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QElapsedTimer: remove the runtime check for the monotonic clock

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There is no supported OS with a "maybe" monotonic clock. All of the OSes
we currently support either always have a monotonic clock in the first
place or never have one. There's only one OS in the latter category and
that's INTEGRITY, lacking even the CLOCK_MONOTONIC constant.

Change-Id: Ieec322d73c1e40ad95c8fffd17463531dae2c5bc
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
This commit is contained in:
Thiago Macieira 2023-02-22 09:19:59 -08:00
parent b5fe88a6e5
commit 15d6244ec3
2 changed files with 12 additions and 61 deletions
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65
src/corelib/kernel/qelapsedtimer_unix.cpp
View File

@ -39,13 +39,9 @@ QT_BEGIN_NAMESPACE
* 0 monotonic clock might be supported, runtime check is needed
* >1 (such as 200809L) monotonic clock is always supported
*
* The unixCheckClockType() function will return the clock to use: either
* CLOCK_MONOTONIC or CLOCK_REALTIME. In the case the POSIX option has a value
* of zero, then this function stores a static that contains the clock to be
* used.
*
* There's one extra case, which is when CLOCK_REALTIME isn't defined. When
* that's the case, we'll emulate the clock_gettime function with gettimeofday.
* Since Qt 6.6, we no longer perform any runtime checks and instead enforce
* the use of the monotonic clock in all OSes that have the CLOCK_MONOTONIC
* macro and use of the POSIX realtime clock functions.
*
* Conforming to:
* POSIX.1b-1993 section "Clocks and Timers"
@ -54,59 +50,14 @@ QT_BEGIN_NAMESPACE
* see http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_getres.html
*/
#if !defined(CLOCK_REALTIME)
# define CLOCK_REALTIME 0
static inline void qt_clock_gettime(int, struct timespec *ts)
static constexpr clockid_t regularClock()
{
// support clock_gettime with gettimeofday
struct timeval tv;
gettimeofday(&tv, 0);
ts->tv_sec = tv.tv_sec;
ts->tv_nsec = tv.tv_usec * 1000;
}
static inline int regularClock()
{
return 0;
}
#else
static inline void qt_clock_gettime(clockid_t clock, struct timespec *ts)
{
clock_gettime(clock, ts);
}
static inline clock_t regularClockCheck()
{
struct timespec regular_clock_resolution;
int r = -1;
# ifdef CLOCK_MONOTONIC
// try the monotonic clock
r = clock_getres(CLOCK_MONOTONIC, &regular_clock_resolution);
# ifdef Q_OS_LINUX
// Despite glibc claiming that we should check at runtime, the Linux kernel
// always supports the monotonic clock
Q_ASSERT(r == 0);
#ifdef CLOCK_MONOTONIC
return CLOCK_MONOTONIC;
# endif
if (r == 0)
return CLOCK_MONOTONIC;
# endif
// no monotonic, try the realtime clock
r = clock_getres(CLOCK_REALTIME, &regular_clock_resolution);
Q_ASSERT(r == 0);
#else
return CLOCK_REALTIME;
}
static inline clock_t regularClock()
{
static const clock_t clock = regularClockCheck();
return clock;
}
#endif
}
bool QElapsedTimer::isMonotonic() noexcept
{
@ -121,7 +72,7 @@ QElapsedTimer::ClockType QElapsedTimer::clockType() noexcept
static inline void do_gettime(qint64 *sec, qint64 *frac)
{
timespec ts;
qt_clock_gettime(regularClock(), &ts);
clock_gettime(regularClock(), &ts);
*sec = ts.tv_sec;
*frac = ts.tv_nsec;
}

8
src/corelib/thread/qwaitcondition_unix.cpp
View File

@ -44,13 +44,13 @@ void qt_initialize_pthread_cond(pthread_cond_t *cond, const char *where)
pthread_condattr_t condattr;
pthread_condattr_init(&condattr);
#if (_POSIX_MONOTONIC_CLOCK-0 >= 0)
#ifdef CLOCK_MONOTONIC
#if defined(Q_OS_ANDROID)
if (local_condattr_setclock && QElapsedTimer::clockType() == QElapsedTimer::MonotonicClock)
if (local_condattr_setclock)
local_condattr_setclock(&condattr, CLOCK_MONOTONIC);
#elif !defined(Q_OS_DARWIN)
if (QElapsedTimer::clockType() == QElapsedTimer::MonotonicClock)
pthread_condattr_setclock(&condattr, CLOCK_MONOTONIC);
// Darwin doesn't have this function
pthread_condattr_setclock(&condattr, CLOCK_MONOTONIC);
#endif
#endif
report_error(pthread_cond_init(cond, &condattr), where, "cv init");