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https://issues.apache.org/jira/browse/IMPALA-6449?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael Ho resolved IMPALA-6449.
--------------------------------
Resolution: Fixed
Fix Version/s: Impala 2.12.0
Impala 3.0
https://github.com/apache/impala/commit/30c0375ed358f8040d28fe756a17c6e3965177b1
IMPALA-6449: Use CLOCK_MONOTONIC in ConditionVariable
ConditionVariable is a thin wrapper around pthread_cond_*.
Currently, pthread_cond_timedwait() uses the default attribute
CLOCK_REALTIME. This is susceptible to adjustment to the system
clock from various sources such as NTP and time may go backward.
This change fixes the problem by switching to using CLOCK_MONOTONIC
so time will be monotonic although the frequency of the clock ticks
may still be adjusted by NTP. Ideally, we should use CLOCK_MONOTONIC_RAW
but it's available only on Linux kernel 2.6.28 or latter. This change
also get rids of some usage of boost::get_system_time() which suffers
from the same problem.
Change-Id: I81611cfd5e7c5347203fe7fa6b0f615602257f87
Reviewed-on: http://gerrit.cloudera.org:8080/9158
Reviewed-by: Michael Ho <k...@cloudera.com>
Tested-by: Impala Public Jenkins
> Use CLOCK_MONOTONIC in ConditonVariable
> ---------------------------------------
>
> Key: IMPALA-6449
> URL: https://issues.apache.org/jira/browse/IMPALA-6449
> Project: IMPALA
> Issue Type: Bug
> Components: Backend
> Affects Versions: Impala 2.7.0, Impala 2.8.0, Impala 2.9.0, Impala 2.10.0,
> Impala 2.11.0, Impala 2.12.0
> Reporter: Michael Ho
> Assignee: Michael Ho
> Priority: Minor
> Fix For: Impala 3.0, Impala 2.12.0
>
>
> There are various places in the code which call
> {{ConditionVariable::WaitUntil()}} or {{ConditionVariable::WaitFor()}} with a
> time computed from {{boost::get_system_time()}}.
> {noformat}
> template <typename duration_type>
> bool WaitFor(boost::unique_lock<boost::mutex>& lock,
> const duration_type& wait_duration) {
> return WaitUntil(lock, to_timespec(boost::get_system_time() +
> wait_duration));
> }
> {noformat}
> blocking-queue.h:
> {noformat}
> template <typename V>
> bool BlockingPutWithTimeout(V&& val, int64_t timeout_micros) {
> MonotonicStopWatch timer;
> boost::unique_lock<boost::mutex> write_lock(put_lock_);
> boost::system_time wtime = boost::get_system_time() +
> boost::posix_time::microseconds(timeout_micros);
> {noformat}
> thrift-server.cc:
> {noformat}
> system_time deadline = get_system_time() +
>
> posix_time::milliseconds(ThriftServer::ThriftServerEventProcessor::TIMEOUT_MS);
> // Loop protects against spurious wakeup. Locks provide necessary fences to
> ensure
> // visibility.
> while (!signal_fired_) {
> // Yields lock and allows supervision thread to continue and signal
> if (!signal_cond_.WaitUntil(lock, deadline)) {
> {noformat}
> The above are susceptible to clock adjustment from various sources such as
> NTP. We should switch to using {{clock_gettime(CLOCK_MONOTONIC, ...)}} for
> such elapsed time measurement.
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