src: fix platform shutdown deadlock

[Qard]

Fixes #54918

Each worker is signalling its own completion of tasks independently and so should only be signalling for one corresponding drain otherwise the count of outstanding tasks goes out of sync and the process will never stop waiting for tasks when it should be exiting.

It just needs to be calling Signal rather than Broadcast.

Not sure if there was a reason for it to be a broadcast in the first place, but if so then the outstanding_tasks_ count adjustment needs to factor that in properly.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/64837/

[mcollina]

lgtm

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.20%. Comparing base (304bb9c) to head (d674a68).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #56827   +/-   ##
=======================================
  Coverage   89.20%   89.20%           
=======================================
  Files         663      663           
  Lines      192012   192012           
  Branches    36929    36933    +4     
=======================================
+ Hits       171286   171293    +7     
- Misses      13582    13590    +8     
+ Partials     7144     7129   -15     

Files with missing lines	Coverage Δ
src/node_platform.cc	87.83% <100.00%> (ø)

... and 23 files with indirect coverage changes

[targos]

This seems to bring new flakyness to --loader tests, which involve a worker.

[Qard]

I think it may also have not actually fixed the issue, just made it more rare. I've been doing a very long run locally here. Before this I encountered the issue at 9.9k iterations, with this it eventually popped up at 117k iterations.

[lpinca]

Yes, unfortunately it does not seem to fix the issue:

$ python3 tools/test.py --repeat=1000 test/parallel/test-net-write-fully-async-hex-string.js
[00:35|%  98|+ 984|-   0]: release test-net-write-fully-async-hex-string

$ lldb -p 8578
(lldb) process attach --pid 8578
Process 8578 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
    frame #0: 0x00007ff8111b1aaa libsystem_kernel.dylib`__psynch_cvwait + 10
libsystem_kernel.dylib`__psynch_cvwait:
->  0x7ff8111b1aaa <+10>: jae    0x7ff8111b1ab4 ; <+20>
    0x7ff8111b1aac <+12>: movq   %rax, %rdi
    0x7ff8111b1aaf <+15>: jmp    0x7ff8111af662 ; cerror_nocancel
    0x7ff8111b1ab4 <+20>: retq   
Target 0: (node) stopped.
Executable module set to "/Users/luigi/code/node/out/Release/node".
Architecture set to: x86_64-apple-macosx-.
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  * frame #0: 0x00007ff8111b1aaa libsystem_kernel.dylib`__psynch_cvwait + 10
    frame #1: 0x00007ff8111f07a8 libsystem_pthread.dylib`_pthread_cond_wait + 1193
    frame #2: 0x0000000104ffb893 node`uv_cond_wait(cond=<unavailable>, mutex=<unavailable>) at thread.c:819:7 [opt]
    frame #3: 0x00000001041148bb node`node::NodePlatform::DrainTasks(v8::Isolate*) [inlined] node::LibuvMutexTraits::cond_wait(cond=0x00007fdaa3204e78, mutex=0x00007fdaa3204e08) at node_mutex.h:175:5 [opt]
    frame #4: 0x00000001041148a1 node`node::NodePlatform::DrainTasks(v8::Isolate*) [inlined] node::ConditionVariableBase<node::LibuvMutexTraits>::Wait(this=0x00007fdaa3204e78, scoped_lock=<unavailable>) at node_mutex.h:249:3 [opt]
    frame #5: 0x00000001041148a1 node`node::NodePlatform::DrainTasks(v8::Isolate*) [inlined] node::TaskQueue<v8::Task>::BlockingDrain(this=0x00007fdaa3204e08) at node_platform.cc:640:20 [opt]
    frame #6: 0x000000010411488b node`node::NodePlatform::DrainTasks(v8::Isolate*) [inlined] node::WorkerThreadsTaskRunner::BlockingDrain(this=0x00007fdaa3204e08) at node_platform.cc:214:25 [opt]
    frame #7: 0x000000010411488b node`node::NodePlatform::DrainTasks(this=0x0000600002740000, isolate=<unavailable>) at node_platform.cc:467:33 [opt]
    frame #8: 0x0000000103f7ca60 node`node::SpinEventLoopInternal(env=0x00007fdaa5049c00) at embed_helpers.cc:44:17 [opt]
    frame #9: 0x00000001040d9b33 node`node::NodeMainInstance::Run() [inlined] node::NodeMainInstance::Run(this=<unavailable>, exit_code=<unavailable>, env=0x00007fdaa5049c00) at node_main_instance.cc:111:9 [opt]
    frame #10: 0x00000001040d9a99 node`node::NodeMainInstance::Run(this=<unavailable>) at node_main_instance.cc:100:3 [opt]
    frame #11: 0x00000001040414e6 node`node::Start(int, char**) [inlined] node::StartInternal(argc=<unavailable>, argv=<unavailable>) at node.cc:1488:24 [opt]
    frame #12: 0x0000000104041342 node`node::Start(argc=<unavailable>, argv=<unavailable>) at node.cc:1495:27 [opt]
    frame #13: 0x00007ff810e612cd dyld`start + 1805
(lldb)