Set some attributes on pthread condattrs

Make them use the monotonic clock if that's available. On Mac, the
monotonic clock is not available -- Qt fakes monotonic support by using
the Mach timebase -- so we need to use gettimeofday.

Change-Id: Iaea0b0c0de1b4802780e2476dc3643b703db392c
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

src/corelib/thread/qmutex_p.h

@@ -70,6 +70,8 @@
 #  define QT_LINUX_FUTEX
 #endif
 
+struct timespec;
+
 QT_BEGIN_NAMESPACE
 
 class QMutexData
@@ -137,6 +139,13 @@ public:
 #endif //QT_LINUX_FUTEX
 
 
+#ifdef Q_OS_UNIX
+// helper functions for qmutex_unix.cpp and qwaitcondition_unix.cpp
+// they are in qwaitcondition_unix.cpp actually
+void qt_initialize_pthread_cond(pthread_cond_t *cond, const char *where);
+void qt_abstime_for_timeout(struct timespec *ts, int timeout);
+#endif
+
 QT_END_NAMESPACE
 
 #endif // QMUTEX_P_H

src/corelib/thread/qmutex_unix.cpp

@@ -42,11 +42,14 @@
 #include "qplatformdefs.h"
 #include "qmutex.h"
 #include "qstring.h"
+#include "qelapsedtimer.h"
 
 #ifndef QT_NO_THREAD
 #include "qatomic.h"
 #include "qmutex_p.h"
 #include <errno.h>
+#include <sys/time.h>
+#include <time.h>
 
 #if defined(Q_OS_VXWORKS) && defined(wakeup)
 #undef wakeup
@@ -64,7 +67,7 @@ QMutexPrivate::QMutexPrivate()
     : wakeup(false)
 {
     report_error(pthread_mutex_init(&mutex, NULL), "QMutex", "mutex init");
-    report_error(pthread_cond_init(&cond, NULL), "QMutex", "cv init");
+    qt_initialize_pthread_cond(&cond, "QMutex");
 }
 
 QMutexPrivate::~QMutexPrivate()
@@ -81,12 +84,8 @@ bool QMutexPrivate::wait(int timeout)
         if (timeout < 0) {
             errorCode = pthread_cond_wait(&cond, &mutex);
         } else {
-            struct timeval tv;
-            gettimeofday(&tv, 0);
             timespec ti;
-            ti.tv_nsec = (tv.tv_usec + (timeout % 1000) * 1000) * 1000;
-            ti.tv_sec = tv.tv_sec + (timeout / 1000) + (ti.tv_nsec / 1000000000);
-            ti.tv_nsec %= 1000000000;
+            qt_abstime_for_timeout(&ti, timeout);
             errorCode = pthread_cond_timedwait(&cond, &mutex, &ti);
         }
         if (errorCode) {

src/corelib/thread/qwaitcondition_unix.cpp

@@ -45,11 +45,15 @@
 #include "qreadwritelock.h"
 #include "qatomic.h"
 #include "qstring.h"
+#include "qelapsedtimer.h"
+#include "private/qcore_unix_p.h"
 
 #include "qmutex_p.h"
 #include "qreadwritelock_p.h"
 
 #include <errno.h>
+#include <sys/time.h>
+#include <time.h>
 
 #ifndef QT_NO_THREAD
 
@@ -61,6 +65,38 @@ static void report_error(int code, const char *where, const char *what)
         qWarning("%s: %s failure: %s", where, what, qPrintable(qt_error_string(code)));
 }
 
+void qt_initialize_pthread_cond(pthread_cond_t *cond, const char *where)
+{
+    pthread_condattr_t condattr;
+
+    pthread_condattr_init(&condattr);
+#if !defined(Q_OS_MAC) && (_POSIX_MONOTONIC_CLOCK-0 >= 0)
+    if (QElapsedTimer::clockType() == QElapsedTimer::MonotonicClock)
+        pthread_condattr_setclock(&condattr, CLOCK_MONOTONIC);
+#endif
+    report_error(pthread_cond_init(cond, &condattr), where, "cv init");
+    pthread_condattr_destroy(&condattr);
+}
+
+void qt_abstime_for_timeout(timespec *ts, int timeout)
+{
+#ifdef Q_OS_MAC
+    // on Mac, qt_gettime() (on qelapsedtimer_mac.cpp) returns ticks related to the Mach absolute time
+    // that doesn't work with pthread
+    // Mac also doesn't have clock_gettime
+    struct timeval tv;
+    gettimeofday(&tv, 0);
+    ts->tv_sec = tv.tv_sec;
+    ts->tv_nsec = tv.tv_usec * 1000;
+#else
+    *ts = qt_gettime();
+#endif
+
+    ts->tv_sec += timeout / 1000;
+    ts->tv_nsec += timeout % 1000 * Q_UINT64_C(1000) * 1000;
+    normalizedTimespec(*ts);
+}
+
 class QWaitConditionPrivate {
 public:
     pthread_mutex_t mutex;
@@ -73,14 +109,8 @@ public:
         int code;
         forever {
             if (time != ULONG_MAX) {
-                struct timeval tv;
-                gettimeofday(&tv, 0);
-
                 timespec ti;
-                ti.tv_nsec = (tv.tv_usec + (time % 1000) * 1000) * 1000;
-                ti.tv_sec = tv.tv_sec + (time / 1000) + (ti.tv_nsec / 1000000000);
-                ti.tv_nsec %= 1000000000;
-
+                qt_abstime_for_timeout(&ti, time);
                 code = pthread_cond_timedwait(&cond, &mutex, &ti);
             } else {
                 code = pthread_cond_wait(&cond, &mutex);
@@ -114,7 +144,7 @@ QWaitCondition::QWaitCondition()
 {
     d = new QWaitConditionPrivate;
     report_error(pthread_mutex_init(&d->mutex, NULL), "QWaitCondition", "mutex init");
-    report_error(pthread_cond_init(&d->cond, NULL), "QWaitCondition", "cv init");
+    qt_initialize_pthread_cond(&d->cond, "QWaitCondition");
     d->waiters = d->wakeups = 0;
 }