1. 04 Nov, 2019 5 commits
  2. 31 Oct, 2019 1 commit
    • Kirill Smelkov's avatar
      libgolang: Fix build with old gcc · 77719d8a
      Kirill Smelkov authored
      Gcc 5.4 from Ubuntu 16.04 LTS complains e.g.
      
          ./golang/libgolang.h: In function ‘golang::_selcase golang::_selrecv_(golang::_chan*, void*, bool*)’:
          ./golang/libgolang.h:227:5: sorry, unimplemented: non-trivial designated initializers not supported
               };
               ^
      
      The problem started to appear after 47111d3e (libgolang: Teach select to accept
      inplace tx data) when we moved _selcase.ptxrx inside union.
      
      Let's add workaround for older compilers, even though e.g. gcc 8.3 from Debian
      10 accepts existing code just fine.
      77719d8a
  3. 30 Oct, 2019 1 commit
    • Kirill Smelkov's avatar
      sync: Move/Port WaitGroup to C++/Pyx nogil · b316e504
      Kirill Smelkov authored
      Provide sync.WaitGroup that can be used directly from C++ and Pyx/nogil codes.
      Python-level sync.WaitGroup becomes small wrapper around pyx/nogil one.
      
      Python-level tests should be enough to cover C++/Pyx functionality at
      zero-level approximation.
      b316e504
  4. 24 Oct, 2019 1 commit
  5. 22 Oct, 2019 1 commit
    • Kirill Smelkov's avatar
      libgolang: Expose defer as public C++ API · 1d153a45
      Kirill Smelkov authored
      Libgolang, since 3b241983 (Port/move channels to C/C++/Pyx), already had
      defer macro implemented and used, but only internally. The reason it was
      not yet exposed as public API is that there is a difference with Go's
      defer in that deferred function is called at end of current scope
      instead of end of current function, and I was a bit reluctant to expose
      defer with different-than-Go semantic.
      
      However even with this difference defer is useful, and the difference
      can be documented. Unfortunately it is not easy to correctly fix the
      difference, so the most practical way for now is to expose defer as it is.
      
      I've also contemplated how to avoid using macro, but without a macro,
      users will have to explicitly declare placeholder variable for every
      defer call which goes against usability.
      
      Since defer is exposed as macro, I've also contemplated to expose it as
      something like `libgolang_defer` with the idea to avoid name conflicts,
      and so that users - that are using defer - will be doing `#define defer
      libgolang_defer`. However I ended up not doing that and exposing `defer`
      macro with its own name. My rationale is:
      
      - grepping /usr/include/ for \<defer\> on my system did not showed any
        real usage.
      - Qt also #defines `slots` and `signals` and that does not cause
        problems in practice.
      
      -> expose `defer` macro into public C++ API as is, so that it can be
      used not only inside libgolang.cpp . For example I myself need defer
      functionality in C++ part of wendelin.core.
      1d153a45
  6. 18 Oct, 2019 3 commits
    • Kirill Smelkov's avatar
      golang: Fix recover to clear current exception · 9e6ff8bd
      Kirill Smelkov authored
      Else the exception, even if it was recovered from, will be included as
      cause for next raised exception. See added test for details.
      9e6ff8bd
    • Kirill Smelkov's avatar
      golang: Teach defer to chain exceptions (PEP 3134) even on Python2 · bb9a94c3
      Kirill Smelkov authored
      Python3 chains exceptions, so that e.g. if exc1 is raised and, while it
      was not handled, another exc2 is raised, exc2 will be linked to exc1 via
      exc2.__context__ attribute and exc1 will be included into exc2 traceback
      printout. However many projects still use Python2 and there is no
      similar chaining functionality there. This way exc1 is completely lost.
      
      Since defer code is in our hands, we can teach it to implement exception
      chaining even on Python2 by carefully analyzing what happens in
      _GoFrame.__exit__().
      
      Implementing chaining itself is relatively easy, but is only part of the
      story. Even if an exception is chained with its cause, but exception
      dump does not show the cause, the chaining will be practically useless.
      With this in mind this patches settles not only on implementing chaining
      itself, but on also giving a promise that chained cause exceptions will
      be included into traceback dumps as well.
      
      To realize this promise we adjust all exception dumping funcitons in
      traceback module and carefully install adjusted
      traceback.print_exception() into sys.excepthook. This amends python
      interactive sessions and programs run by python interpreter to include
      causes in exception dumps. "Careful" here means that we don't change
      sys.excepthook if on golang module load we see that sys.excepthook was already
      changed by some other module - e.g. due to IPython session running
      because IPython installs its own sys.excepthook. In such cases we don't
      install our sys.excepthook, but we also provide integration patches that
      add exception chaining support for traceback dump functionality in
      popular third-party software. The patches (currently for IPython and
      Pytest) are activated automatically, but only when/if corresponding
      software is imported and actually used. This should give practically
      good implementation of the promise - a user can now rely on seeing
      exception cause in traceback dump whatever way python programs are run.
      
      The implementation takes https://pypi.org/project/pep3134/ experience
      into account [1]. peak.utils.imports [2,3] is used to be notified when/if
      third-party module is imported.
      
      [1] https://github.com/9seconds/pep3134/
      [2] https://pypi.org/project/Importing/
      [3] http://peak.telecommunity.com/DevCenter/Importing
      
      This patch originally started as hacky workaround in wendelin.core
      because in wcfs tests I was frequently hitting situations, where
      exception raised by an assert was hidden by another exception raised in
      further generic teardown check. For example wcfs tests check that wcfs
      is unmounted after every test run [4] and if that fails it was hiding
      problems raised by an assert. As the result I was constantly guessing
      and adding code like [5] to find what was actually breaking. At some
      point I added hacky workaround for defer to print cause exception not to
      loose it [6]. [7] has more context and background discussion on this topic.
      
      [4] https://lab.nexedi.com/kirr/wendelin.core/blob/49e73a6d/wcfs/wcfs_test.py#L70
      [5] https://lab.nexedi.com/kirr/wendelin.core/blob/49e73a6d/wcfs/wcfs_test.py#L853-857
      [6] kirr/wendelin.core@c00d94c7
      [7] zodbtools!13 (comment 81553)
      
      After this patch, on Python2
      
          defer(cleanup1)
          defer(cleanup2)
          defer(cleanup3)
          ...
      
      is no longer just a syntatic sugar for
      
          try:
              try:
                  try:
                      ...
                  finally:
                      cleanup3()
              finally:
                  cleanup2()
          finally:
              cleanup1()
      bb9a94c3
    • Kirill Smelkov's avatar
      golang_test: Split pyrun into -> _pyrun & pyrun · 6729fe92
      Kirill Smelkov authored
      - _pyrun runs the command and returns full information: exitcode, stdout, stderr.
      - pyrun  runs the command and raises exception if ran command fails.
      
      We will need _pyrun in the next patch to test that particular command
      fails and access its stderr.
      6729fe92
  7. 15 Oct, 2019 2 commits
  8. 14 Oct, 2019 9 commits
    • Kirill Smelkov's avatar
      time: Switch internals to pyx/nogil · 8c2ac5e9
      Kirill Smelkov authored
      - use .c.chan_double() which gives chan[double] pyx/nogil way to access
        Ticker.c and Timer.c. Use the channels via pyx/nogil API from inside.
      - use pyx/nogil sleep and now;
      
      This gets time.pyx codebase closer to be used from pyx/nogil mode.
      
      NOTE: unless something like pyx/nogil memory management emerges[1] we
      are relying on Python to manage memory of Ticker and Timer classes.
      If we just spawn e.g. Ticker.__tick via pyx/nogil go, the thread that is
      spawned won't be holding a reference to Ticker object, and once the
      ticker goes out of scope in original thread (while its channel .c might
      be still in scope), __tick will segfault accessing freed Ticker object.
      
      To workaround it we use the following pattern:
      
          nogilready = chan(dtype='C.structZ')
          pygo(mymeth)
          nogilready.recv()
      
          def mymeth(MyObject self, pychan nogilready)
              with nogil:
                  nogilready.chan_structZ().close()
                  self._mymeth()
          cdef void _mymeth(MyObject self) nogil:
              ...
      
      where python reference to MyObject will be held in spawned thread during
      its lifetime, while the service provided by mymeth will be done under
      nogil.
      
      [1] https://www.nexedi.com/blog/NXD-Document.Blog.Cypclass
      8c2ac5e9
    • Kirill Smelkov's avatar
      time: Switch Timer/Ticker channels from chan() -> chan(dtype='C.double') · 7c929b25
      Kirill Smelkov authored
      This will allow to use the channels in nogil mode including in followup
      patches touching time.pyx codebase.
      7c929b25
    • Kirill Smelkov's avatar
      context: Switch done channel from chan() to -> chan(dtype='C.structZ') · 149ae661
      Kirill Smelkov authored
      C.structZ is empty structure and chan[C.structZ] can be used in
      pyx/nogil world. This way context tree initially created from Python can
      be extended in pyx/nogil and e.g. root context can be canceled from
      Python, which will correctly transfer the cancelation signal to pyx/nogil
      world too.
      149ae661
    • Kirill Smelkov's avatar
      golang: Teach pychan to work with channels of C types, not only PyObjects · 3121b290
      Kirill Smelkov authored
      Introduce notion of data type (dtype similarly to NumPy) into pychan and
      teach it to accept for send objects only matching that dtype. Likewise
      teach pychan to decode raw bytes received from underlying channel into
      Python object correspodningg to pychan dtype. For C dtypes, e.g.
      'C.int', 'C.double' etc, contrary to chan of python objects, the
      transfer can be done without depending on Python GIL. This way channels
      of such C-level dtypes can be used to implement interaction in between
      Python and nogil worlds.
      3121b290
    • Kirill Smelkov's avatar
      *: Channels must be compared by ==, not by "is" even for nilchan · 2c8063f4
      Kirill Smelkov authored
      In a followup commit we are going to add channel types (e.g. chan of
      double, chan of int, etc) and accordingly there will be several nil
      channel objects, e.g. nil(dtype=int), nil(dtype=double) etc, which will
      be separate python objects. Even without data types, another planned
      change is to add directional channels, e.g. a channel instance that can
      only send, but not receive and vice versa(*).
      
      This way for the same underlying channel object, there can be several
      pychan objects that point to it - even for nil channel - e.g. nilchan
      and `niltx = nilchan.txonly()` that creates another pychan object
      pointing to the same underlying nil.
      
      Since we want all channels (of the same type) that point to the same
      underlying channel to compare as same, we cannot use "is" for comparison
      and have to use ==. In other words channels, both at C and Python level,
      should be perceived as pointers, of which there can be multiple ones
      pointing to the same location, and thus == has to be used to compare
      them.
      
      (*) see https://golang.org/ref/spec#Channel_types for details.
      2c8063f4
    • Kirill Smelkov's avatar
      *: Annotate method receiver with corresponding type for all cdef classes · f6fab7b5
      Kirill Smelkov authored
      For example
      
          -    def send(pych, obj):
          +    def send(pychan pych, obj):
      
      Even though Cython allows not to annotate self with type, this makes the
      code more clear.
      f6fab7b5
    • Kirill Smelkov's avatar
      golang: pyselect: Switch into using inplace tx data · 30561db4
      Kirill Smelkov authored
      This prepares pyselect codebase for future logic where all channel
      element types will be sent via inplace _selcase data. For PyObject we
      could previously go with "wiring ptx through pycase[1]", but for
      arbitrary type, that has to be first converted from Python object to
      C-level object, we would have to store the result somewhere, and that
      would mean extra allocation and pyselect code complexity increase, even
      for cases that don't use anything but chan[object].
      
      So do the preparation and switch pyselect into using inplace tx.
      30561db4
    • Kirill Smelkov's avatar
      libgolang: Teach select to accept inplace tx data · 47111d3e
      Kirill Smelkov authored
      Currently select, via _selcase, requires users to provide pointers to tx
      and rx buffers. However if element type itself can fit into a pointer
      word, we can put the element directly into _selcase and mark the case
      with a flag, that it contains inplace data instead of referring to
      external storage. This will be helpful in upcoming patch where we'll
      teach pychan to work with several element types, not only pyobject
      elements.
      
      This patch does careful introduction of _selcase.flags - in such a way
      that the size of _selcase stays the same as it was before by using
      bitfields. The .ptxrx pointer is unioned with newly introduced inplace
      uint64 .itxrx data, which is used by select instead of .ptxrx if the
      flag is set. The usage of uint64 should not increase _selcase size on
      64-bit platforms.
      
      Then _selcase.ptx() and .prx() accessors are adapted accordingly and
      the rest of the changes are corresponding test and
      _chanselect2<onstack=false> adaptation.
      
      This functionality is kind of low-level and is not exposed via any
      _selsend() or chan.sends() API changes. Whenever inplace tx should be
      used, the case should be prepared either completely manually, or with
      e.g. first calling _selsend() and then manually changing .flags and
      .itxrx.  Added test serves as the example on how to do it.
      
      Inplace rx is currently forbidden - because supporting that would require
      to drop const from casev select argument. However in the future, for
      symmetry, we might want to support that as well.
      
      P.S.
      
      Since write to selcase.itxrx requires casting pointers e.g. like this:
      
      	*(int *)&sel[0].itxrx = 12345;
      
      it breaks C99 strict aliasing and by default compiler can generate bad
      code on such pattern. To the problem we adapt the build system
      to default compiler to no-strict-aliasing (as many other projects do,
      e.g. Linux kernel) with the idea that in many cases where strict
      aliasing was intended to help it actually does not, because e.g. pointer
      types are the same, while explicitly marking pointers with `restrict`
      keyword does help indeed.
      
      Nothing new for Python2 here, as it is using -fno-strict-aliasing by
      itself. However Python3 is compiling without -fno-strict-aliasing:
      https://python.org/dev/peps/pep-3123 .
      47111d3e
    • Kirill Smelkov's avatar
      libgolang: _selcase: Introduce accessors to get pointers to for-send and for-recv data · 2590e9a7
      Kirill Smelkov authored
      In the next patch we are going to teach _selcase to support both
      external and inplace data. Before that let's do a couple of preparatory
      things.
      
      This patch: introduces .ptx() and .prx() accessors to get to
      corresponding data buffer associated with _selcase. Convert _selcase
      users to use .ptx() and .prx() instead of doing direct .ptxrx access.
      This way when we'll add inplace support to _selcase, we'll need to adapt
      only accessors, not clients.
      
      The only place that is left using .ptxrx directly is one tricky place in
      _chanselect2<onstack=false> where gevent-related code needs to carefully
      deal with proxying tx/rx buffers due to STACK_DEAD_WHILE_PARKED.
      
      NOTE even though new accessors may panic, libgolang.cpp always calls them
      after checking that the conditions for ptx/prx calls are valid.
      2590e9a7
  9. 13 Oct, 2019 3 commits
    • Kirill Smelkov's avatar
      libgolang: _selcase: Rename .data -> .ptxrx · d6c8862d
      Kirill Smelkov authored
      In the next patches we are going to teach _selcase to support both
      external and inplace data. Before that let's do a couple of preparatory
      things.
      
      This patch: rename .data -> .ptxrx . The new name is more clear:
      
      - "p" prefix aligns with other libgolang style, e.g. ptx or prx.
      - "txrx" suffix says that this is used for both send and recv.
      
      Just plain renaming, nothing else in this patch.
      d6c8862d
    • Kirill Smelkov's avatar
      golang: pyselect: Fix tx object reference leak on error exit · e9180de1
      Kirill Smelkov authored
      Before passing objects to _chanselect for send, pyselect increfs them, as just
      send does, to indicate that one object reference is passed to channel buffer.
      On exit, since only one case is actually executed by select, pyselect needs to
      decref incref'ed object from not executed cases.
      
      Pyselect already implements the latter cleanup, but currently the cleanup is
      executed only if control flow reaches _chanselect at all. Which is a bug, since
      pyselect can panic or raise an exception just in the middle of preparation phase.
      
      -> Fix it by associating the finally-decref cleanup with whole
      prepare+_chanselect code.
      
      Without the fix, the second part of added test (abnormal exit) fails e.g. like:
      
              @mark.skipif(not hasattr(sys, 'getrefcount'),   # skipped e.g. on PyPy
                           reason="needs sys.getrefcount")
              def test_select_refleak():
                  ch1 = chan()
                  ch2 = chan()
                  obj1 = object()
                  obj2 = object()
                  tx1 = (ch1.send, obj1)
                  tx2 = (ch2.send, obj2)
      
                  # normal exit
                  gc.collect()
                  nref1 = sys.getrefcount(obj1)
                  nref2 = sys.getrefcount(obj2)
                  _, _rx = select(
                      tx1,        # 0
                      tx2,        # 1
                      default,    # 2
                  )
                  assert (_, _rx) == (2, None)
                  gc.collect()
                  assert sys.getrefcount(obj1) == nref1
                  gc.collect()
                  assert sys.getrefcount(obj1) == nref2
      
                  # abnormal exit
                  with raises(AttributeError) as exc:
                      select(
                          tx1,        # 0
                          tx2,        # 1
                          'zzz',      # 2 causes pyselect to panic
                      )
                  assert exc.value.args == ("'str' object has no attribute '__self__'",)
                  gc.collect()
          >       assert sys.getrefcount(obj1) == nref1
          E       assert 4 == 3
          E         -4
          E         +3
      
          golang/golang_test.py:690: AssertionError
      
      The bug was introduced in 3b241983 (Port/move channels to C/C++/Pyx).
      e9180de1
    • Kirill Smelkov's avatar
      golang: Rework pychan to use C-level channel API · f2847307
      Kirill Smelkov authored
      We will soon rework pychan to be python wrapper not only for
      chan<object>, but also for other channels of various C types - e.g.
      chan<structZ>, chan<int>, etc.
      
      To prepare for this let's first rework pychan from using chan[PyObject*]
      into raw _chan* functions. This will allow us to use the same functions
      over raw channels while dynamically dispatching on channel element type.
      f2847307
  10. 05 Oct, 2019 3 commits
  11. 04 Oct, 2019 4 commits
    • Kirill Smelkov's avatar
      time: Move code to pyx · 32f34607
      Kirill Smelkov authored
      In preparation to start migrating, at least partly, time functionality
      to nogil mode, move the code from time.py to _time.pyx . This is straight
      code movement except
      
      	now	-> pynow, and
      	sleep	-> pysleep
      
      replaces, since in _time.pyx now and sleep were already referring to
      nogil versions.
      
      We don't move just to time.pyx (note no _ prefix), since we will need to
      continue distinguishing pyx/nogil from py objects/functions, e.g.
      pyx time.second is C constant, while pyx time.pysecond is pyobject
      exported to python world as time.second.
      32f34607
    • Kirill Smelkov's avatar
      *: Add missing __future__ imports · bfbdc711
      Kirill Smelkov authored
      One place in _time.pyx was overlooked in ce8152a2 (pyx api: Provide sleep).
      bfbdc711
    • Kirill Smelkov's avatar
      *: threading.Lock -> sync.Mutex · 548f2df1
      Kirill Smelkov authored
      Similarly to 78d85cdc (sync: threading.Event -> chan) replace everywhere
      threaing.Lock usage with sync.Mutex . This brings 2 goods:
      
      - sync.Mutex becomes more well tested;
      - we untie ourselves from threading python module (threading.Lock was
        the last user).
      548f2df1
    • Kirill Smelkov's avatar
      golang: Expose Sema and Mutex as public Python and Cython/nogil API · 34b7a1f4
      Kirill Smelkov authored
      Until now libgolang had semaphore and mutex functionality, but
      implemented only internally and not exposed to users. Since for its
      pinner thread wendelin.core v2 needs not only nogil channels, but also
      nogil mutexes, timers and so on, it is now time to start providing that.
      
      We start with mutexes:
      
      - Expose Mutex from insides of libgolang.cpp to public API in
        libgolang.h . We actually expose both Mutex and Sema because
        semaphores are sometimes also useful for low-level synchronization,
        and because it is easier to export Mutex and Sema both at the same time.
      
      - Provide pyx/nogil API to those as sync.Mutex and sync.Sema.
      
      - Provide corresponding python wrappers.
      
      - Add Pyx-level test for semaphore wakeup when wakeup is done not by the
        same thread which did the original acquire. This is the test that was
        promised in 5142460d (libgolang/thread: Add links to upstream
        PyThread_release_lock bug), and it used to corrupt memory and deadlock
        on macOS due to CPython & PyPy runtime bugs:
      
          https://bugs.python.org/issue38106
            -> https://github.com/python/cpython/pull/16047
          https://bitbucket.org/pypy/pypy/issues/3072
      
      Note about python wrappers: At present, due to
      https://github.com/cython/cython/issues/3165, C-level panic is not
      properly translated into Py-level exception in (Py)Sema/Mutex constructors.
      This should not pose a real problem in practice though.
      34b7a1f4
  12. 03 Oct, 2019 4 commits
    • Kirill Smelkov's avatar
      libgolang: Small cosmetics · f0ac6e45
      Kirill Smelkov authored
      - Fix references to time::sleep and _tasknanosleep in library overview.
      - add golang::time:: comment before openeing corresponding namespace.
      f0ac6e45
    • Kirill Smelkov's avatar
      golang: tests: Factor out code to import test from a pyx module into import_pyx_test · 9c795ca7
      Kirill Smelkov authored
      We will soon need this functionality for sync_test.py to import tests
      from _sync_test.pyx . In the future many modules will need to import
      X_test.pyx from X_test.py as well.
      9c795ca7
    • Kirill Smelkov's avatar
      libgolang: Switch _makechan to panic instead of return NULL on failure · d99bb6b7
      Kirill Smelkov authored
      - it is in Go style to panic on memory allocation failure.
      - _makechan can already panic, instead of returning NULL, on e.g. ch._mu
        initialization failure.
      - we were already not checking in several places for NULL after
        _makechan() call (e.g. in golang/runtime/libgolang_test_c.c).
      
      This switches _makechan to panic on memory allocation failure and
      settles on style of future C-level API calls to panic instead of
      returning NULL on failure.
      d99bb6b7
    • Kirill Smelkov's avatar
      gpython: Kill stray `import sys` · c489bd5f
      Kirill Smelkov authored
      sys is imported in the beginning of main, so there is no need to import
      it the second time in the middle of main. The bug was there since
      gpython day1 - since 32a21d5b (gpython: Python interpreter with support
      for lightweight threads).
      c489bd5f
  13. 17 Sep, 2019 3 commits
    • Kirill Smelkov's avatar
      pygolang v0.0.4 · 1573d101
      Kirill Smelkov authored
      This release is bugfix-only. Compared to pygolang v0.0.3 (4ca65816)
      the change in speed is likely within noise:
      
           (on i7@2.6GHz)
      
      thread runtime:
      
          name             old time/op  new time/op  delta
          go               18.3µs ± 1%  18.3µs ± 1%    ~     (p=0.218 n=10+10)
          chan             2.97µs ± 5%  2.97µs ± 8%    ~     (p=0.781 n=10+10)
          select           3.59µs ± 2%  3.55µs ± 5%    ~     (p=0.447 n=9+10)
          def              56.0ns ± 0%  55.0ns ± 0%  -1.79%  (p=0.000 n=10+10)
          func_def         43.7µs ± 1%  43.8µs ± 1%  +0.35%  (p=0.029 n=10+10)
          call             65.0ns ± 0%  62.3ns ± 1%  -4.15%  (p=0.000 n=10+10)
          func_call        1.06µs ± 1%  1.04µs ± 0%  -1.26%  (p=0.000 n=10+8)
          try_finally       137ns ± 1%   137ns ± 0%    ~     (p=1.000 n=10+10)
          defer            2.32µs ± 0%  2.33µs ± 1%  +0.43%  (p=0.000 n=9+10)
          workgroup_empty  37.6µs ± 1%  37.1µs ± 2%  -1.29%  (p=0.003 n=10+10)
          workgroup_raise  47.9µs ± 1%  47.6µs ± 0%  -0.63%  (p=0.001 n=9+9)
      
      gevent runtime:
      
          name             old time/op  new time/op  delta
          go               15.8µs ± 0%  16.1µs ± 1%  +2.18%  (p=0.000 n=9+10)
          chan             7.36µs ± 0%  7.21µs ± 0%  -1.97%  (p=0.000 n=8+10)
          select           10.4µs ± 0%  10.5µs ± 0%  +0.71%  (p=0.000 n=10+10)
          def              57.0ns ± 0%  55.0ns ± 0%  -3.51%  (p=0.000 n=10+10)
          func_def         43.3µs ± 1%  44.1µs ± 2%  +1.81%  (p=0.000 n=10+10)
          call             66.0ns ± 0%  65.0ns ± 0%  -1.52%  (p=0.000 n=10+10)
          func_call        1.04µs ± 1%  1.06µs ± 1%  +1.48%  (p=0.000 n=10+10)
          try_finally       137ns ± 1%   136ns ± 0%  -1.31%  (p=0.000 n=10+10)
          defer            2.32µs ± 0%  2.31µs ± 1%    ~     (p=0.472 n=8+10)
          workgroup_empty  56.0µs ± 0%  55.7µs ± 0%  -0.49%  (p=0.000 n=10+10)
          workgroup_raise  71.3µs ± 1%  71.7µs ± 1%  +0.62%  (p=0.001 n=10+10)
      1573d101
    • Kirill Smelkov's avatar
      libgolang: select: zero-out waitv before freeing · 2e01f9bd
      Kirill Smelkov authored
      Like we already do for e.g. _chan, to increase probability that if
      something is used after free we get a NULL-dereference crash instead of
      more hard-to-understand segfault.
      2e01f9bd
    • Kirill Smelkov's avatar
      libgolang: Fix select crash while accessing destroyed channel upon wakeup · 5aa1e899
      Kirill Smelkov authored
      Similarly to situation described in dcf4ebd1 (libgolang: Fix chan.close
      to dequeue subscribers atomically), select can be also accessing a
      channel object at the time of wakeup when that channel could be already
      destroyed: select queues waiters to channels recv/send queues and upon
      wakeup needs to dequeue them. This requires locking channels, not to
      mention that a channel destroy with non-empty subscribers queue will
      trigger bug panic.
      
      Contrary to the fix for recv, we cannot rework select not to access
      channel objects after wakeup, because for select upon wakeup all queued
      channels could be already destroyed, not only selected one. Thus the fix
      here is to incref/decref the channels for the duration where we need to
      access them.
      
      The bug was not caught by existing tests and was noted while doing
      libgolang.cpp review for concurrency issues. With added test (hereby fix
      is served by a bit amended _test_close_wakeup_all) the bug, if not
      fixed, renders itself as e.g. the following under TSAN:
      
      WARNING: ThreadSanitizer: data race (pid=4421)
        Write of size 8 at 0x7b1400000650 by thread T9:
          #0 free ../../../../src/libsanitizer/tsan/tsan_interceptors.cc:649 (libtsan.so.0+0x2b46a)
          #1 free ../../../../src/libsanitizer/tsan/tsan_interceptors.cc:643 (libtsan.so.0+0x2b46a)
          #2 golang::_chan::decref() golang/runtime/libgolang.cpp:479 (liblibgolang.so.0.1+0x4822)
          #3 _chanxdecref golang/runtime/libgolang.cpp:461 (liblibgolang.so.0.1+0x487a)
          #4 golang::chan<int>::operator=(decltype(nullptr)) golang/libgolang.h:296 (_golang_test.so+0x14cf9)
          #5 operator() golang/runtime/libgolang_test.cpp:304 (_golang_test.so+0x14cf9)
          #6 __invoke_impl<void, __test_close_wakeup_all(bool)::<lambda()>&> /usr/include/c++/8/bits/invoke.h:60 (_golang_test.so+0x14cf9)
          #7 __invoke<__test_close_wakeup_all(bool)::<lambda()>&> /usr/include/c++/8/bits/invoke.h:95 (_golang_test.so+0x14cf9)
          #8 __call<void> /usr/include/c++/8/functional:400 (_golang_test.so+0x14cf9)
          #9 operator()<> /usr/include/c++/8/functional:484 (_golang_test.so+0x14cf9)
          #10 _M_invoke /usr/include/c++/8/bits/std_function.h:297 (_golang_test.so+0x14cf9)
          #11 std::function<void ()>::operator()() const /usr/include/c++/8/bits/std_function.h:687 (_golang_test.so+0x1850c)
          #12 operator() golang/libgolang.h:273 (_golang_test.so+0x1843a)
          #13 _FUN golang/libgolang.h:271 (_golang_test.so+0x1843a)
          #14 <null> <null> (python2.7+0x1929e3)
      
        Previous read of size 8 at 0x7b1400000650 by thread T10:
          #0 golang::Sema::acquire() golang/runtime/libgolang.cpp:168 (liblibgolang.so.0.1+0x413a)
          #1 golang::Mutex::lock() golang/runtime/libgolang.cpp:179 (liblibgolang.so.0.1+0x424a)
          #2 operator() golang/runtime/libgolang.cpp:1044 (liblibgolang.so.0.1+0x424a)
          #3 _M_invoke /usr/include/c++/8/bits/std_function.h:297 (liblibgolang.so.0.1+0x424a)
          #4 std::function<void ()>::operator()() const /usr/include/c++/8/bits/std_function.h:687 (liblibgolang.so.0.1+0x5f07)
          #5 golang::_deferred::~_deferred() golang/runtime/libgolang.cpp:215 (liblibgolang.so.0.1+0x5f07)
          #6 __chanselect2 golang/runtime/libgolang.cpp:1044 (liblibgolang.so.0.1+0x5f07)
          #7 _chanselect2<true> golang/runtime/libgolang.cpp:968 (liblibgolang.so.0.1+0x6665)
          #8 _chanselect golang/runtime/libgolang.cpp:963 (liblibgolang.so.0.1+0x6665)
          #9 select golang/libgolang.h:386 (_golang_test.so+0x14fc1)
          #10 operator() golang/runtime/libgolang_test.cpp:320 (_golang_test.so+0x14fc1)
          #11 __invoke_impl<void, __test_close_wakeup_all(bool)::<lambda()>&> /usr/include/c++/8/bits/invoke.h:60 (_golang_test.so+0x14fc1)
          #12 __invoke<__test_close_wakeup_all(bool)::<lambda()>&> /usr/include/c++/8/bits/invoke.h:95 (_golang_test.so+0x14fc1)
          #13 __call<void> /usr/include/c++/8/functional:400 (_golang_test.so+0x14fc1)
          #14 operator()<> /usr/include/c++/8/functional:484 (_golang_test.so+0x14fc1)
          #15 _M_invoke /usr/include/c++/8/bits/std_function.h:297 (_golang_test.so+0x14fc1)
          #16 std::function<void ()>::operator()() const /usr/include/c++/8/bits/std_function.h:687 (_golang_test.so+0x1850c)
          #17 operator() golang/libgolang.h:273 (_golang_test.so+0x183da)
          #18 _FUN golang/libgolang.h:271 (_golang_test.so+0x183da)
          #19 <null> <null> (python2.7+0x1929e3)
      
        Thread T9 (tid=4661, running) created by main thread at:
          #0 pthread_create ../../../../src/libsanitizer/tsan/tsan_interceptors.cc:915 (libtsan.so.0+0x2be1b)
          #1 PyThread_start_new_thread <null> (python2.7+0x19299f)
          #2 _taskgo golang/runtime/libgolang.cpp:123 (liblibgolang.so.0.1+0x3f98)
          #3 go<__test_close_wakeup_all(bool)::<lambda()> > golang/libgolang.h:271 (_golang_test.so+0x16c94)
          #4 __test_close_wakeup_all(bool) golang/runtime/libgolang_test.cpp:298 (_golang_test.so+0x16c94)
          #5 _test_close_wakeup_all_vsselect() golang/runtime/libgolang_test.cpp:342 (_golang_test.so+0x16f64)
          #6 __pyx_pf_6golang_12_golang_test_24test_close_wakeup_all_vsselect golang/_golang_test.cpp:4013 (_golang_test.so+0xd92a)
          #7 __pyx_pw_6golang_12_golang_test_25test_close_wakeup_all_vsselect golang/_golang_test.cpp:3978 (_golang_test.so+0xd92a)
          #8 PyEval_EvalFrameEx <null> (python2.7+0xf68b4)
      
        Thread T10 (tid=4662, running) created by main thread at:
          #0 pthread_create ../../../../src/libsanitizer/tsan/tsan_interceptors.cc:915 (libtsan.so.0+0x2be1b)
          #1 PyThread_start_new_thread <null> (python2.7+0x19299f)
          #2 _taskgo golang/runtime/libgolang.cpp:123 (liblibgolang.so.0.1+0x3f98)
          #3 go<__test_close_wakeup_all(bool)::<lambda()> > golang/libgolang.h:271 (_golang_test.so+0x16d96)
          #4 __test_close_wakeup_all(bool) golang/runtime/libgolang_test.cpp:315 (_golang_test.so+0x16d96)
          #5 _test_close_wakeup_all_vsselect() golang/runtime/libgolang_test.cpp:342 (_golang_test.so+0x16f64)
          #6 __pyx_pf_6golang_12_golang_test_24test_close_wakeup_all_vsselect golang/_golang_test.cpp:4013 (_golang_test.so+0xd92a)
          #7 __pyx_pw_6golang_12_golang_test_25test_close_wakeup_all_vsselect golang/_golang_test.cpp:3978 (_golang_test.so+0xd92a)
          #8 PyEval_EvalFrameEx <null> (python2.7+0xf68b4)
      
      and reliably crashes under regular builds.
      5aa1e899