https://github.com/mono/mono/pull/5599 fixed a race condition during shutdown
when runtime threads have come parts of their way through detach, but still
depend on runtime resources, like GC memory. The fix added runtime threads
to the joinable thread list just before they vanished from mono_thread_manage
radar making sure shutdown waited upon the thread before cleaning up.

The above fix slightly changed the behavior of the finalizer thread since it
waits on joinable threads and will now potential block on threads still
executing code (that involves runtime resources). There’s was an assumption
around the threads on the joinable thread list that they should be very close
to complete when added, so join calls coming from the finalizer thread should
almost never block and if it does, the code that remains to execute should not
involve runtime operations risking deadlock situations. Adding the thread to
the list earlier than previously done expose the shutdown to some potential
theoretical problems.

To mitigate the risk and still solve the race condition this commit adds a
mechanism to keep track of active runtime threads until they park on joinable
thread list. The pending counter will be waited upon by the shutdown
thread, just before it does its regular wait on all joinable threads
(after finalizer thread has stopped) to make sure all runtime threads have
been added to the joinable thread list before waiting upon them. Threads are
added to the joinable thread as late as possible, exactly how it’s been done
in the past by sgen_client_thread_detach_with_lock. Shutdown thread will wait
on runtime threads to appear on the list for a short time and if timeout (pending
runtime thread count not reaching 0 before timeout), it will just print a warning
and continue shutdown.

Getting into a wait state during shutdown due to runtime threads not yet added to
joinable threads list should be very rare (hitting previous race condition that was rare),
triggering the timeout should be even more rare, and if that ever happens, we are exposed
to shutdown race condition as we have had in the past, but now we at least get a warning in
the log making it simpler to analyze further.

This commit also fixes a problem with the debugger thread hitting the same race condition as above.
The shutdown thread stopping the debugger thread didn't completely wait for it to stop using runtime
resources before continue shutdown sequence. This triggers the same race condition as when shutting
down regular runtime threads. This commit makes sure stop_debugger_thread waits on the debugger thread
handle to become signaled (happens at the very end of thread lifetime) before continuing the shutdown
logic.

* Generalize commit 0c6932a9 to support LDARG{0|1|2|3}, LDLOC{0|1|2|3}, LDARGS, LDLOCS, LDARG and LDLOC instead of LDLOC and LDLOCS. Improves generated code similar to issue #60945

source: https://github.com/mono/mono/pull/12595

Re-adding whitespace to reduce diff noise and make future cherrypicks easier.

* Validate the address that came from IDE using PointerValue. The IDE can send an invalid address and it was crashing mono.

Fixes #18191
Fixes #15612
Co-authored-by: NAleksey Kliger (λgeek) <akliger@gmail.com>

Wrap create_file_to_check_memory_address in #ifndef _MSC_VER check as it's only used in that scope.

Fixing an issue with ManagedWebSocket

The fix for 1256569 broke a test. Reverting most of that change and breaking the CreateLocal -> WinRTFallback -> CreateLocal loop by calling GetLocalTimeZoneInfoWinRTFallback instead of accessing Local from within FindSystemTimeZoneByIdWinRTFallback fixes both issues.

Need to make sure we don't duplicate the timezone and create a new local when we already have one.

Fixing a hang that would occur when there is incorrectly set time zone data in the windows registry. (case 1256569)

https://forum.unity.com/threads/current-netstandard-2-0-system-net-websocket-clientwebsocket-has-a-critical-bug.785366/

[corlib] Use Environment.Platform to access the platform, rather than probing the file system (#6535)

Alternatve patch to: #6533

https://forum.unity.com/threads/current-netstandard-2-0-system-net-websocket-clientwebsocket-has-a-critical-bug.785366/

* mono_custom_attrs_construct_by_type allows unity to have a chance at handling the error if one arises instead of fatally asserting
* mono_unity_error_convert_to_exception allows unity to take the provided MonoError and fetch the MonoException object within to log into the editor as the exception that was thrown.

This change has associated unity changes in order to fix (case 1255935)

Fixing hang that would occur when a Debugger.Break would be triggered while we are already processing a breakpoint. (case 1254123)

Adding test for debugger hang fix to case 1254123

Added a new property to Tests class which breaks this test.

Backport -> 2020.1, X509ChainImplUnityTls reports status now 

Fixes Fogbugz ticket 1261388.
Impl sticks close to current Mono Btls implementation on _master_ - the implementation on our fork has the same issues as prior to this fix and throws NotImplementedException

Emitting error 100 times is plenty.

This change applies a similar fix for exFAT partitions as was applied
for FAT32 partitions earlier. For exFAT partitions, the invalid inode
value seems to be 1 though.

* [debugger] Fixing two crashes while debugging an Android app.

-> Doing stepping into in VSM in some situation the frame saved in TLS is not synchronised with what is really been executed in the main thread. This makes the debugger-agent crashes because it tries to get variable info in some memory that is not available anymore.
	-> To fix it I forced the update of stack when CMD_THREAD_GET_FRAME_INFO is called.

-> Doing step over in Visual Studio for Windows, if you have the threads debugger window enabled, VSW calls frame_commands for each thread that is showed, and if the thread is not really_suspended it tries to get variable info from a memory that is not available anymore because the thread is not suspended yet.
	-> To fix it I don't send variable info of a frame if the thread is not really_suspended and doesn't have an async_state valid.

Cherry-picked with some light massaging by Alex Thibodeau (case 1249172)

Add System.Collections.Generic include to objects.cs

* Removing some asserts and returning err_invalid_argument with an error message when it's possible.

* if we don't find method get_ObjectIdForDebugger we try to find the property Task to continue async debug.

Cherry-picked by Alex Thibodeau with some moderate changes

* When we try to call a method to get the async_id to do an async debug and we are trying to do this in a generic method like this:

async Task<T> ExecuteAsync_Broken<T>()
 {
            await Task.Delay(2);
            return default;
  }

We need to inflate the generic type before call the method or we will get the error:  Could not execute the method because the containing type 'System.Runtime.CompilerServices.AsyncTaskMethodBuilder1[T_REF]’, is not fully instantiated.

Fixes #17549
Fixes #17569

Cherry-picked by Alex Thibodeau -- some light massaging required

Same method that ldloc.s uses, which incorporates the byref test.

When we have the following sequence:

    ldloc n
    ldfld valuetype [Unity.Mathematics]Unity.Mathematics.int2 Foo::bar

and local n is a reference to value, when walking the instructions in
mono_method_to_ir, we generally try to avoid loading a whole value
type just to load one of the fields.  I believe this is an
optimization.

The test here is not quite complete, though, as we have ref valuetypes
where the object stored at the location is actually an address, in
which case we still need to treat it as we would a normal reference.

This optimization isn't present in the ldloc.n coded forms and is
written in a slightly more robust way in ldloc.s, so no changes are
necessary there.

As an alternative to this commit, we might adopt the ldloc.s test for
ldloc as well, or merge in
https://github.com/mono/mono/commit/29428d951637ff85b593ea5c9cc5d5236579906d/mono/mini/method-to-ir.c
from master which encapsulates much the same intent.

This brings us in line with GetDiskFreeSpaceExW on Windows as well as .NET Core.

Attempting to guard against MONO_HANDLE_IS_NULL performing a null deref while checking for null. Sourced from: https://github.com/mono/mono/pull/9188 blindfix for case 1232819

sets.

Making associated change to type_in_image to also check the constrained type for a match. Re-adding asserts now they they no longer trigger.

updating to K&R coding convention

Fixes https://github.com/mono/mono/issues/18127.

- Changed the behavior on debugger-agent, if we can't parse the new behavior is to return invalid_argument and not assert and stop debugging
- Changed the mono_domain_set_fast before return from assembly_commands.
- Add error message when return INVALID_ARGUMENT

Fixes #19146

Fixes #8915

This change modifies the `ConcurrentBag` implementation from corefx.
Since we cannot update the corefx submodule, make a copy of the
ConcurrentBag.cs file, fix the issue, and point the build at this copy.

The change is in the `TrySteal` method. It makes calls on the
`CDSCollectionETWBCLProvider`, which is removed by the manged linker
by default. Those calls should be wrapped in a
`CDSCollectionETWBCLProvider.Log.IsEnabled()` if block, so the linker
can understand to not make the calls.