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bpo-32243: Use monotonic clock for thread timeouts; more flexibility for very small switch intervals #4964

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bpo-32243: Use monotonic clock for thread timeouts; more flexibility for very small switch intervals #4964

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3497cc8
Attempt at adapting Victor's patch from https://bugs.python.org/issue…
embray Dec 7, 2017
523e89d
In PyCOND_TIMEDWAIT dynamically increase the timeout from the request…
embray Dec 21, 2017
4432ff8
don't define MONOTONIC unless we have pthread_condattr_setclock
embray Jan 31, 2019
5b248ad
update configure
embray Jan 31, 2019
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Attempt at adapting Victor's patch from https://bugs.python.org/issue… 
…23428
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@embray
embray committed Jan 31, 2019
commit 3497cc848ee1cb995f048e9f8b69071d6cfb459a
4 changes: 2 additions & 2 deletions Makefile.pre.in
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Original file line number Diff line number Diff line change
Expand Up @@ -939,7 +939,7 @@ regen-opcode-targets:
$(srcdir)/Python/opcode_targets.h.new
$(UPDATE_FILE) $(srcdir)/Python/opcode_targets.h $(srcdir)/Python/opcode_targets.h.new

Python/ceval.o: $(srcdir)/Python/opcode_targets.h $(srcdir)/Python/ceval_gil.h
Python/ceval.o: $(srcdir)/Python/opcode_targets.h $(srcdir)/Python/ceval_gil.h $(srcdir)/Python/condvar.h

Python/frozen.o: $(srcdir)/Python/importlib.h $(srcdir)/Python/importlib_external.h \
$(srcdir)/Python/importlib_zipimport.h
Expand Down Expand Up @@ -1838,7 +1838,7 @@ patchcheck: @DEF_MAKE_RULE@

# Dependencies

Python/thread.o: @THREADHEADERS@
Python/thread.o: @THREADHEADERS@ $(srcdir)/Python/condvar.h

# Declare targets that aren't real files
.PHONY: all build_all sharedmods check-clean-src oldsharedmods test quicktest
Expand Down
51 changes: 31 additions & 20 deletions Python/condvar.h
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Expand Up @@ -48,44 +48,55 @@
* POSIX support
*/

#define PyCOND_ADD_MICROSECONDS(tv, interval) \
do { /* TODO: add overflow and truncation checks */ \
tv.tv_usec += (long) interval; \
tv.tv_sec += tv.tv_usec / 1000000; \
tv.tv_usec %= 1000000; \
} while (0)

/* We assume all modern POSIX systems have gettimeofday() */
#ifdef GETTIMEOFDAY_NO_TZ
#define PyCOND_GETTIMEOFDAY(ptv) gettimeofday(ptv)
#else
#define PyCOND_GETTIMEOFDAY(ptv) gettimeofday(ptv, (struct timezone *)NULL)
#endif
#include <pthread.h>

/* The following functions return 0 on success, nonzero on error */
#define PyMUTEX_INIT(mut) pthread_mutex_init((mut), NULL)
#define PyMUTEX_FINI(mut) pthread_mutex_destroy(mut)
#define PyMUTEX_LOCK(mut) pthread_mutex_lock(mut)
#define PyMUTEX_UNLOCK(mut) pthread_mutex_unlock(mut)

#define PyCOND_INIT(cond) pthread_cond_init((cond), NULL)
#define PyCOND_T pthread_cond_t
#define PyCOND_FINI(cond) pthread_cond_destroy(cond)
#define PyCOND_SIGNAL(cond) pthread_cond_signal(cond)
#define PyCOND_BROADCAST(cond) pthread_cond_broadcast(cond)
#define PyCOND_WAIT(cond, mut) pthread_cond_wait((cond), (mut))

#define MONOTONIC

Py_LOCAL_INLINE(int)
PyCOND_INIT(PyCOND_T *cond)
{
pthread_condattr_t attr;
int err;

(void)pthread_condattr_init(&attr);
#ifdef MONOTONIC
err = pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);
if (err)
return err;
#endif
err = pthread_cond_init(cond, &attr);
(void)pthread_condattr_destroy(&attr);
return err;
}

/* return 0 for success, 1 on timeout, -1 on error */
Py_LOCAL_INLINE(int)
PyCOND_TIMEDWAIT(PyCOND_T *cond, PyMUTEX_T *mut, long long us)
PyCOND_TIMEDWAIT(PyCOND_T *cond, PyMUTEX_T *mut, PY_TIMEOUT_T us)
{
int r;
struct timespec ts;
struct timeval deadline;
_PyTime_t deadline;

#ifdef MONOTONIC
deadline = _PyTime_GetMonotonicClock();
#else
deadline = _PyTime_GetSystemClock();
#endif

PyCOND_GETTIMEOFDAY(&deadline);
PyCOND_ADD_MICROSECONDS(deadline, us);
ts.tv_sec = deadline.tv_sec;
ts.tv_nsec = deadline.tv_usec * 1000;
deadline += _PyTime_FromNanoseconds(us * 1000);
_PyTime_AsTimespec(deadline, &ts);

r = pthread_cond_timedwait((cond), (mut), &ts);
if (r == ETIMEDOUT)
Expand Down
31 changes: 15 additions & 16 deletions Python/thread_pthread.h
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Original file line number Diff line number Diff line change
Expand Up @@ -74,6 +74,7 @@
defined(HAVE_SEM_TIMEDWAIT))
# define USE_SEMAPHORES
#else
# define MONOTONIC
# undef USE_SEMAPHORES
#endif

Expand All @@ -89,24 +90,16 @@
# define SET_THREAD_SIGMASK sigprocmask
#endif


/* We assume all modern POSIX systems have gettimeofday() */
#ifdef GETTIMEOFDAY_NO_TZ
#define GETTIMEOFDAY(ptv) gettimeofday(ptv)
#ifdef MONOTONIC
#define GETTIME _PyTime_GetMonotonicClock
#else
#define GETTIMEOFDAY(ptv) gettimeofday(ptv, (struct timezone *)NULL)
#define GETTIME _PyTime_GetSystemClock
#endif

#define MICROSECONDS_TO_TIMESPEC(microseconds, ts) \
#define MICROSECONDS_TO_TIMESPEC(us, ts) \
do { \
struct timeval tv; \
GETTIMEOFDAY(&tv); \
tv.tv_usec += microseconds % 1000000; \
tv.tv_sec += microseconds / 1000000; \
tv.tv_sec += tv.tv_usec / 1000000; \
tv.tv_usec %= 1000000; \
ts.tv_sec = tv.tv_sec; \
ts.tv_nsec = tv.tv_usec * 1000; \
_PyTime_t t = GETTIME() + _PyTime_FromNanoseconds(us * 1000); \
_PyTime_AsTimespec(t, &ts); \
} while(0)


Expand Down Expand Up @@ -452,6 +445,7 @@ PyThread_allocate_lock(void)
{
pthread_lock *lock;
int status, error = 0;
pthread_condattr_t attr;

dprintf(("PyThread_allocate_lock called\n"));
if (!initialized)
Expand All @@ -472,9 +466,14 @@ PyThread_allocate_lock(void)
will cause errors. */
_Py_ANNOTATE_PURE_HAPPENS_BEFORE_MUTEX(&lock->mut);

status = pthread_cond_init(&lock->lock_released,
pthread_condattr_default);
pthread_condattr_init(&attr);
#ifdef MONOTONIC
status = pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);
CHECK_STATUS_PTHREAD("pthread_condattr_setclock");
#endif
status = pthread_cond_init(&lock->lock_released, &attr);
CHECK_STATUS_PTHREAD("pthread_cond_init");
pthread_condattr_destroy(&attr);

if (error) {
PyMem_RawFree((void *)lock);
Expand Down