llunak marked 2 inline comments as done.
llunak added inline comments.
================
Comment at: lldb/source/Core/Debugger.cpp:1969
+llvm::ThreadPool &Debugger::GetThreadPool() {
+ static llvm::ThreadPool threadpool(llvm::optimal_concurrency());
+ return threadpool;
----------------
clayborg wrote:
> clayborg wrote:
> > llunak wrote:
> > > clayborg wrote:
> > > > aganea wrote:
> > > > > clayborg wrote:
> > > > > > aganea wrote:
> > > > > > > Ideally this should be explicitly created on the stack & passed
> > > > > > > along on the callstack or in a context, like MLIR does:
> > > > > > > https://github.com/llvm/llvm-project/blob/main/mlir/include/mlir/IR/MLIRContext.h#L48
> > > > > > We need one instance of the thread pool so we can't create on the
> > > > > > stack.
> > > > > >
> > > > > > Static is not great because of the C++ global destructor chain
> > > > > > could try and use if "main" exits and we still have threads
> > > > > > running. I would do something like the "g_debugger_list_ptr" where
> > > > > > you create a static variable in Debugger.cpp:105 which is a
> > > > > > pointer, and we initialize it inside of Debugger::Initialize() like
> > > > > > we do for "g_debugger_list_ptr". Then the thread pool will not
> > > > > > cause shutdown crashes when "main" exits before other threads.
> > > > > >
> > > > > I meant having the `ThreadPool` in a context created by main() or the
> > > > > lib caller, before getting here in library/plugin code, and passed
> > > > > along. LLD does that too:
> > > > > https://github.com/llvm/llvm-project/blob/main/lld/ELF/Driver.cpp#L94
> > > > > - the statics in `Debugger.cpp` seems like a workaround for that. In
> > > > > any case, it's better than having the `static` here.
> > > > In LLDB, the lldb_private::Debugger has static functions that hand out
> > > > things that are needed for the debugger to do its work, so I like the
> > > > static function here. We don't allow any llvm or clang code to make it
> > > > through our public API (in lldb::SB* classes), so we do need code
> > > > inside the debugger to be able to access global resources and the
> > > > debugger class is where this should live.
> > > >
> > > > We can also just have code like:
> > > > ```
> > > > // NOTE: intentional leak to avoid issues with C++ destructor chain
> > > > static llvm::ThreadPool *g_thread_pool = nullptr;
> > > > static llvm::once_flag g_once_flag;
> > > > llvm::call_once(g_once_flag, []() {
> > > > g_thread_pool = new llvm::ThreadPool(llvm::optimal_concurrency());
> > > > });
> > > > return *g_thread_pool;
> > > > ```
> > > >
> > > I've changed the code to initialize/cleanup from Debugger ctor/dtor.
> > >
> > You can't do this as there can be more than one debugger. This needs to be
> > a true global and use a once_flag.
> >
> > Xcode creates one debugger per target window, that way each one has its own
> > command interpreter etc;
> Probably best to do it as described above where everything is contained in
> this function due to multiple debuggers being possible, so we can't tie
> anything to the lifetime of any debugger and we need to not crash when the
> main thread exits first
I see, I thought there could be just one Debugger instance. I'll use the
call_once code from above then.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D123226/new/
https://reviews.llvm.org/D123226
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