JDevlieghere added a comment.

In D77295#1996337 <https://reviews.llvm.org/D77295#1996337>, @labath wrote:

> In D77295#1995077 <https://reviews.llvm.org/D77295#1995077>, @JDevlieghere 
> wrote:
>
> > Hi Pavel,
> >
> > After this landed I started seeing a bunch of reproducers fail with 
> > `SIGPIPE`. I ignored the signal and added a check for `EPIPE` to the 
> > `::write` call in `PipePosix.cpp`. Below is the thread state:
> >
> >   * thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGPIPE
> >     * frame #0: 0x00007fff6876c55e libsystem_kernel.dylib`__ulock_wait + 10
> >       frame #1: 0x00007fff6882f5c2 libsystem_pthread.dylib`_pthread_join + 
> > 347
> >       frame #2: 0x000000010115ef62 
> > liblldb.11.0.0git.dylib`lldb_private::HostThreadPosix::Join(this=0x000000011e7ca490,
> >  result=0x00007ffeefbfe290) at HostThreadPosix.cpp:28:15
> >       frame #3: 0x000000010110b64f 
> > liblldb.11.0.0git.dylib`lldb_private::HostThread::Join(this=0x000000011e9f09a0,
> >  result=0x00007ffeefbfe290) at HostThread.cpp:21:27
> >       frame #4: 0x00000001012ea5ba 
> > liblldb.11.0.0git.dylib`lldb_private::Process::ControlPrivateStateThread(this=0x000000011e9f0818,
> >  signal=1) at Process.cpp:3642:30
> >       frame #5: 0x00000001012dbc81 
> > liblldb.11.0.0git.dylib`lldb_private::Process::StopPrivateStateThread(this=0x000000011e9f0818)
> >  at Process.cpp:3593:5
> >       frame #6: 0x00000001012dc514 
> > liblldb.11.0.0git.dylib`lldb_private::Process::Destroy(this=0x000000011e9f0818,
> >  force_kill=true) at Process.cpp:3317:7
> >       frame #7: 0x0000000100981cc1 
> > liblldb.11.0.0git.dylib`lldb::SBProcess::Kill(this=0x000000011e767de0) at 
> > SBProcess.cpp:662:35
> >  
> >   * thread #2
> >     * frame #0: 0x00007fff6876c4ce 
> > libsystem_kernel.dylib`__workq_kernreturn + 10
> >       frame #1: 0x00007fff6882aaa1 
> > libsystem_pthread.dylib`_pthread_wqthread + 390
> >       frame #2: 0x00007fff68829b77 libsystem_pthread.dylib`start_wqthread + 
> > 15
> >  
> >   * thread #3, name = '<lldb.process.internal-state(pid=47347)>'
> >     * frame #0: 0x00007fff6876c55e libsystem_kernel.dylib`__ulock_wait + 10
> >       frame #1: 0x00007fff6882f5c2 libsystem_pthread.dylib`_pthread_join + 
> > 347
> >       frame #2: 0x000000010115ef62 
> > liblldb.11.0.0git.dylib`lldb_private::HostThreadPosix::Join(this=0x000000011e7ca510,
> >  result=0x0000000000000000) at HostThreadPosix.cpp:28:15
> >       frame #3: 0x000000010110b64f 
> > liblldb.11.0.0git.dylib`lldb_private::HostThread::Join(this=0x000000011e9f0e28,
> >  result=0x0000000000000000) at HostThread.cpp:21:27
> >       frame #4: 0x0000000100f46f4e 
> > liblldb.11.0.0git.dylib`lldb_private::Communication::StopReadThread(this=0x000000011e9f0de8,
> >  error_ptr=0x0000000000000000) at Communication.cpp:239:32
> >       frame #5: 0x00000001012e9d95 
> > liblldb.11.0.0git.dylib`lldb_private::Process::ShouldBroadcastEvent(this=0x000000011e9f0818,
> >  event_ptr=0x000000011e76aa40) at Process.cpp:3390:27
> >       frame #6: 0x00000001012e5e4f 
> > liblldb.11.0.0git.dylib`lldb_private::Process::HandlePrivateEvent(this=0x000000011e9f0818,
> >  event_sp=std::__1::shared_ptr<lldb_private::Event>::element_type @ 
> > 0x000000011e76aa40 strong=2 weak=1) at Process.cpp:3697:33
> >       frame #7: 0x00000001012eb147 
> > liblldb.11.0.0git.dylib`lldb_private::Process::RunPrivateStateThread(this=0x000000011e9f0818,
> >  is_secondary_thread=false) at Process.cpp:3891:7
> >       frame #8: 0x00000001012ea2fa 
> > liblldb.11.0.0git.dylib`lldb_private::Process::PrivateStateThread(arg=0x000000011e7c9a60)
> >  at Process.cpp:3789:25
> >       frame #9: 0x000000010110b45b 
> > liblldb.11.0.0git.dylib`lldb_private::HostNativeThreadBase::ThreadCreateTrampoline(arg=0x000000011e7ca4e0)
> >  at HostNativeThreadBase.cpp:68:10
> >       frame #10: 0x000000010726ab83 
> > liblldb.11.0.0git.dylib`lldb_private::HostThreadMacOSX::ThreadCreateTrampoline(arg=0x000000011e7ca4e0)
> >  at HostThreadMacOSX.mm:68:10
> >  
> >   * thread #4, name = '<lldb.comm.process.stdio>', stop reason = breakpoint 
> > 1.1
> >     * frame #0: 0x000000010116071a 
> > liblldb.11.0.0git.dylib`lldb_private::PipePosix::Write(this=0x000000011e7ca2b0,
> >  buf=43698118819080247, size=1, bytes_written=0x00007000076908b8) at 
> > PipePosix.cpp:312:7
> >       frame #1: 0x0000000101156d15 
> > liblldb.11.0.0git.dylib`lldb_private::ConnectionFileDescriptor::Disconnect(this=0x000000011e7ca210,
> >  error_ptr=0x0000000000000000) at ConnectionFileDescriptorPosix.cpp:321:30
> >       frame #2: 0x0000000100f454e6 
> > liblldb.11.0.0git.dylib`lldb_private::Communication::Disconnect(this=0x000000011e9f0de8,
> >  error_ptr=0x0000000000000000) at Communication.cpp:98:46
> >       frame #3: 0x0000000100f46d4e 
> > liblldb.11.0.0git.dylib`lldb_private::Communication::ReadThread(p=0x000000011e9f0de8)
> >  at Communication.cpp:377:13
> >       frame #4: 0x000000010110b45b 
> > liblldb.11.0.0git.dylib`lldb_private::HostNativeThreadBase::ThreadCreateTrampoline(arg=0x000000011e7ca4e0)
> >  at HostNativeThreadBase.cpp:68:10
> >       frame #5: 0x000000010726ab83 
> > liblldb.11.0.0git.dylib`lldb_private::HostThreadMacOSX::ThreadCreateTrampoline(arg=0x000000011e7ca4e0)
> >  at HostThreadMacOSX.mm:68:10
> >       frame #6: 0x00007fff6882e109 libsystem_pthread.dylib`_pthread_start + 
> > 148
> >       frame #7: 0x00007fff68829b8b libsystem_pthread.dylib`thread_start + 15
> >
> >
> > Any chance you might know what's going on here?
>
>
> Hm... this probably didn't introduce the bug, but I can certainly see how it 
> could cause an existing issue to start to appear more often.
>
> I think I have an idea for what could be problem here -- a race between the 
> Disconnect call in `Communication::ReadThread` and the one in 
> `Process::ShouldBroadcastEvent`. Can you check if swapping the order of these 
> two lines in `Process::ShouldBroadcastEvent`:
>
>   m_stdio_communication.Disconnect();
>   m_stdio_communication.StopReadThread();
>   
>
> makes the problem go away?


Thanks, that did the trick! (b424b0bf731d1fb338180553a86f912746f640ad 
<https://reviews.llvm.org/rGb424b0bf731d1fb338180553a86f912746f640ad>)


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D77295/new/

https://reviews.llvm.org/D77295



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