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changeset: 4744:fd506dce728a
user: dholmes
date: Thu Oct 03 18:41:44 2013 -0400
summary: 6900441: PlatformEvent.park(millis) on Linux could still be affected by changes to the time-of-day clock
diff -r c50928ab9548 -r fd506dce728a src/os/linux/vm/os_linux.cpp
--- a/src/os/linux/vm/os_linux.cpp Thu Oct 03 06:04:42 2013 -0700
+++ b/src/os/linux/vm/os_linux.cpp Thu Oct 03 18:41:44 2013 -0400
@@ -144,6 +144,7 @@
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;
@@ -1427,12 +1428,15 @@
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
@@ -4493,6 +4497,26 @@
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
@@ -5339,21 +5363,36 @@
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;
}
@@ -5445,7 +5484,7 @@
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,
@@ -5546,32 +5585,50 @@
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
@@ -5650,16 +5707,20 @@
OSThreadWaitState osts(thread->osthread(), false /* not Object.wait() */);
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");
@@ -5688,17 +5749,24 @@
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 c50928ab9548 -r fd506dce728a src/os/linux/vm/os_linux.hpp
--- a/src/os/linux/vm/os_linux.hpp Thu Oct 03 06:04:42 2013 -0700
+++ b/src/os/linux/vm/os_linux.hpp Thu Oct 03 18:41:44 2013 -0400
@@ -207,6 +207,13 @@
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
@@ -273,7 +280,7 @@
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");
@@ -288,14 +295,19 @@
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<mtInternal> {
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") ; }
@@ -303,10 +315,13 @@
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
}
};
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