tid = (uintptr_t)__builtin_thread_pointer();
- #else
- // tp is Thread Pointer provided by the RISC-V ABI.
- __asm__ ("mv %0, tp" : "=r" (tid));
- #endif
-#elif defined(thread_local) || defined(__GNUC__)
+#if defined(thread_local) || defined(__GNUC__)
// gh-112535: Using characteristics of TLS address mapping.
// The address of the thread-local variable is not equal with the actual thread pointer,
// However, it has the property of being determined by loader at runtime, with no duplication of values |
colesbury
approved these changes
Dec 18, 2023
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Some suggestions on code comments below. I think we should put any detailed explanations of _Py_GetThreadLocal_Addr near the implementation (and not where it's called in _Py_ThreadId().
I don't think there's a lot we can say generally about the implementation of &_Py_tss_tstate -- it depends on the platform, but adding a constant offset is generally not expensive. There are two common costs:
- Calling
_Py_GetThreadLocal_Addr(), which mostly can't be inlined. - Depending on the implementation of TLS, computing the address may or may not require another function call.
Include/object.h
Outdated
| @@ -290,6 +292,13 @@ _Py_ThreadId(void) | |||
| // tp is Thread Pointer provided by the RISC-V ABI. | |||
| __asm__ ("mv %0, tp" : "=r" (tid)); | |||
| #endif | |||
| #elif defined(thread_local) || defined(__GNUC__) | |||
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I think this should just be an #else. We're not using thread_local or depending on GNU specific features here in object.h.
Co-authored-by: Sam Gross <colesbury@gmail.com>
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…ythongh-113185) --------- Co-authored-by: Sam Gross <colesbury@gmail.com>
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…ythongh-113185) --------- Co-authored-by: Sam Gross <colesbury@gmail.com>
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…ythongh-113185) --------- Co-authored-by: Sam Gross <colesbury@gmail.com>
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_Py_ThreadId()work on PowerPC, IBM Z, etc. #112535