This implements the interactive trace start and stop methods.
This diff ended up being much larger than I anticipated because, by doing it, I found that I had implemented in the beginning many things in a non optimal way. In any case, the code is much better now.
There's a lot of boilerplate code due to the gdb-remote protocol, but the main changes are:
- New tracing packets: jLLDBTraceStop, jLLDBTraceStart, jLLDBTraceGetBinaryData. The gdb-remote packet definitions are quite comprehensive.
- Implementation of the "process trace start|stop" and "thread trace start|stop" commands.
- Implementaiton of an API in Trace.h to interact with live traces.
- Created an IntelPTDecoder for live threads, that use the debugger's stop id as checkpoint for its internal cache.
- Added a functionality to stop the process in case "process tracing" is enabled and a new thread can't traced.
- Added tests
I have some ideas to unify the code paths for post mortem and live threads, but I'll do that in another diff.
Differential Revision: https://reviews.llvm.org/D91679
This patch adds a test case to test AArch64 dynamic register sets.
This tests for the availability of certain register sets and query
their registers accordingly.
Reviewed By: labath, DavidSpickett
Differential Revision: https://reviews.llvm.org/D96463
This patch adds two new dynamic register sets for AArch64 MTE and
Pointer Authentication features. These register sets are dynamic and
will only be available if underlying hardware support either of these
features. LLDB will pull in Aux vector information and create register
infos based on that information.
A follow up patch will add a test case to test these feature registers.
Reviewed By: labath, DavidSpickett
Differential Revision: https://reviews.llvm.org/D96460
This is patch adds support for adding dynamic register sets for
AArch64 dynamic features in LLDB. AArch64 has optional features like
SVE, Pointer Authentication and MTE which means LLDB needs to decide
at run time which registers it needs to pull in for the current
executable based on underlying support for a certain feature.
This patch makes necessary adjustments to make way for dynamic
register infos and dynamic register sets.
Reviewed By: labath
Differential Revision: https://reviews.llvm.org/D96458
This patch fixes an issue, where if the thread has a signal blocked when
we try to inject it into the process (via vCont), then instead of
executing straight away, the injected signal will trigger another stop
when the thread unblocks the signal.
As (linux) threads start their life with SIGUSR1 (among others)
disabled, and only enable it during initialization, injecting the signal
during this window did not behave as expected. The fix is to change the
test to ensure the signal gets injected with the signal unblocked.
The simplest way to do this was to write a dedicated inferior for this
test. I also created a new header to factor out the function retrieving
the (os-specific) thread id.
As discussed on lldb-dev
<https://lists.llvm.org/pipermail/lldb-dev/2021-March/016777.html> the
mips code is unmaintained and untested. It also carries a lot of
technical debt which is not limited to mips-specific code.
Generic mips support remains (and is going to be used by the upcoming
freebsd code). Resurrecting mips support should be a matter of re-adding
the relevant register context files (while avoiding reintroducing the
debt).
Add a minimal support for the multiprocess extension in lldb-server.
The server indicates support for it via qSupported, and accepts
thread-ids containing a PID. However, it still does not support
debugging more than one inferior, so any other PID value results
in an error.
Differential Revision: https://reviews.llvm.org/D98482
TestVSCode_disconnect.test_launch fails with clean up error because
disconnect gets called twice once from the test case and once from
the tear down hook.
This patch disables disconnect after its been called from test_launch
Reviewed By: clayborg
Differential Revision: https://reviews.llvm.org/D99491
This is apparently allowed in Objective-C so we should test this in LLDB.
Reviewed By: teemperor
Differential Revision: https://reviews.llvm.org/D99513
This test is not useful as the functions it's testing are just returning
a constant. It also fails in unoptimized builds as it's comparing
character strings by address.
Remove the "depth" variable, as the same information can be obtained
through die_index_stack.size().
Also add a test case for a one tricky case I noticed -- a unit
containing only a null unit die.
When LLVM error handling was introduced to the parsing of the .debug_aranges it would cause major issues if any DWARFDebugArangeSet::extract() calls returned any errors. The code in DWARFDebugInfo::GetCompileUnitAranges() would end up calling DWARFDebugAranges::extract() which would return an error if _any_ DWARFDebugArangeSet had any errors, but it default constructed a DWARFDebugAranges object into DWARFDebugInfo::m_cu_aranges_up and populated it partially, and returned an error prior to finishing much needed functionality in the DWARFDebugInfo::GetCompileUnitAranges() function. Subsequent callers to this function would see that the DWARFDebugInfo::m_cu_aranges_up was actually valid and return this partially populated DWARFDebugAranges reference _and_ it would not be sorted or minimized.
This above bugs would cause an incomplete .debug_aranges parsing, it would skip manually parsing any compile units for ranges, and would not sort the DWARFDebugAranges in m_cu_aranges_up.
This bug would also cause breakpoints set by file and line to fail to set correctly if a symbol context for an address could not be resolved properly, which the incomplete and unsorted DWARFDebugAranges object that DWARFDebugInfo::GetCompileUnitAranges() returned would cause symbol context lookups resolved by address (breakpoint address) to fail to find any DWARF debug info for a given address.
This patch fixes all of the issues that I found:
- DWARFDebugInfo::GetCompileUnitAranges() no longer returns a "llvm::Expected<DWARFDebugAranges &>", but just returns a "const DWARFDebugAranges &". Why? Because this code contained a fallback that would parse all of the valid DWARFDebugArangeSet objects, and would check which compile units had valid .debug_aranges set entries, and manually build an address ranges table using DWARFUnit::BuildAddressRangeTable(). If we return an error because any DWARFDebugArangeSet has any errors, then we don't do any of this code. Now we parse all DWARFDebugArangeSet objects that have no errors, if any calls to DWARFDebugArangeSet::extract() return errors, we skip that DWARFDebugArangeSet so that we can use the fallback call to DWARFUnit::BuildAddressRangeTable(). Since DWARFDebugInfo::GetCompileUnitAranges() needs to parse what it can from the .debug_aranges and build address ranges tables for any compile units that don't have any .debug_aranges sets, everything now works as expected.
- Fix an issue where a DWARFDebugArangeSet contains multiple terminator entries. The LLVM parser and llvm-dwarfdump properly warn about this because it happens with linux compilers and linkers and was the original cause of the bug I am fixing here. We now correctly warn about this issue if "log enable dwarf info" is enabled, but we continue to parse the DWARFDebugArangeSet correctly so we don't lose data that is contained in the .debug_aranges section.
- DWARFDebugAranges::extract() no longer returns a llvm::Error because we need to be able to parse all of the valid DWARFDebugArangeSet objects. It also will correctly skip a DWARFDebugArangeSet object that has errors in the middle of the stream by setting the start offsets of each DWARFDebugArangeSet to be calculated by the previous DWARFDebugArangeSet::extract() calculated offset that uses the header which contains the length of the DWARFDebugArangeSet. This means if do we run into real errors while parsing individual DWARFDebugArangeSet objects, we can continue to parse the rest of the validly encoded DWARFDebugArangeSet objects in the .debug_aranges section. This will allow LLDB to parse DWARF that contains a possibly newer .debug_aranges set format than LLDB currently supports because we will error out for the parsing of the DWARFDebugArangeSet, but be able to skip to the next DWARFDebugArangeSet object using the "DWARFDebugArangeSet.m_header.length" field to calculate the next starting offset.
Tests were added to cover all new functionality.
Differential Revision: https://reviews.llvm.org/D99401
Print LLVM's pretty stack trace when lldb-vscode crashes. Also removes
the unnecessary call to PrintStackTraceOnErrorSignal in lldb-server as
it's already part of InitLLVM.
Differential revision: https://reviews.llvm.org/D99535
Move UpdateISAToDescriptorMap into ClassInfoExtractor so that all the
formerly public functions can be private and remain an implementation
detail of the extractor.
Differential revision: https://reviews.llvm.org/D99448
This is an LLDB test for the ASTImporter crash that got fixed in D99077.
The test is using Clang modules for the properties as it seems the conflicting
names are not actually correctly handled when generating debug information
(only the first property is emitted and the second one is ignored in the current
clang ToT).
Commit 6bc1e69de2 changed the search string
to also check for the generated strings that surround the plain assert:
Assertion `false && "lldb-test assert"' failed
^^^^^^^^^
This causes the test to fail on setups where the generated assert message
looks different. E.g., on macOS the generated message looks like this:
Assertion failed: (false && "lldb_assert failed"), function lldb_assert
This reverts the old behaviour of just checking for the actual string we
have inside LLDB.
LLDB on Linux built with symbols is showing this error.
Without symbols it still PASSes:
lldb-test: .../lldb/source/Utility/LLDBAssert.cpp:29: void lldb_private::lldb_assert(bool, const char *, const char *, const char *, unsigned int): Assertion `false && "lldb_assert failed"' failed.
With symbols it FAILs:
lldb-test: .../lldb/tools/lldb-test/lldb-test.cpp:1086: int opts::assert::lldb_assert(lldb_private::Debugger &): Assertion `false && "lldb-test assert"' failed.
Differential Revision: https://reviews.llvm.org/D99462
This adds the consistency I promised in D99315 between how we read the
class info from the Objective-C runtime and the shared cache. (NFC)
Differential revision: https://reviews.llvm.org/D99446
Generic classes in Swift have their name instantiated on request, since
the vast majority never need it, and it just wastes time and memory.
This results in LLDB being unable to determine the dynamic type of these
Swift objects.
The main issues is that lazily named classes are not added to the
gdb_objc_realized_classes hashtable. This means the class count in the
table doesn't change when a class is realized and LLDB doesn't know it
needs to re-parse the class info. But even if it did, the classes are
not in the hash table.
The first change in this patch is that we read
objc_debug_realized_class_generation_count and re-parse the class info
when the count changes.
The second change in this patch is that we use
objc_copyRealizedClassList (if available) to get all realized classes
from the runtime.
Unfortunately, objc_copyRealizedClassList calls _dyld_objc_class_count
in its implementation. As we know, the Objective-C parsing code might
get called before dyld is fully initialized, resulting in crashes or
even a stranded lock. Therefore we only use objc_copyRealizedClassList
when we know it's safe to do so by checking libSystemInitialized in
dyld_all_image_infos.
As a result, it's possible that the first time we read the Objective-C
runtime we are forced to use gdb_objc_realized_classes. This should be
fine, as there should be no lazily named classes at this point.
Subsequent queries will detect the change in realized class generation
count and use objc_copyRealizedClassList.
This patch keeps the old behavior when objc_copyRealizedClassList or
objc_debug_realized_class_generation_count are not available.
Differential revision: https://reviews.llvm.org/D99315
On Darwin based systems, lldb will get notified by dyld before it itself
finished initializing, at which point it's not safe to call certain APIs
or SPIs. Add a method to the DynamicLoader to query that.
Differential revision: https://reviews.llvm.org/D99314
In future patches I will be setting the IsText parameter frequently so I will refactor the args to be in the following order. I have removed the FileSize parameter because it is never used.
```
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getFile(const Twine &Filename, bool IsText = false,
bool RequiresNullTerminator = true, bool IsVolatile = false);
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getFileOrSTDIN(const Twine &Filename, bool IsText = false,
bool RequiresNullTerminator = true);
static ErrorOr<std::unique_ptr<MB>>
getFileAux(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
bool IsText, bool RequiresNullTerminator, bool IsVolatile);
static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
getFile(const Twine &Filename, bool IsVolatile = false);
```
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D99182
The objc_debug_isa_class_mask magic value that the objc runtime vends
is now initialized using a static initializer instead of a constant
value. The runtime plugin itself will be initialized before the value
is computed and as a result, the cache will get the wrong value.
Making the creation of the NonPointerIsaCache fully lazy fixes this.
LLDB can often appear deadlocked to users that use IDEs when it is indexing DWARF, or parsing symbol tables. These long running operations can make a debug session appear to be doing nothing even though a lot of work is going on inside LLDB. This patch adds a public API to allow clients to listen to debugger events that report progress and will allow UI to create an activity window or display that can show users what is going on and keep them informed of expensive operations that are going on inside LLDB.
Differential Revision: https://reviews.llvm.org/D97739
The commit passes the tests on Darwin. The failure on linux shows
that this change was not sufficient to get this setting to work on linux,
but the behavior is the same as before the patch & test, and it caused
no new failures.
So marking the tests as Darwin only till someone can debug the Linux
issue.
The StopInfoBreakpoint::PerformAction was overriding the synchronous
breakpoint's ShouldStop report. Fix that and add a test.
This fixes two bugs in the original submission:
1) Actually generate both dylibs by including the second one in the Makefile
2) Don't ask synchronous callbacks for their opinion on whether to stop
in the async context, that info is taken care of by recording the m_should_stop
on entry to PerformAction.
Differential Revision: https://reviews.llvm.org/D98914
This patch introduces Scripted Processes to lldb.
The goal, here, is to be able to attach in the debugger to fake processes
that are backed by script files (in Python, Lua, Swift, etc ...) and
inspect them statically.
Scripted Processes can be used in cooperative multithreading environments
like the XNU Kernel or other real-time operating systems, but it can
also help us improve the debugger testing infrastructure by writting
synthetic tests that simulates hard-to-reproduce process/thread states.
Although ScriptedProcess is not feature-complete at the moment, it has
basic execution capabilities and will improve in the following patches.
rdar://65508855
Differential Revision: https://reviews.llvm.org/D95713
Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>
This got removed in 68bb51acd5 and this enabled
the test on macOS (where it just causes lldb-server to crash). Re-adding the
decorator to get the tests passing again.
Depending on include order, these can cause build errors when
including the llvm MachO.h where these are defined as enums.
Update the list to include some more names.
DWARFExpression implements the DWARF2 expression model that left
ambiguity on whether the result of an expression was a value or an
address. This patch implements the DWARF location description model
introduces in DWARF 4 and sets the result Value's kind accordingly, if
the expression comes from a DWARF v4+ compile unit. The nomenclature
is taken from DWARF 5, chapter 2.6 "Location Descriptions".
Differential Revision: https://reviews.llvm.org/D98996
This patch introduces Scripted Processes to lldb.
The goal, here, is to be able to attach in the debugger to fake processes
that are backed by script files (in Python, Lua, Swift, etc ...) and
inspect them statically.
Scripted Processes can be used in cooperative multithreading environments
like the XNU Kernel or other real-time operating systems, but it can
also help us improve the debugger testing infrastructure by writting
synthetic tests that simulates hard-to-reproduce process/thread states.
Although ScriptedProcess is not feature-complete at the moment, it has
basic execution capabilities and will improve in the following patches.
rdar://65508855
Differential Revision: https://reviews.llvm.org/D95713
Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>
In order to facilitate the writting of Scripted Processes, this patch
introduces a `ScriptedProcess` python base class in the lldb module.
The base class holds the python interface with all the - abstract -
methods that need to be implemented by the inherited class but also some
methods that can be overwritten.
This patch also provides an example of a Scripted Process with the
`MyScriptedProcess` class.
rdar://65508855
Differential Revision: https://reviews.llvm.org/D95712
Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>
This patch adds a ScriptedProcess interface to the ScriptInterpreter and
more specifically, to the ScriptInterpreterPython.
This interface will be used in the C++ `ScriptProcess` Process Plugin to
call the script methods.
At the moment, not all methods are implemented, they will upstreamed in
upcoming patches.
This patch also adds helper methods to the ScriptInterpreter to
convert `SBAPI` Types (SBData & SBError) to `lldb_private` types
(DataExtractor & Status).
rdar://65508855
Differential Revision: https://reviews.llvm.org/D95711
Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>
This patch adds a new command options to the CommandObjectProcessLaunch
for scripted processes.
Among the options, the user need to specify the class name managing the
scripted process. The user can also use a key-value dictionary holding
arbitrary data that will be passed to the managing class.
This patch also adds getters and setters to `SBLaunchInfo` for the
class name managing the scripted process and the dictionary.
rdar://65508855
Differential Review: https://reviews.llvm.org/D95710
Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>
The file contained bogus input - the DIE list was not properly
terminated. This should not cause a crash, but it seems it was crashing
at least on linux arm and x86 windows.
lit has grown a feature where it stores the runtimes of all tests.
Normally, these times should be stored in the build directory, but
because our API tests have set test_exec_root to point to the source
tree, it has ended up polluting our checkout and led to the
.lit_test_times.txt being committed to the repository.
Delete this file, and adjust the exec root of API tests. I've also
needed to adjust the root of Shell tests, in order to avoid the two
overlapping.
SymbolFileDWARF::ResolveSymbolContext is currently unaware that in DWARF5 the primary file is specified at file index 0. As a result it misses to correctly resolve the symbol context for the primary file when DWARF5 debug data is used and the primary file is only specified at index 0.
This change makes use of CompileUnit::ResolveSymbolContext to resolve the symbol context. The ResolveSymbolContext in CompileUnit has been previously already updated to reflect changes in DWARF5
and contains a more readable version. It can resolve more, but will also do a bit more work than
SymbolFileDWARF::ResolveSymbolContext (getting the Module, and going through SymbolFileDWARF::ResolveSymbolContextForAddress), however, it's mostly directed by $resolve_scope
what will be resolved, and ensures that code is easier to maintain if there's only one path.
Reviewed By: labath
Differential Revision: https://reviews.llvm.org/D98619
In general, it seems like the debugger should allow programs to load & run with
libraries as far as possible, instead of defaulting to being super-picky about
unavailable symbols.
This is critical on macOS/Darwin, as libswiftCore.dylib may 1) export a version
symbol using @available markup and then 2) expect that other exported APIs are
only dynamically used once the version symbol is checked. We can't open a
version of the library built with a bleeding-edge SDK on an older OS without
RTLD_LAXY (or pervasive/expensive @available markup added to dyld APIs).
This was previously committed as cb8c1ee269 and reverted due to
unknown failures on the Linux bots. This version adds additional asserts
to check that the shared objects are where we expect them & that calling
f1() from libt1 produces the expected value. The Linux failure is
tracked by https://bugs.llvm.org/show_bug.cgi?id=49656.
See: https://lists.llvm.org/pipermail/lldb-dev/2021-March/016796.html
Differential Revision: https://reviews.llvm.org/D98879
In general, it seems like the debugger should allow programs to load & run with
libraries as far as possible, instead of defaulting to being super-picky about
unavailable symbols.
This is critical on macOS/Darwin, as libswiftCore.dylib may 1) export a version
symbol using @available markup and then 2) expect that other exported APIs are
only dynamically used once the version symbol is checked. We can't open a
version of the library built with a bleeding-edge SDK on an older OS without
RTLD_LAXY (or pervasive/expensive @available markup added to dyld APIs).
See: https://lists.llvm.org/pipermail/lldb-dev/2021-March/016796.html
Differential Revision: https://reviews.llvm.org/D98879
Call `os_log_fault` when an lldb assert fails. We piggyback off
`LLVM_SUPPORT_XCODE_SIGNPOSTS`, which also depends on `os_log`, to avoid
having to introduce another CMake check and corresponding define.
This patch also adds a small test using lldb-test that verifies we abort
with a "regular" assertion when asserts are enabled.
Differential revision: https://reviews.llvm.org/D98987
This reverts commit 9406d43138.
I messed up a test, and when I got it right it was failing. The changed logic
doesn't work quite right (now the async callback called at sync time is
forcing us to stop. I need to be a little more careful about that.
We weren't taking into account the "m_should_stop" setting that the
synchronous breakpoint callback had already set when we did PerformAction
in the StopInfoBreakpoint. So we didn't obey its instructions when it
told us to stop. Fixed that and added some tests both for when we
just have the setting, and when we have the setting AND other breakpoints
at the shared library load notification breakpoint address.
Differential Revision: https://reviews.llvm.org/D98914
Make the API, Shell and Unit tests independent lit test suites. This
allows us to specify different dependencies and skip rebuilding all the
unit test (which is particularly expensive) when running check-lldb-api
or check-lldb-shell.
This does not change the autogenerated targets such as
check-lldb-shell-driver or the top level check-lldb target, which all
continue to work as before.
Differential revision: https://reviews.llvm.org/D98842
TestExitDuringExpression test_exit_before_one_thread_unwind fails
sporadically on both Arm and AArch64 linux buildbots.
This seems like a thread timing issue. I am marking it skip for now.
For instance, some recent clang emits this code on x86_64:
0x100002b99 <+57>: callq 0x100002b40 ; step_out_of_here at main.cpp:11
-> 0x100002b9e <+62>: xorl %eax, %eax
0x100002ba0 <+64>: popq %rbp
0x100002ba1 <+65>: retq
and the "xorl %eax, %eax" is attributed to the same line as the callq. Since
step out is supposed to stop just on returning from the function, you can't guarantee
it will end up on the next line. I changed the test to check that we were either
on the call line or on the next line, since either would be right depending on the
debug information.
The cause is the non-async-signal-safety printf function (et al.). If
the test managed to interrupt the process and inject a signal before the
printf("@started") call returned (but after it has actually written the
output), that string could end up being printed twice (presumably,
because the function did not manage the clear the userspace buffer, and
so the print call in the signal handler would print it once again).
This patch fixes the issue by replacing the printf call in the signal
handler with a sprintf+write combo, which should not suffer from that
problem (though I wouldn't go as far as to call it async signal safe).
Fix the test to account for recent test infrastructure changes, and make
it run locally to increase the chances of it continuing to work in the
future.
The TestGdbRemote_vContThreads.py were introduced to test NetBSD process
plugin's capability of sending per-thread and per-process signals.
However, at some point the tests started failing. From retrospective,
it is possible that they were relying on some bug in the plugin's
original signal handling.
Fix the tests not to expect the process to terminate after receiving
the signals. Instead, scan for output indicating that the signals were
received and match thread IDs in it. Enable 'signal to all threads'
test everywhere as it works fine on Linux. Add a new test for vCont
packet without specific thread IDs. Introduce a helper function
to cover the common part of tests.
While this does not fix all the problems on NetBSD, it enables a subset
of the tests on other systems. I am planning to add more tests
to the group while implementing multiprocess extension for vCont.
Differential Revision: https://reviews.llvm.org/D98749
The idiom:
```
DeclContext::lookup_result R = DeclContext::lookup(Name);
for (auto *D : R) {...}
```
is not safe when in the loop body we trigger deserialization from an AST file.
The deserialization can insert new declarations in the StoredDeclsList whose
underlying type is a vector. When the vector decides to reallocate its storage
the pointer we hold becomes invalid.
This patch replaces a SmallVector with an singly-linked list. The current
approach stores a SmallVector<NamedDecl*, 4> which is around 8 pointers.
The linked list is 3, 5, or 7. We do better in terms of memory usage for small
cases (and worse in terms of locality -- the linked list entries won't be near
each other, but will be near their corresponding declarations, and we were going
to fetch those memory pages anyway). For larger cases: the vector uses a
doubling strategy for reallocation, so will generally be between half-full and
full. Let's say it's 75% full on average, so there's N * 4/3 + 4 pointers' worth
of space allocated currently and will be 2N pointers with the linked list. So we
break even when there are N=6 entries and slightly lose in terms of memory usage
after that. We suspect that's still a win on average.
Thanks to @rsmith!
Differential revision: https://reviews.llvm.org/D91524
Summary:
The request "evaluate" supports a "context" attribute, which is sent by VSCode. The attribute is defined here https://microsoft.github.io/debug-adapter-protocol/specification#Requests_Evaluate
The "clipboard" context is not yet supported by lldb-vscode, so we can forget about it for now. The 'repl' (i.e. Debug Console) and 'watch' (i.e. Watch Expression) contexts must use the expression parser in case the frame's variable path is not enough, as the user expects these expressions to never fail. On the other hand, the 'hover' expression is invoked whenever the user hovers on any keyword on the UI and the user is fine with the expression not being fully resolved, as they know that the 'repl' case is the fallback they can rely on.
Given that the 'hover' expression is invoked many many times without the user noticing it due to it being triggered by the mouse, I'm making it use only the frame's variable path functionality and not the expression parser. This should speed up tremendously the responsiveness of a debug session when the user only sets source breakpoints and inspect local variables, as the entire debug info is not needed to be parsed.
Regarding tests, I've tried to be as comprehensive as possible considering a multi-file project. Fortunately, the results from the "hover" case are enough most of the times.
Differential Revision: https://reviews.llvm.org/D98656
TestExitDuringExpression test_exit_before_one_thread_unwind fails
sporadically on arm/linux. This seems like a thread timing issue.
I am marking it skip for now.
Muhammad Omair Javaid