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QWaitCondition/Android: remove support for relative time waits 

This actually saves two clock_gettime(CLOCK_MONOTONIC) system calls
(albeit to the vDSO): one inside QDeadlineTimer::remainingTimeNSecs() to
calculate the remaining time from the deadline, then one other inside
pthread_cond_timedwait_relative_np() to calculate the deadline from the
timeout, so it can place the FUTEX_WAIT_BITSET system call.

In fact, I can't find __pthread_cond_timedwait_relative() in the Bionic
source any more. The last reference was removed in 2015, when Bionic
started using FUTEX_WAIT_BITSET. So this commit is just removing dead
code in current Android.

Pick-to: 6.5
Change-Id: Ieec322d73c1e40ad95c8fffd174689c4fcff40ae
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
bb10
Thiago Macieira 2023-02-23 11:09:23 -08:00
parent ccd3f2369a
commit 2a997942db
1 changed files with 0 additions and 24 deletions
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24
src/corelib/thread/qwaitcondition_unix.cpp
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@ -22,17 +22,6 @@
QT_BEGIN_NAMESPACE
#ifdef Q_OS_ANDROID
// pthread_condattr_setclock is available only since Android 5.0. On older versions, there's
// a private function for relative waits (hidden in 5.0).
// Use weakref so we can determine at runtime whether each of them is present.
static int local_condattr_setclock(pthread_condattr_t*, clockid_t)
__attribute__((weakref("pthread_condattr_setclock")));
static int local_cond_timedwait_relative(pthread_cond_t*, pthread_mutex_t *, const timespec *)
__attribute__((weakref("__pthread_cond_timedwait_relative")));
#endif
static void report_error(int code, const char *where, const char *what)
{
if (code != 0)
@ -49,12 +38,7 @@ void qt_initialize_pthread_cond(pthread_cond_t *cond, const char *where)
pthread_condattr_init(&condattr);
auto destroy = qScopeGuard([&] { pthread_condattr_destroy(&condattr); });
#if defined(Q_OS_ANDROID)
if (local_condattr_setclock)
local_condattr_setclock(&condattr, CLOCK_MONOTONIC);
#else
pthread_condattr_setclock(&condattr, CLOCK_MONOTONIC);
#endif
#endif
report_error(pthread_cond_init(cond, attrp), where, "cv init");
@ -91,14 +75,6 @@ public:
int wait_relative(QDeadlineTimer deadline)
{
timespec ti;
#ifdef Q_OS_ANDROID
if (!local_condattr_setclock && local_cond_timedwait_relative) {
qint64 nsec = deadline.remainingTimeNSecs();
ti.tv_sec = nsec / (1000 * 1000 * 1000);
ti.tv_nsec = nsec - ti.tv_sec * 1000 * 1000 * 1000;
return local_cond_timedwait_relative(&cond, &mutex, &ti);
}
#endif
qt_abstime_for_timeout(&ti, deadline);
return pthread_cond_timedwait(&cond, &mutex, &ti);
}