Prior to this patch, SBFrame/SBThread methods exhibit racy behavior if
called while the process is running, because they do not lock the
`Process::RetRunLock` mutex. If they did, they would fail, correctly
identifying that the process is not running.
Some methods _attempt_ to protect against this with the pattern:
```
ExecutionContext exe_ctx(m_opaque_sp.get(), lock); // this is a different lock
Process *process = exe_ctx.GetProcessPtr();
if (process) {
Process::StopLocker stop_locker;
if (stop_locker.TryLock(&process->GetRunLock()))
.... do work ...
```
However, this is also racy: the constructor of `ExecutionContext` will
access the frame list, which is something that can only be done once the
process is stopped.
With this patch:
1. The constructor of `ExecutionContext` now expects a `ProcessRunLock`
as an argument. It attempts to lock the run lock, and only fills in
information about frames and threads if the lock can be acquired.
Callers of the constructor are expected to check the lock.
2. All uses of ExecutionContext are adjusted to conform to the above.
3. The SBThread.cpp-defined helper function ResumeNewPlan now expects a
locked ProcessRunLock as _proof_ that the execution is stopped. It will
unlock the mutex prior to resuming the process.
This commit exposes many opportunities for early-returns, but these
would increase the diff of this patch and distract from the important
changes, so we opt not to do it here.
I am using VSCode with the official vscode-lldb extension. When I try to list the breakpoints in the debug console get the message: ``` br list can't evaluate expressions when the process is running. ``` I know that this is wrong and you need to use ``` `br list (lldb) br list No breakpoints currently set. ``` but the error message is misleading. I cleaned up the code and now the error message is ``` br list sbframe object is not valid. ``` which is still not perfect, but at least it's not misleading.
But one made in a situation where that's impossible might only have an error, and no symbol context, so that's not necessarily true. Check for the target's validity before using it. Fixes issue #93313
Flaky on the bot: https://lab.llvm.org/buildbot/#/builders/96/builds/54435
This has been flaky for a while, for example https://lab.llvm.org/buildbot/#/builders/96/builds/50350 ``` Command Output (stdout): -- lldb version 18.0.0git (https://github.com/llvm/llvm-project.git revision 3974d89bde66a2ec61261b969b51993da81205c7) clang revision 3974d89bde66a2ec61261b969b51993da81205c7 llvm revision 3974d89bde66a2ec61261b969b51993da81205c7 "can't evaluate expressions when the process is running." ``` ``` PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace. #0 0x0000ffffa46191a0 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x529a1a0) #1 0x0000ffffa4617144 llvm::sys::RunSignalHandlers() (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x5298144) #2 0x0000ffffa46198d0 SignalHandler(int) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x529a8d0) #3 0x0000ffffab25b7dc (linux-vdso.so.1+0x7dc) #4 0x0000ffffab13d050 /build/glibc-Q8DG8B/glibc-2.31/string/../sysdeps/aarch64/multiarch/memcpy_advsimd.S:92:0 #5 0x0000ffffa446f420 lldb_private::process_gdb_remote::GDBRemoteRegisterContext::PrivateSetRegisterValue(unsigned int, llvm::ArrayRef<unsigned char>) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x50f0420) #6 0x0000ffffa446f7b8 lldb_private::process_gdb_remote::GDBRemoteRegisterContext::GetPrimordialRegister(lldb_private::RegisterInfo const*, lldb_private::process_gdb_remote::GDBRemoteCommunicationClient&) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x50f07b8) #7 0x0000ffffa446f308 lldb_private::process_gdb_remote::GDBRemoteRegisterContext::ReadRegisterBytes(lldb_private::RegisterInfo const*) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x50f0308) #8 0x0000ffffa446ec1c lldb_private::process_gdb_remote::GDBRemoteRegisterContext::ReadRegister(lldb_private::RegisterInfo const*, lldb_private::RegisterValue&) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x50efc1c) #9 0x0000ffffa412eaa4 lldb_private::RegisterContext::ReadRegisterAsUnsigned(lldb_private::RegisterInfo const*, unsigned long) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x4dafaa4) #10 0x0000ffffa420861c ReadLinuxProcessAddressMask(std::shared_ptr<lldb_private::Process>, llvm::StringRef) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x4e8961c) #11 0x0000ffffa4208430 ABISysV_arm64::FixCodeAddress(unsigned long) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x4e89430) ``` Judging by the backtrace something is trying to read the pointer authentication address/code mask registers. This explains why I've not seen this issue locally, as the buildbot runs on Graviton 3 with has the pointer authentication extension. I will try to reproduce, fix and re-enable the test.
This is an ongoing series of commits that are reformatting our Python code. Reformatting is done with `black` (23.1.0). If you end up having problems merging this commit because you have made changes to a python file, the best way to handle that is to run `git checkout --ours <yourfile>` and then reformat it with black. RFC: https://discourse.llvm.org/t/rfc-document-and-standardize-python-code-style Differential revision: https://reviews.llvm.org/D151460
TestRunLocker.py is failing on windows x64 and AArch64 buildbots. Buildbot log suggests that test needs some minor modification for windows which I will do later. https://lab.llvm.org/buildbot/#/builders/83/builds/29680 https://lab.llvm.org/buildbot/#/builders/219/builds/942
This reverts commit 9d28e00e741cb19684111656803434aceef4c2a0.