# HG changeset patch # User dholmes # Date 1379331493 14400 # Node ID 2e6938dd68f2bf7e8f89db545b594673c740a43e # Parent b135b600a66c1a7e76ff8d1645beab14dd2204af 6900441: PlatformEvent.park(millis) on Linux could still be affected by changes to the time-of-day clock Summary: Associate CLOCK_MONOTONIC with the pthread_cond_t objects used for relative timed waits Reviewed-by: dcubed, shade diff -r b135b600a66c -r 2e6938dd68f2 src/os/linux/vm/os_linux.cpp --- a/src/os/linux/vm/os_linux.cpp Fri Sep 13 16:56:58 2013 -0700 +++ b/src/os/linux/vm/os_linux.cpp Mon Sep 16 07:38:13 2013 -0400 @@ -131,6 +131,7 @@ bool os::Linux::_supports_fast_thread_cpu_time = false; const char * os::Linux::_glibc_version = NULL; const char * os::Linux::_libpthread_version = NULL; +pthread_condattr_t os::Linux::_condattr[1]; static jlong initial_time_count=0; @@ -1399,12 +1400,15 @@ clock_gettime_func(CLOCK_MONOTONIC, &tp) == 0) { // yes, monotonic clock is supported _clock_gettime = clock_gettime_func; + return; } else { // close librt if there is no monotonic clock dlclose(handle); } } } + warning("No monotonic clock was available - timed services may " \ + "be adversely affected if the time-of-day clock changes"); } #ifndef SYS_clock_getres @@ -4709,6 +4713,26 @@ Linux::clock_init(); initial_time_count = os::elapsed_counter(); + + // pthread_condattr initialization for monotonic clock + int status; + pthread_condattr_t* _condattr = os::Linux::condAttr(); + if ((status = pthread_condattr_init(_condattr)) != 0) { + fatal(err_msg("pthread_condattr_init: %s", strerror(status))); + } + // Only set the clock if CLOCK_MONOTONIC is available + if (Linux::supports_monotonic_clock()) { + if ((status = pthread_condattr_setclock(_condattr, CLOCK_MONOTONIC)) != 0) { + if (status == EINVAL) { + warning("Unable to use monotonic clock with relative timed-waits" \ + " - changes to the time-of-day clock may have adverse affects"); + } else { + fatal(err_msg("pthread_condattr_setclock: %s", strerror(status))); + } + } + } + // else it defaults to CLOCK_REALTIME + pthread_mutex_init(&dl_mutex, NULL); // If the pagesize of the VM is greater than 8K determine the appropriate @@ -5519,21 +5543,36 @@ static struct timespec* compute_abstime(timespec* abstime, jlong millis) { if (millis < 0) millis = 0; - struct timeval now; - int status = gettimeofday(&now, NULL); - assert(status == 0, "gettimeofday"); + jlong seconds = millis / 1000; millis %= 1000; if (seconds > 50000000) { // see man cond_timedwait(3T) seconds = 50000000; } - abstime->tv_sec = now.tv_sec + seconds; - long usec = now.tv_usec + millis * 1000; - if (usec >= 1000000) { - abstime->tv_sec += 1; - usec -= 1000000; - } - abstime->tv_nsec = usec * 1000; + + if (os::Linux::supports_monotonic_clock()) { + struct timespec now; + int status = os::Linux::clock_gettime(CLOCK_MONOTONIC, &now); + assert_status(status == 0, status, "clock_gettime"); + abstime->tv_sec = now.tv_sec + seconds; + long nanos = now.tv_nsec + millis * NANOSECS_PER_MILLISEC; + if (nanos >= NANOSECS_PER_SEC) { + abstime->tv_sec += 1; + nanos -= NANOSECS_PER_SEC; + } + abstime->tv_nsec = nanos; + } else { + struct timeval now; + int status = gettimeofday(&now, NULL); + assert(status == 0, "gettimeofday"); + abstime->tv_sec = now.tv_sec + seconds; + long usec = now.tv_usec + millis * 1000; + if (usec >= 1000000) { + abstime->tv_sec += 1; + usec -= 1000000; + } + abstime->tv_nsec = usec * 1000; + } return abstime; } @@ -5625,7 +5664,7 @@ status = os::Linux::safe_cond_timedwait(_cond, _mutex, &abst); if (status != 0 && WorkAroundNPTLTimedWaitHang) { pthread_cond_destroy (_cond); - pthread_cond_init (_cond, NULL) ; + pthread_cond_init (_cond, os::Linux::condAttr()) ; } assert_status(status == 0 || status == EINTR || status == ETIME || status == ETIMEDOUT, @@ -5726,32 +5765,50 @@ static void unpackTime(timespec* absTime, bool isAbsolute, jlong time) { assert (time > 0, "convertTime"); - - struct timeval now; - int status = gettimeofday(&now, NULL); - assert(status == 0, "gettimeofday"); - - time_t max_secs = now.tv_sec + MAX_SECS; - - if (isAbsolute) { - jlong secs = time / 1000; - if (secs > max_secs) { - absTime->tv_sec = max_secs; + time_t max_secs = 0; + + if (!os::Linux::supports_monotonic_clock() || isAbsolute) { + struct timeval now; + int status = gettimeofday(&now, NULL); + assert(status == 0, "gettimeofday"); + + max_secs = now.tv_sec + MAX_SECS; + + if (isAbsolute) { + jlong secs = time / 1000; + if (secs > max_secs) { + absTime->tv_sec = max_secs; + } else { + absTime->tv_sec = secs; + } + absTime->tv_nsec = (time % 1000) * NANOSECS_PER_MILLISEC; + } else { + jlong secs = time / NANOSECS_PER_SEC; + if (secs >= MAX_SECS) { + absTime->tv_sec = max_secs; + absTime->tv_nsec = 0; + } else { + absTime->tv_sec = now.tv_sec + secs; + absTime->tv_nsec = (time % NANOSECS_PER_SEC) + now.tv_usec*1000; + if (absTime->tv_nsec >= NANOSECS_PER_SEC) { + absTime->tv_nsec -= NANOSECS_PER_SEC; + ++absTime->tv_sec; // note: this must be <= max_secs + } + } } - else { - absTime->tv_sec = secs; - } - absTime->tv_nsec = (time % 1000) * NANOSECS_PER_MILLISEC; - } - else { + } else { + // must be relative using monotonic clock + struct timespec now; + int status = os::Linux::clock_gettime(CLOCK_MONOTONIC, &now); + assert_status(status == 0, status, "clock_gettime"); + max_secs = now.tv_sec + MAX_SECS; jlong secs = time / NANOSECS_PER_SEC; if (secs >= MAX_SECS) { absTime->tv_sec = max_secs; absTime->tv_nsec = 0; - } - else { + } else { absTime->tv_sec = now.tv_sec + secs; - absTime->tv_nsec = (time % NANOSECS_PER_SEC) + now.tv_usec*1000; + absTime->tv_nsec = (time % NANOSECS_PER_SEC) + now.tv_nsec; if (absTime->tv_nsec >= NANOSECS_PER_SEC) { absTime->tv_nsec -= NANOSECS_PER_SEC; ++absTime->tv_sec; // note: this must be <= max_secs @@ -5831,15 +5888,19 @@ jt->set_suspend_equivalent(); // cleared by handle_special_suspend_equivalent_condition() or java_suspend_self() + assert(_cur_index == -1, "invariant"); if (time == 0) { - status = pthread_cond_wait (_cond, _mutex) ; + _cur_index = REL_INDEX; // arbitrary choice when not timed + status = pthread_cond_wait (&_cond[_cur_index], _mutex) ; } else { - status = os::Linux::safe_cond_timedwait (_cond, _mutex, &absTime) ; + _cur_index = isAbsolute ? ABS_INDEX : REL_INDEX; + status = os::Linux::safe_cond_timedwait (&_cond[_cur_index], _mutex, &absTime) ; if (status != 0 && WorkAroundNPTLTimedWaitHang) { - pthread_cond_destroy (_cond) ; - pthread_cond_init (_cond, NULL); + pthread_cond_destroy (&_cond[_cur_index]) ; + pthread_cond_init (&_cond[_cur_index], isAbsolute ? NULL : os::Linux::condAttr()); } } + _cur_index = -1; assert_status(status == 0 || status == EINTR || status == ETIME || status == ETIMEDOUT, status, "cond_timedwait"); @@ -5868,17 +5929,24 @@ s = _counter; _counter = 1; if (s < 1) { - if (WorkAroundNPTLTimedWaitHang) { - status = pthread_cond_signal (_cond) ; - assert (status == 0, "invariant") ; + // thread might be parked + if (_cur_index != -1) { + // thread is definitely parked + if (WorkAroundNPTLTimedWaitHang) { + status = pthread_cond_signal (&_cond[_cur_index]); + assert (status == 0, "invariant"); status = pthread_mutex_unlock(_mutex); - assert (status == 0, "invariant") ; - } else { + assert (status == 0, "invariant"); + } else { status = pthread_mutex_unlock(_mutex); - assert (status == 0, "invariant") ; - status = pthread_cond_signal (_cond) ; - assert (status == 0, "invariant") ; - } + assert (status == 0, "invariant"); + status = pthread_cond_signal (&_cond[_cur_index]); + assert (status == 0, "invariant"); + } + } else { + pthread_mutex_unlock(_mutex); + assert (status == 0, "invariant") ; + } } else { pthread_mutex_unlock(_mutex); assert (status == 0, "invariant") ; diff -r b135b600a66c -r 2e6938dd68f2 src/os/linux/vm/os_linux.hpp --- a/src/os/linux/vm/os_linux.hpp Fri Sep 13 16:56:58 2013 -0700 +++ b/src/os/linux/vm/os_linux.hpp Mon Sep 16 07:38:13 2013 -0400 @@ -221,6 +221,13 @@ static jlong fast_thread_cpu_time(clockid_t clockid); + // pthread_cond clock suppport + private: + static pthread_condattr_t _condattr[1]; + + public: + static pthread_condattr_t* condAttr() { return _condattr; } + // Stack repair handling // none present @@ -295,7 +302,7 @@ public: PlatformEvent() { int status; - status = pthread_cond_init (_cond, NULL); + status = pthread_cond_init (_cond, os::Linux::condAttr()); assert_status(status == 0, status, "cond_init"); status = pthread_mutex_init (_mutex, NULL); assert_status(status == 0, status, "mutex_init"); @@ -310,14 +317,19 @@ void park () ; void unpark () ; int TryPark () ; - int park (jlong millis) ; + int park (jlong millis) ; // relative timed-wait only void SetAssociation (Thread * a) { _Assoc = a ; } } ; class PlatformParker : public CHeapObj { protected: + enum { + REL_INDEX = 0, + ABS_INDEX = 1 + }; + int _cur_index; // which cond is in use: -1, 0, 1 pthread_mutex_t _mutex [1] ; - pthread_cond_t _cond [1] ; + pthread_cond_t _cond [2] ; // one for relative times and one for abs. public: // TODO-FIXME: make dtor private ~PlatformParker() { guarantee (0, "invariant") ; } @@ -325,10 +337,13 @@ public: PlatformParker() { int status; - status = pthread_cond_init (_cond, NULL); - assert_status(status == 0, status, "cond_init"); + status = pthread_cond_init (&_cond[REL_INDEX], os::Linux::condAttr()); + assert_status(status == 0, status, "cond_init rel"); + status = pthread_cond_init (&_cond[ABS_INDEX], NULL); + assert_status(status == 0, status, "cond_init abs"); status = pthread_mutex_init (_mutex, NULL); assert_status(status == 0, status, "mutex_init"); + _cur_index = -1; // mark as unused } };