X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/9fc3ad34c5326856aeebf02335244ae315cef688..606b005fb2b535b34d1ca45d2d06ee86718e8b1c:/src/unix/threadpsx.cpp diff --git a/src/unix/threadpsx.cpp b/src/unix/threadpsx.cpp index 1ab453633f..8cebd7d212 100644 --- a/src/unix/threadpsx.cpp +++ b/src/unix/threadpsx.cpp @@ -24,9 +24,7 @@ #pragma implementation "thread.h" #endif -// With simple makefiles, we must ignore the file body if not using -// threads. -#include "wx/setup.h" +#include "wx/defs.h" #if wxUSE_THREADS @@ -47,6 +45,15 @@ #include #endif +#ifdef HAVE_THR_SETCONCURRENCY + #include +#endif + +// we use wxFFile under Linux in GetCPUCount() +#ifdef __LINUX__ + #include "wx/ffile.h" +#endif + // ---------------------------------------------------------------------------- // constants // ---------------------------------------------------------------------------- @@ -128,7 +135,7 @@ static pthread_key_t gs_keySelf; static size_t gs_nThreadsBeingDeleted = 0; // a mutex to protect gs_nThreadsBeingDeleted -static pthread_mutex_t gs_mutexDeleteThread = PTHREAD_MUTEX_INITIALIZER; +static pthread_mutex_t gs_mutexDeleteThread; // and a condition variable which will be signaled when all // gs_nThreadsBeingDeleted will have been deleted @@ -157,8 +164,26 @@ wxMutex::wxMutex() { m_internal = new wxMutexInternal; - pthread_mutex_init(&(m_internal->m_mutex), - (pthread_mutexattr_t*) NULL ); + // support recursive locks like Win32, i.e. a thread can lock a mutex which + // it had itself already locked + // + // but initialization of recursive mutexes is non portable , so try + // several methods +#ifdef HAVE_PTHREAD_MUTEXATTR_T + pthread_mutexattr_t attr; + pthread_mutexattr_init(&attr); + pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE); + + pthread_mutex_init(&(m_internal->m_mutex), &attr); +#elif defined(HAVE_PTHREAD_RECURSIVE_MUTEX_INITIALIZER) + // we can use this only as initializer so we have to assign it first to a + // temp var - assigning directly to m_mutex wouldn't even compile + pthread_mutex_t mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP; + m_internal->m_mutex = mutex; +#else // no recursive mutexes + pthread_mutex_init(&(m_internal->m_mutex), NULL); +#endif // HAVE_PTHREAD_MUTEXATTR_T/... + m_locked = 0; } @@ -226,9 +251,12 @@ wxMutexError wxMutex::Unlock() // wxCondition (Posix implementation) //-------------------------------------------------------------------- -// notice that we must use a mutex with POSIX condition variables to ensure -// that the worker thread doesn't signal condition before the waiting thread -// starts to wait for it +// The native POSIX condition variables are dumb: if the condition is signaled +// before another thread starts to wait on it, the signal is lost and so this +// other thread will be never woken up. It's much more convenient to us to +// remember that the condition was signaled and to return from Wait() +// immediately in this case (this is more like Win32 automatic event objects) + class wxConditionInternal { public: @@ -241,20 +269,34 @@ public: void Signal(); void Broadcast(); + void WaitDone(); + bool ShouldWait(); + bool HasWaiters(); + private: - pthread_mutex_t m_mutex; - pthread_cond_t m_condition; + bool m_wasSignaled; // TRUE if condition was signaled while + // nobody waited for it + size_t m_nWaiters; // TRUE if someone already waits for us + + pthread_mutex_t m_mutexProtect; // protects access to vars above + + pthread_mutex_t m_mutex; // the mutex used with the condition + pthread_cond_t m_condition; // the condition itself }; wxConditionInternal::wxConditionInternal() { + m_wasSignaled = FALSE; + m_nWaiters = 0; + if ( pthread_cond_init(&m_condition, (pthread_condattr_t *)NULL) != 0 ) { // this is supposed to never happen wxFAIL_MSG( _T("pthread_cond_init() failed") ); } - if ( pthread_mutex_init(&m_mutex, (pthread_mutexattr_t*)NULL) != 0 ) + if ( pthread_mutex_init(&m_mutex, (pthread_mutexattr_t *)NULL) != 0 || + pthread_mutex_init(&m_mutexProtect, NULL) != 0 ) { // neither this wxFAIL_MSG( _T("wxCondition: pthread_mutex_init() failed") ); @@ -281,60 +323,131 @@ wxConditionInternal::~wxConditionInternal() wxLogDebug(_T("wxCondition: failed to unlock the mutex")); } - if ( pthread_mutex_destroy( &m_mutex ) != 0 ) + if ( pthread_mutex_destroy( &m_mutex ) != 0 || + pthread_mutex_destroy( &m_mutexProtect ) != 0 ) { wxLogDebug(_T("Failed to destroy mutex (it is probably locked)")); } } +void wxConditionInternal::WaitDone() +{ + MutexLock lock(m_mutexProtect); + + m_wasSignaled = FALSE; + m_nWaiters--; +} + +bool wxConditionInternal::ShouldWait() +{ + MutexLock lock(m_mutexProtect); + + if ( m_wasSignaled ) + { + // the condition was signaled before we started to wait, reset the + // flag and return + m_wasSignaled = FALSE; + + return FALSE; + } + + // we start to wait for it + m_nWaiters++; + + return TRUE; +} + +bool wxConditionInternal::HasWaiters() +{ + MutexLock lock(m_mutexProtect); + + if ( m_nWaiters ) + { + // someone waits for us, signal the condition normally + return TRUE; + } + + // nobody waits for us and may be never will - so just remember that the + // condition was signaled and don't do anything else + m_wasSignaled = TRUE; + + return FALSE; +} + void wxConditionInternal::Wait() { - if ( pthread_cond_wait( &m_condition, &m_mutex ) != 0 ) + if ( ShouldWait() ) { - // not supposed to ever happen - wxFAIL_MSG( _T("pthread_cond_wait() failed") ); + if ( pthread_cond_wait( &m_condition, &m_mutex ) != 0 ) + { + // not supposed to ever happen + wxFAIL_MSG( _T("pthread_cond_wait() failed") ); + } } + + WaitDone(); } bool wxConditionInternal::WaitWithTimeout(const timespec* ts) { - switch ( pthread_cond_timedwait( &m_condition, &m_mutex, ts ) ) + bool ok; + + if ( ShouldWait() ) { - case 0: - // condition signaled - return TRUE; + switch ( pthread_cond_timedwait( &m_condition, &m_mutex, ts ) ) + { + case 0: + // condition signaled + ok = TRUE; + break; - default: - wxLogDebug(_T("pthread_cond_timedwait() failed")); + default: + wxLogDebug(_T("pthread_cond_timedwait() failed")); - // fall through + // fall through - case ETIMEDOUT: - case EINTR: - // wait interrupted or timeout elapsed - return FALSE; + case ETIMEDOUT: + case EINTR: + // wait interrupted or timeout elapsed + ok = FALSE; + } + } + else + { + // the condition had already been signaled before + ok = TRUE; } + + WaitDone(); + + return ok; } void wxConditionInternal::Signal() { - MutexLock lock(m_mutex); - - if ( pthread_cond_signal( &m_condition ) != 0 ) + if ( HasWaiters() ) { - // shouldn't ever happen - wxFAIL_MSG(_T("pthread_cond_signal() failed")); + MutexLock lock(m_mutex); + + if ( pthread_cond_signal( &m_condition ) != 0 ) + { + // shouldn't ever happen + wxFAIL_MSG(_T("pthread_cond_signal() failed")); + } } } void wxConditionInternal::Broadcast() { - MutexLock lock(m_mutex); - - if ( pthread_cond_broadcast( &m_condition ) != 0 ) + if ( HasWaiters() ) { - // shouldn't ever happen - wxFAIL_MSG(_T("pthread_cond_broadcast() failed")); + MutexLock lock(m_mutex); + + if ( pthread_cond_broadcast( &m_condition ) != 0 ) + { + // shouldn't ever happen + wxFAIL_MSG(_T("pthread_cond_broadcast() failed")); + } } } @@ -398,6 +511,8 @@ public: void Wait(); // wake up threads waiting for our termination void SignalExit(); + // wake up threads waiting for our start + void SignalRun() { m_condRun.Signal(); } // go to sleep until Resume() is called void Pause(); // resume the thread @@ -420,8 +535,16 @@ public: void SetExitCode(wxThread::ExitCode exitcode) { m_exitcode = exitcode; } wxThread::ExitCode GetExitCode() const { return m_exitcode; } + // the pause flag + void SetReallyPaused(bool paused) { m_isPaused = paused; } + bool IsReallyPaused() const { return m_isPaused; } + // tell the thread that it is a detached one - void Detach() { m_shouldBeJoined = m_shouldBroadcast = FALSE; } + void Detach() + { + m_shouldBeJoined = m_shouldBroadcast = FALSE; + m_isDetached = TRUE; + } // but even detached threads need to notifyus about their termination // sometimes - tell the thread that it should do it void Notify() { m_shouldBroadcast = TRUE; } @@ -434,6 +557,9 @@ private: // this flag is set when the thread should terminate bool m_cancelled; + // this flag is set when the thread is blocking on m_condSuspend + bool m_isPaused; + // the thread exit code - only used for joinable (!detached) threads and // is only valid after the thread termination wxThread::ExitCode m_exitcode; @@ -443,6 +569,7 @@ private: wxCriticalSection m_csJoinFlag; bool m_shouldBeJoined; bool m_shouldBroadcast; + bool m_isDetached; // VZ: it's possible that we might do with less than three different // condition objects - for example, m_condRun and m_condEnd a priori @@ -481,6 +608,10 @@ void *wxThreadInternal::PthreadStart(void *ptr) return (void *)-1; } + // have to declare this before pthread_cleanup_push() which defines a + // block! + bool dontRunAtAll; + #if HAVE_THREAD_CLEANUP_FUNCTIONS // install the cleanup handler which will be called if the thread is // cancelled @@ -490,22 +621,34 @@ void *wxThreadInternal::PthreadStart(void *ptr) // wait for the condition to be signaled from Run() pthread->m_condRun.Wait(); - // call the main entry - pthread->m_exitcode = thread->Entry(); + // test whether we should run the run at all - may be it was deleted + // before it started to Run()? + { + wxCriticalSectionLocker lock(thread->m_critsect); - wxLogTrace(TRACE_THREADS, _T("Thread %ld left its Entry()."), - pthread->GetId()); + dontRunAtAll = pthread->GetState() == STATE_NEW && + pthread->WasCancelled(); + } + if ( !dontRunAtAll ) { - wxCriticalSectionLocker lock(thread->m_critsect); + // call the main entry + pthread->m_exitcode = thread->Entry(); - wxLogTrace(TRACE_THREADS, _T("Thread %ld changes state to EXITED."), + wxLogTrace(TRACE_THREADS, _T("Thread %ld left its Entry()."), pthread->GetId()); - // change the state of the thread to "exited" so that PthreadCleanup - // handler won't do anything from now (if it's called before we do - // pthread_cleanup_pop below) - pthread->SetState(STATE_EXITED); + { + wxCriticalSectionLocker lock(thread->m_critsect); + + wxLogTrace(TRACE_THREADS, _T("Thread %ld changes state to EXITED."), + pthread->GetId()); + + // change the state of the thread to "exited" so that + // PthreadCleanup handler won't do anything from now (if it's + // called before we do pthread_cleanup_pop below) + pthread->SetState(STATE_EXITED); + } } // NB: at least under Linux, pthread_cleanup_push/pop are macros and pop @@ -516,12 +659,21 @@ void *wxThreadInternal::PthreadStart(void *ptr) pthread_cleanup_pop(FALSE); #endif // HAVE_THREAD_CLEANUP_FUNCTIONS - // terminate the thread - thread->Exit(pthread->m_exitcode); + if ( dontRunAtAll ) + { + delete thread; - wxFAIL_MSG(wxT("wxThread::Exit() can't return.")); + return EXITCODE_CANCELLED; + } + else + { + // terminate the thread + thread->Exit(pthread->m_exitcode); + + wxFAIL_MSG(wxT("wxThread::Exit() can't return.")); - return NULL; + return NULL; + } } #if HAVE_THREAD_CLEANUP_FUNCTIONS @@ -558,9 +710,13 @@ wxThreadInternal::wxThreadInternal() m_threadId = 0; m_exitcode = 0; + // set to TRUE only when the thread starts waiting on m_condSuspend + m_isPaused = FALSE; + // defaults for joinable threads m_shouldBeJoined = TRUE; m_shouldBroadcast = TRUE; + m_isDetached = FALSE; } wxThreadInternal::~wxThreadInternal() @@ -572,7 +728,7 @@ wxThreadError wxThreadInternal::Run() wxCHECK_MSG( GetState() == STATE_NEW, wxTHREAD_RUNNING, wxT("thread may only be started once after Create()") ); - m_condRun.Signal(); + SignalRun(); SetState(STATE_RUNNING); @@ -586,26 +742,39 @@ void wxThreadInternal::Wait() if ( wxThread::IsMain() ) wxMutexGuiLeave(); + bool isDetached = m_isDetached; + long id = (long)GetId(); + wxLogTrace(TRACE_THREADS, _T("Starting to wait for thread %ld to exit."), + id); + // wait until the thread terminates (we're blocking in _another_ thread, // of course) m_condEnd.Wait(); - // to avoid memory leaks we should call pthread_join(), but it must only - // be done once - wxCriticalSectionLocker lock(m_csJoinFlag); + wxLogTrace(TRACE_THREADS, _T("Finished waiting for thread %ld."), id); - if ( m_shouldBeJoined ) + // we can't use any member variables any more if the thread is detached + // because it could be already deleted + if ( !isDetached ) { - // FIXME shouldn't we set cancellation type to DISABLED here? If we're - // cancelled inside pthread_join(), things will almost certainly - // break - but if we disable the cancellation, we might deadlock - if ( pthread_join(GetId(), &m_exitcode) != 0 ) + // to avoid memory leaks we should call pthread_join(), but it must + // only be done once + wxCriticalSectionLocker lock(m_csJoinFlag); + + if ( m_shouldBeJoined ) { - wxLogError(_T("Failed to join a thread, potential memory leak " - "detected - please restart the program")); - } + // FIXME shouldn't we set cancellation type to DISABLED here? If + // we're cancelled inside pthread_join(), things will almost + // certainly break - but if we disable the cancellation, we + // might deadlock + if ( pthread_join((pthread_t)id, &m_exitcode) != 0 ) + { + wxLogError(_("Failed to join a thread, potential memory leak " + "detected - please restart the program")); + } - m_shouldBeJoined = FALSE; + m_shouldBeJoined = FALSE; + } } // reacquire GUI mutex @@ -622,6 +791,9 @@ void wxThreadInternal::SignalExit() // wake up all the threads waiting for our termination - if there are any if ( m_shouldBroadcast ) { + wxLogTrace(TRACE_THREADS, _T("Thread %ld signals end condition."), + GetId()); + m_condEnd.Broadcast(); } } @@ -644,10 +816,23 @@ void wxThreadInternal::Resume() wxCHECK_RET( m_state == STATE_PAUSED, wxT("can't resume thread which is not suspended.") ); - wxLogTrace(TRACE_THREADS, _T("Waking up thread %ld"), GetId()); + // the thread might be not actually paused yet - if there were no call to + // TestDestroy() since the last call to Pause() for example + if ( IsReallyPaused() ) + { + wxLogTrace(TRACE_THREADS, _T("Waking up thread %ld"), GetId()); - // wake up Pause() - m_condSuspend.Signal(); + // wake up Pause() + m_condSuspend.Signal(); + + // reset the flag + SetReallyPaused(FALSE); + } + else + { + wxLogTrace(TRACE_THREADS, _T("Thread %ld is not yet really paused"), + GetId()); + } SetState(STATE_RUNNING); } @@ -668,7 +853,9 @@ bool wxThread::IsMain() void wxThread::Yield() { +#ifdef HAVE_SCHED_YIELD sched_yield(); +#endif } void wxThread::Sleep(unsigned long milliseconds) @@ -676,6 +863,63 @@ void wxThread::Sleep(unsigned long milliseconds) wxUsleep(milliseconds); } +int wxThread::GetCPUCount() +{ +#if defined(__LINUX__) && wxUSE_FFILE + // read from proc (can't use wxTextFile here because it's a special file: + // it has 0 size but still can be read from) + wxLogNull nolog; + + wxFFile file(_T("/proc/cpuinfo")); + if ( file.IsOpened() ) + { + // slurp the whole file + wxString s; + if ( file.ReadAll(&s) ) + { + // (ab)use Replace() to find the number of "processor" strings + size_t count = s.Replace(_T("processor"), _T("")); + if ( count > 0 ) + { + return count; + } + + wxLogDebug(_T("failed to parse /proc/cpuinfo")); + } + else + { + wxLogDebug(_T("failed to read /proc/cpuinfo")); + } + } +#elif defined(_SC_NPROCESSORS_ONLN) + // this works for Solaris + int rc = sysconf(_SC_NPROCESSORS_ONLN); + if ( rc != -1 ) + { + return rc; + } +#endif // different ways to get number of CPUs + + // unknown + return -1; +} + +bool wxThread::SetConcurrency(size_t level) +{ +#ifdef HAVE_THR_SETCONCURRENCY + int rc = thr_setconcurrency(level); + if ( rc != 0 ) + { + wxLogSysError(rc, _T("thr_setconcurrency() failed")); + } + + return rc == 0; +#else // !HAVE_THR_SETCONCURRENCY + // ok only for the default value + return level == 0; +#endif // HAVE_THR_SETCONCURRENCY/!HAVE_THR_SETCONCURRENCY +} + // ----------------------------------------------------------------------------- // creating thread // ----------------------------------------------------------------------------- @@ -709,8 +953,18 @@ wxThreadError wxThread::Create() wxLogError(_("Cannot retrieve thread scheduling policy.")); } - int min_prio = sched_get_priority_min(policy), - max_prio = sched_get_priority_max(policy), +#ifdef __VMS__ + /* the pthread.h contains too many spaces. This is a work-around */ +# undef sched_get_priority_max +#undef sched_get_priority_min +#define sched_get_priority_max(_pol_) \ + (_pol_ == SCHED_OTHER ? PRI_FG_MAX_NP : PRI_FIFO_MAX) +#define sched_get_priority_min(_pol_) \ + (_pol_ == SCHED_OTHER ? PRI_FG_MIN_NP : PRI_FIFO_MIN) +#endif + + int max_prio = sched_get_priority_max(policy), + min_prio = sched_get_priority_min(policy), prio = m_internal->GetPriority(); if ( min_prio == -1 || max_prio == -1 ) @@ -862,6 +1116,9 @@ unsigned long wxThread::GetId() const wxThreadError wxThread::Pause() { + wxCHECK_MSG( This() != this, wxTHREAD_MISC_ERROR, + _T("a thread can't pause itself") ); + wxCriticalSectionLocker lock(m_critsect); if ( m_internal->GetState() != STATE_RUNNING ) @@ -871,6 +1128,9 @@ wxThreadError wxThread::Pause() return wxTHREAD_NOT_RUNNING; } + wxLogTrace(TRACE_THREADS, _T("Asking thread %ld to pause."), + GetId()); + // just set a flag, the thread will be really paused only during the next // call to TestDestroy() m_internal->SetState(STATE_PAUSED); @@ -880,20 +1140,17 @@ wxThreadError wxThread::Pause() wxThreadError wxThread::Resume() { - m_critsect.Enter(); + wxCHECK_MSG( This() != this, wxTHREAD_MISC_ERROR, + _T("a thread can't resume itself") ); - wxThreadState state = m_internal->GetState(); + wxCriticalSectionLocker lock(m_critsect); - // the thread might be not actually paused yet - if there were no call to - // TestDestroy() since the last call to Pause(), so avoid that - // TestDestroy() deadlocks trying to enter m_critsect by leaving it before - // calling Resume() - m_critsect.Leave(); + wxThreadState state = m_internal->GetState(); switch ( state ) { case STATE_PAUSED: - wxLogTrace(TRACE_THREADS, _T("Thread %ld is suspended, resuming."), + wxLogTrace(TRACE_THREADS, _T("Thread %ld suspended, resuming."), GetId()); m_internal->Resume(); @@ -931,6 +1188,9 @@ wxThread::ExitCode wxThread::Wait() wxThreadError wxThread::Delete(ExitCode *rc) { + wxCHECK_MSG( This() != this, wxTHREAD_MISC_ERROR, + _T("a thread can't delete itself") ); + m_critsect.Enter(); wxThreadState state = m_internal->GetState(); @@ -950,6 +1210,12 @@ wxThreadError wxThread::Delete(ExitCode *rc) switch ( state ) { case STATE_NEW: + // we need to wake up the thread so that PthreadStart() will + // terminate - right now it's blocking on m_condRun + m_internal->SignalRun(); + + // fall through + case STATE_EXITED: // nothing to do break; @@ -1012,7 +1278,8 @@ wxThreadError wxThread::Kill() #if !HAVE_THREAD_CLEANUP_FUNCTIONS ScheduleThreadForDeletion(); - OnExit(); + // don't call OnExit() here, it can only be called in the + // threads context and we're in the context of another thread DeleteThread(this); #endif // HAVE_THREAD_CLEANUP_FUNCTIONS @@ -1028,6 +1295,10 @@ wxThreadError wxThread::Kill() void wxThread::Exit(ExitCode status) { + wxASSERT_MSG( This() == this, + _T("wxThread::Exit() can only be called in the " + "context of the same thread") ); + // from the moment we call OnExit(), the main program may terminate at any // moment, so mark this thread as being already in process of being // deleted or wxThreadModule::OnExit() will try to delete it again @@ -1072,10 +1343,16 @@ void wxThread::Exit(ExitCode status) // also test whether we were paused bool wxThread::TestDestroy() { + wxASSERT_MSG( This() == this, + _T("wxThread::TestDestroy() can only be called in the " + "context of the same thread") ); + m_critsect.Enter(); if ( m_internal->GetState() == STATE_PAUSED ) { + m_internal->SetReallyPaused(TRUE); + // leave the crit section or the other threads will stop too if they // try to call any of (seemingly harmless) IsXXX() functions while we // sleep @@ -1101,8 +1378,8 @@ wxThread::~wxThread() if ( m_internal->GetState() != STATE_EXITED && m_internal->GetState() != STATE_NEW ) { - wxLogDebug(_T("The thread is being destroyed although it is still " - "running! The application may crash.")); + wxLogDebug(_T("The thread %ld is being destroyed although it is still " + "running! The application may crash."), GetId()); } m_critsect.Leave(); @@ -1112,6 +1389,17 @@ wxThread::~wxThread() // remove this thread from the global array gs_allThreads.Remove(this); + + // detached thread will decrement this counter in DeleteThread(), but it + // is not called for the joinable threads, so do it here + if ( !m_isDetached ) + { + MutexLock lock(gs_mutexDeleteThread); + gs_nThreadsBeingDeleted--; + + wxLogTrace(TRACE_THREADS, _T("%u scheduled for deletion threads left."), + gs_nThreadsBeingDeleted - 1); + } } // ----------------------------------------------------------------------------- @@ -1182,6 +1470,10 @@ bool wxThreadModule::OnInit() gs_mutexGui->Lock(); #endif // wxUSE_GUI + // under Solaris we get a warning from CC when using + // PTHREAD_MUTEX_INITIALIZER, so do it dynamically + pthread_mutex_init(&gs_mutexDeleteThread, NULL); + return TRUE; } @@ -1208,7 +1500,10 @@ void wxThreadModule::OnExit() // terminate any threads left size_t count = gs_allThreads.GetCount(); if ( count != 0u ) - wxLogDebug(wxT("Some threads were not terminated by the application.")); + { + wxLogDebug(wxT("%u threads were not terminated by the application."), + count); + } for ( size_t n = 0u; n < count; n++ ) { @@ -1243,8 +1538,9 @@ static void ScheduleThreadForDeletion() gs_nThreadsBeingDeleted++; - wxLogTrace(TRACE_THREADS, _T("%u threads waiting to be deleted"), - gs_nThreadsBeingDeleted); + wxLogTrace(TRACE_THREADS, _T("%u thread%s waiting to be deleted"), + gs_nThreadsBeingDeleted, + gs_nThreadsBeingDeleted == 1 ? "" : "s"); } static void DeleteThread(wxThread *This) @@ -1263,6 +1559,9 @@ static void DeleteThread(wxThread *This) "one?") ); } + wxLogTrace(TRACE_THREADS, _T("%u scheduled for deletion threads left."), + gs_nThreadsBeingDeleted - 1); + if ( !--gs_nThreadsBeingDeleted ) { // no more threads left, signal it