diff options
Diffstat (limited to 'src/corelib/thread/qthread.h')
| -rw-r--r-- | src/corelib/thread/qthread.h | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/src/corelib/thread/qthread.h b/src/corelib/thread/qthread.h index 2072e22340..635dd94522 100644 --- a/src/corelib/thread/qthread.h +++ b/src/corelib/thread/qthread.h @@ -161,6 +161,7 @@ private: #if QT_CONFIG(cxx11_future) static QThread *createThreadImpl(std::future<void> &&future); #endif + static Qt::HANDLE currentThreadIdImpl() noexcept Q_DECL_PURE_FUNCTION; friend class QCoreApplication; friend class QThreadData; @@ -236,6 +237,38 @@ QThread *QThread::create(Function &&f) #endif // QT_CONFIG(cxx11_future) +/* + On architectures and platforms we know, interpret the thread control + block (TCB) as a unique identifier for a thread within a process. Otherwise, + fall back to a slower but safe implementation. + + As per the documentation of currentThreadId, we return an opaque handle + as a thread identifier, and application code is not supposed to use that + value for anything. In Qt we use the handle to check if threads are identical, + for which the TCB is sufficient. + + So we use the fastest possible way, rathern than spend time on returning + some pseudo-interoperable value. +*/ +inline Qt::HANDLE QThread::currentThreadId() noexcept +{ + Qt::HANDLE tid; // typedef to void* + Q_STATIC_ASSERT(sizeof(tid) == sizeof(void*)); + // See https://akkadia.org/drepper/tls.pdf for x86 ABI +#if defined(Q_PROCESSOR_X86_32) && defined(Q_OS_LINUX) // x86 32-bit always uses GS + __asm__("movl %%gs:0, %0" : "=r" (tid) : : ); +#elif defined(Q_PROCESSOR_X86_64) && defined(Q_OS_DARWIN64) + // 64bit macOS uses GS, see https://github.com/apple/darwin-xnu/blob/master/libsyscall/os/tsd.h + __asm__("movq %%gs:0, %0" : "=r" (tid) : : ); +#elif defined(Q_PROCESSOR_X86_64) && (defined(Q_OS_LINUX) || defined(Q_OS_FREEBSD)) + // x86_64 Linux, BSD uses FS + __asm__("movq %%fs:0, %0" : "=r" (tid) : : ); +#else + tid = currentThreadIdImpl(); +#endif + return tid; +} + QT_END_NAMESPACE #endif // QTHREAD_H |