refactor: Replace boost::mutex,condition_var,chrono with std equivalents in scheduler #18234

pull ajtowns wants to merge 6 commits into bitcoin:master from ajtowns:202002-scheduler-deboost changing 14 files +151 −117
  1. ajtowns commented at 5:09 am on March 1, 2020: member

    Replacing boost functionality with C++11 stuff.

    Motivated by #18227, but should stand alone. Changing from boost::condition_var to std::condition_var means threadGroup.interrupt_all isn’t enough to interrupt serviceQueue anymore, so that means calling stop() before join_all() is needed. And the existing reverselock.h code doesn’t work with sync.h’s DebugLock code (because the reversed lock won’t be removed from g_lockstack which then leads to incorrect potential deadlock warnings), so I’ve replaced that with a dedicated class and macro that’s aware of our debug lock behaviour.

    Fixes #16027, Fixes #14200, Fixes #18227

  2. fanquake added the label Refactoring on Mar 1, 2020
  3. fanquake commented at 5:14 am on March 1, 2020: member
    cc @theuni. I know you have been working on similar refactors recently.
  4. ajtowns force-pushed on Mar 1, 2020
  5. ajtowns force-pushed on Mar 1, 2020
  6. DrahtBot commented at 10:03 am on March 1, 2020: member

    The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

    Conflicts

    Reviewers, this pull request conflicts with the following ones:

    • #18271 (scheduler: Workaround negative nsecs bug in boost’s wait_until by luke-jr)
    • #18264 ([WIP] build: Remove Boost Chrono by fanquake)
    • #16117 (util: Replace boost sleep with std sleep by MarcoFalke)

    If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

  7. in src/sync.h:213 in 3cb2664971 outdated 
    208+        const int line;
209+     };
210+     friend class reverse_lock;
211 };
212 
213+#define REVERSE_LOCK(g) decltype(g)::reverse_lock PASTE2(revlock, __COUNTER__)(g, #g, __FILE__, __LINE__)
    elichai commented at 1:29 pm on March 1, 2020:
    Pending comments on my post here: #18088 (comment) Maybe replace it with PASTE2(revlock,PASTE2(__FILE__,__LINE__))
    ajtowns commented at 1:40 am on March 2, 2020:
    We already use __COUNTER__ for LOCK() in sync.h, so reusing it here seems fine. Using __FILE__ seems unlikely to generate a usable symbol name too :)
  8. in src/sync.cpp:63 in 42a5326a4d outdated 
    59@@ -60,6 +60,11 @@ struct CLockLocation {
60             mutexName, sourceFile, itostr(sourceLine), (fTry ? " (TRY)" : ""), m_thread_name);
61     }
62 
63+    std::string Name() const
    elichai commented at 2:24 pm on March 1, 2020:
    Maybe change to const std::string& Name() so that it will only copy/allocate it if needed?
    MarcoFalke commented at 3:04 pm on March 1, 2020:
    #17198
    elichai commented at 3:10 pm on March 1, 2020:
    oh god. thanks. (for some reason I thought/hoped C++ helps you making sure you’re not violating the lifetime when using references) I think I should stop using Rust lol
  9. practicalswift commented at 8:14 pm on March 1, 2020: contributor

    Concept ACK

    Thanks for working on de-boosting! :)

  10. in src/test/txindex_tests.cpp:75 in 42a5326a4d outdated 
    69@@ -70,9 +70,6 @@ BOOST_FIXTURE_TEST_CASE(txindex_initial_sync, TestChain100Setup)
70     // shutdown sequence (c.f. Shutdown() in init.cpp)
71     txindex.Stop();
72 
73-    threadGroup.interrupt_all();
74-    threadGroup.join_all();
75-
    jonatack commented at 2:22 pm on March 2, 2020:

    In 69460c9 could these be also removed in src/test/transaction_tests.cpp L::457-458 if they are handled with TestingSetup::~TestingSetup(); the test compiles and runs without them.

    0--- a/src/test/transaction_tests.cpp
1+++ b/src/test/transaction_tests.cpp
2@@ -453,9 +453,6 @@ BOOST_AUTO_TEST_CASE(test_big_witness_transaction)
3
4     bool controlCheck = control.Wait();
5     assert(controlCheck);
6-
7-    threadGroup.interrupt_all();
8-    threadGroup.join_all();
9 }
    MarcoFalke commented at 5:08 pm on March 2, 2020:
    Not sure why this should be safe to remove. The scheduler needs to be stopped before this test ends, so the interrupt_all should be replaced by a scheduler.stop(). I think that otherwise you reintroduce bug #15410
    jonatack commented at 5:19 pm on March 2, 2020:
    Thanks. I was just now looking at src/test/checkqueue_tests.cpp which has similar code.
    ajtowns commented at 3:36 am on March 4, 2020:
    @jonatack In transaction_tests, that’s a locally declared threadGroup, and it’s a BasicTestingSetup too, so the TestingSetup destructor wouldn’t execute, and even if it did, wouldn’t clean up that threadGroup. @MarcoFalke Ah, you’re quite right. Have undeleted the code and added a comment.
    jonatack commented at 2:57 pm on March 5, 2020:
    @ajtowns right, makes sense. Thanks for the explanation.
    MarcoFalke commented at 3:00 pm on March 17, 2020:

    in commit 306f71b4eb4a0fd8e64f47dc008bc235b80b13d9:

    After adding the scheduler.stop(), they are again redundant and confusing. I’d suggest to remove the threadGroup calls

    ajtowns commented at 6:32 pm on March 17, 2020:
    Calling stop() doesn’t actually cause the thread to stop, you need to wait for it to complete. Could do that by looping and waiting for AreThreadsServicingQueue() to be false, but that still leaves the possibility you continue on and destruct the object in between --nThreadsServicingQueue; and newTaskScheduled.notify_one(); at the end of serviceQueue. Could drop the interrupt_all but if some other thread in the group needed an interrupt before being joined, that’d cause a hang too… So until we change something else, this doesn’t seem redundant to me?
    MarcoFalke commented at 6:34 pm on March 17, 2020:
    Ups, correct.
  11. jonatack commented at 4:16 pm on March 2, 2020: member
    ACK 42a5326 I reviewed the changes and surrounding code in detail, built/ran tests for each commit, ran bitcoind for 2 days (debian), and shut down/restarted bitcoind several times. This looks good.
  12. theuni commented at 4:30 pm on March 2, 2020: member

    This doesn’t seem to take into account that boost::condition_variable is interruptible, and can’t simply be swapped out. Have I missed some prior work that makes this ok?

    Ok, I see that in the description. Re-reviewing.

  13. theuni commented at 5:03 pm on March 2, 2020: member
    I would’ve expected this to require more work, but it looks like the scheduler was already surprisingly interruptible. Concept ACK. @TheBlueMatt might be aware of more scheduling minefields.
  14. in src/scheduler.cpp:18 in 42a5326a4d outdated 
    14@@ -16,22 +15,14 @@ CScheduler::CScheduler() : nThreadsServicingQueue(0), stopRequested(false), stop
15 
16 CScheduler::~CScheduler()
17 {
18+    LOCK(newTaskMutex);
    theuni commented at 5:50 pm on March 2, 2020:
    Adding a lock in a destructor just for an assertion is a shame. Maybe this should be behind a debug guard?
    ajtowns commented at 5:27 am on March 3, 2020:
    It’s probably not useful in the first place, the lock’s about to be destroyed, so if anyone else even has a reference to it there’s a bug, and threadsafety annotations don’t apply to constructors and destructors for the same reason.
  15. in src/init.cpp:209 in 42a5326a4d outdated 
    206@@ -207,6 +207,7 @@ void Shutdown(NodeContext& node)
207 
208     // After everything has been shut down, but before things get flushed, stop the
209     // CScheduler/checkqueue threadGroup
210+    if (node.scheduler) node.scheduler->stop();
    theuni commented at 6:52 pm on March 2, 2020:
    Are these guaranteed to fully execute in-order? Can an interruption-point hit while the scheduler is still tearing down?
    ajtowns commented at 4:02 am on March 4, 2020:
    Not sure what you’re asking; node.scheduler->stop() just sets a boolean to say “exit the loop” and notifies everything waiting on the condition var to prevent it staying asleep, all the tear down happens in the thread. The interruption could certainly happen while it’s tearing down, stop(); interrupt_all() happen in one thread, and only afterwards does the other thread even wake up. I don’t think boost interrupt will have an effect anymore though, because serviceQueue doesn’t use any boost primitives and boost interrupt only sets a flag which is checked by other boost things.
  16. MarcoFalke renamed this:
    scheduler.cpp: Replace boost::mutex,condition_var,chrono with std equivalents
    refactor: Replace boost::mutex,condition_var,chrono with std equivalents in scheduler
    on Mar 3, 2020
  17. ajtowns force-pushed on Mar 4, 2020
  18. MarcoFalke added this to the "In progress" column in a project
  19. MarcoFalke added this to the milestone 0.20.0 on Mar 5, 2020
  20. MarcoFalke commented at 9:03 pm on March 5, 2020: member

    Should add

    0Fixes [#16027](/bitcoin-bitcoin/16027/), Fixes [#14200](/bitcoin-bitcoin/14200/), Fixes [#18227](/bitcoin-bitcoin/18227/)

    to OP?

  21. fanquake commented at 7:42 am on March 6, 2020: member
    @ajtowns Can you rebase on master now that #16117 is merged. Also, feel free to include a commit here to kill the last DHAVE_WORKING_BOOST_SLEEP_FOR.
  22. DrahtBot added the label Needs rebase on Mar 6, 2020
  23. scheduler: don't rely on boost interrupt on shutdown 
    Calling interrupt_all() will immediately stop the scheduler, so it's
safe to invoke stop() beforehand, and this removes the reliance on boost
to interrupt serviceQueue().
    306f71b4eb
  24. sync.h: add REVERSE_LOCK b9c4260127
  25. scheduler: switch from boost to std 
    Changes from boost::chrono to std::chrono, boost::condition_var to
std::condition_var, boost::mutex to sync.h Mutex, and reverselock.h to
sync.h REVERSE_LOCK. Also adds threadsafety annotations to CScheduler
members.
    d0ebd93270
  26. Drop unused reverselock.h cea19f6859
  27. scheduler_tests: re-enable mockforward test 294937b39d
  28. MarcoFalke removed the label Needs rebase on Mar 6, 2020
  29. MarcoFalke added the label Needs rebase on Mar 6, 2020
  30. lint-cppcheck: Remove -DHAVE_WORKING_BOOST_SLEEP_FOR 70a6b529f3
  31. ajtowns force-pushed on Mar 6, 2020
  32. DrahtBot removed the label Needs rebase on Mar 6, 2020
  33. laanwj commented at 7:08 pm on March 6, 2020: member
    Great work! I’m really glad this is happening, thanks for working on this. ACK 70a6b529f306ff72ea1badf25e970a92b2b17ab3
  34. laanwj merged this on Mar 6, 2020
  35. laanwj closed this on Mar 6, 2020
  36. MarcoFalke moved this from the "In progress" to the "Done" column in a project
  37. in src/sync.cpp:163 in b9c4260127 outdated 
    159@@ -155,6 +160,18 @@ void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs
160     push_lock(cs, CLockLocation(pszName, pszFile, nLine, fTry, util::ThreadGetInternalName()));
161 }
162 
163+void CheckLastCritical(void* cs, std::string& lockname, const char* guardname, const char* file, int line)
    MarcoFalke commented at 3:05 pm on March 17, 2020:

    in commit b9c426012770d166e6ebfab27689be44e6e89aa5:

    Why is this not called GetLastLockName, which better describes what this function does, imo.

  38. in src/sync.h:206 in b9c4260127 outdated 
    201+        reverse_lock(reverse_lock const&);
202+        reverse_lock& operator=(reverse_lock const&);
203+
204+        UniqueLock& lock;
205+        UniqueLock templock;
206+        std::string lockname;
    MarcoFalke commented at 3:09 pm on March 17, 2020:

    in commit b9c426012770d166e6ebfab27689be44e6e89aa5:

    Should be m_lockname. Also for other members?

  39. in src/sync.h:205 in b9c4260127 outdated 
    200+     private:
201+        reverse_lock(reverse_lock const&);
202+        reverse_lock& operator=(reverse_lock const&);
203+
204+        UniqueLock& lock;
205+        UniqueLock templock;
    MarcoFalke commented at 4:40 pm on March 17, 2020:

    in commit b9c426012770d166e6ebfab27689be44e6e89aa5:

    I think it would help readers of the code to briefly explain why this is needed. Also, m_templock? ;)

  40. in src/scheduler.h:10 in d0ebd93270 outdated 
     6@@ -7,11 +7,12 @@
 7 
 8 //
 9 // NOTE:
10-// boost::thread / boost::chrono should be ported to std::thread / std::chrono
11+// boost::thread should be ported to std::thread
    MarcoFalke commented at 4:45 pm on March 17, 2020:

    in commit d0ebd93270758ea97ea956b8821e17a2d001ea94:

    Actually boost::thread is no longer needed an can be replaced with std::thread in this file and the scheduler tests. I know that the thread group is still boost, but the scheduler doesn’t care about that.

  41. MarcoFalke commented at 4:48 pm on March 17, 2020: member

    ACK 70a6b529f306ff72ea1badf25e970a92b2b17ab3, just style-nits 🌩

    Signature:

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    Timestamp of file with hash 8b7a37edb1d87523e3df70995e0c51ee4dd4dafc50f78c0b12195a66e49c4ce2 -

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ajtowns fanquake DrahtBot elichai MarcoFalke practicalswift jonatack theuni laanwj

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