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[lldb] Expose the Target API mutex through the SB API
Expose u target API mutex through the SB API. This is motivated by lldb-dap, which is built on top of the SB API and needs a way to execute a series of SB API calls in an atomic manner (see llvm#131242). We can solve this problem by either introducing an additional layer of locking at the DAP level or by exposing the existing locking at the SB API level. This patch implements the second approach. This was discussed in an RFC on Discourse [0]. The original implementation exposed a move-only lock rather than a mutex [1] which doesn't work well with SWIG 4.0 [2]. This implement the alternative solution of exposing the mutex rather than the lock. The SBMutex conforms to the BasicLockable requirement [3] (which is why the methods are called `lock` and `unlock` rather than Lock and Unlock) so it can be used as `std::lock_guard<lldb::SBMutex>` and `std::unique_lock<lldb::SBMutex>`. [0]: https://discourse.llvm.org/t/rfc-exposing-the-target-api-lock-through-the-sb-api/85215/6 [1]: llvm#131404 [2]: https://discourse.llvm.org/t/rfc-bumping-the-minimum-swig-version-to-4-1-0/85377/9 [3]: https://en.cppreference.com/w/cpp/named_req/BasicLockable
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13 files changed

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‎lldb/bindings/interface/SBMutexExtensions.i‎

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%extend lldb::SBMutex {
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#ifdef SWIGPYTHON
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%pythoncode %{
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def __enter__(self):
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self.lock()
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return self
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def __exit__(self, exc_type, exc_value, traceback):
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self.unlock()
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%}
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#endif
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}

‎lldb/bindings/interfaces.swig‎

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@@ -51,6 +51,7 @@
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%include "./interface/SBMemoryRegionInfoListDocstrings.i"
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%include "./interface/SBModuleDocstrings.i"
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%include "./interface/SBModuleSpecDocstrings.i"
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%include "./interface/SBMutexExtensions.i"
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%include "./interface/SBPlatformDocstrings.i"
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%include "./interface/SBProcessDocstrings.i"
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%include "./interface/SBProcessInfoDocstrings.i"
@@ -121,15 +122,16 @@
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%include "lldb/API/SBHostOS.h"
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%include "lldb/API/SBInstruction.h"
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%include "lldb/API/SBInstructionList.h"
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%include "lldb/API/SBLanguages.h"
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%include "lldb/API/SBLanguageRuntime.h"
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%include "lldb/API/SBLanguages.h"
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%include "lldb/API/SBLaunchInfo.h"
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%include "lldb/API/SBLineEntry.h"
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%include "lldb/API/SBListener.h"
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%include "lldb/API/SBMemoryRegionInfo.h"
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%include "lldb/API/SBMemoryRegionInfoList.h"
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%include "lldb/API/SBModule.h"
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%include "lldb/API/SBModuleSpec.h"
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%include "lldb/API/SBMutex.h"
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%include "lldb/API/SBPlatform.h"
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%include "lldb/API/SBProcess.h"
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%include "lldb/API/SBProcessInfo.h"

‎lldb/include/lldb/API/LLDB.h‎

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@@ -50,6 +50,7 @@
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#include "lldb/API/SBMemoryRegionInfoList.h"
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#include "lldb/API/SBModule.h"
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#include "lldb/API/SBModuleSpec.h"
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#include "lldb/API/SBMutex.h"
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#include "lldb/API/SBPlatform.h"
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#include "lldb/API/SBProcess.h"
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#include "lldb/API/SBProcessInfo.h"

‎lldb/include/lldb/API/SBDefines.h‎

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@@ -89,6 +89,7 @@ class LLDB_API SBMemoryRegionInfoList;
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class LLDB_API SBModule;
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class LLDB_API SBModuleSpec;
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class LLDB_API SBModuleSpecList;
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class LLDB_API SBMutex;
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class LLDB_API SBPlatform;
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class LLDB_API SBPlatformConnectOptions;
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class LLDB_API SBPlatformShellCommand;

‎lldb/include/lldb/API/SBMutex.h‎

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//===-- SBMutex.h
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//----------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLDB_API_SBLOCK_H
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#define LLDB_API_SBLOCK_H
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#include "lldb/API/SBDefines.h"
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#include "lldb/lldb-forward.h"
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#include <mutex>
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namespace lldb {
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/// A general-purpose lock in the SB API. The lock can be locked and unlocked.
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/// The default constructed lock is unlocked, but generally the lock is locked
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/// when it is returned from a class.
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class LLDB_API SBMutex {
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public:
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SBMutex();
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SBMutex(const SBMutex &rhs);
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const SBMutex &operator=(const SBMutex &rhs);
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~SBMutex();
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/// Returns true if this lock has ownership of the underlying mutex.
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bool IsValid() const;
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/// Blocking operation that takes ownership of this lock.
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void lock() const;
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/// Releases ownership of this lock.
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void unlock() const;
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private:
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// Private constructor used by SBTarget to create the Target API mutex.
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// Requires a friend declaration.
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SBMutex(lldb::TargetSP target_sp);
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friend class SBTarget;
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std::shared_ptr<std::recursive_mutex> m_opaque_sp;
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};
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#endif
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} // namespace lldb

‎lldb/include/lldb/API/SBTarget.h‎

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@@ -342,7 +342,7 @@ class LLDB_API SBTarget {
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uint32_t GetAddressByteSize();
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const char *GetTriple();
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const char *GetABIName();
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const char *GetLabel() const;
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/// An error if a Trace already exists or the trace couldn't be created.
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lldb::SBTrace CreateTrace(SBError &error);
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lldb::SBMutex GetAPIMutex() const;
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protected:
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friend class SBAddress;
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friend class SBAddressRange;

‎lldb/include/lldb/Target/Target.h‎

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@@ -1692,6 +1692,22 @@ class Target : public std::enable_shared_from_this<Target>,
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}
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};
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/// The private implementation backing SBLock.
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class APILock {
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public:
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APILock(std::shared_ptr<std::recursive_mutex> mutex_sp)
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: m_mutex(std::move(mutex_sp)), m_lock(*m_mutex) {}
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void Lock() { m_lock.lock(); }
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void Unlock() { m_lock.unlock(); }
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operator bool() const { return static_cast<bool>(m_lock); }
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private:
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std::shared_ptr<std::recursive_mutex> m_mutex;
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std::unique_lock<std::recursive_mutex> m_lock;
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};
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} // namespace lldb_private
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#endif // LLDB_TARGET_TARGET_H

‎lldb/source/API/CMakeLists.txt‎

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@@ -81,6 +81,7 @@ add_lldb_library(liblldb SHARED ${option_framework}
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SBMemoryRegionInfoList.cpp
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SBModule.cpp
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SBModuleSpec.cpp
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SBMutex.cpp
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SBPlatform.cpp
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SBProcess.cpp
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SBProcessInfo.cpp

‎lldb/source/API/SBMutex.cpp‎

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//===-- SBMutex.cpp
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//--------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "lldb/API/SBMutex.h"
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#include "lldb/Target/Target.h"
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#include "lldb/Utility/Instrumentation.h"
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#include "lldb/lldb-forward.h"
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#include <memory>
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#include <mutex>
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using namespace lldb;
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using namespace lldb_private;
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SBMutex::SBMutex() { LLDB_INSTRUMENT_VA(this); }
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SBMutex::SBMutex(const SBMutex &rhs) : m_opaque_sp(rhs.m_opaque_sp) {
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LLDB_INSTRUMENT_VA(this);
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}
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const SBMutex &SBMutex::operator=(const SBMutex &rhs) {
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LLDB_INSTRUMENT_VA(this);
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m_opaque_sp = rhs.m_opaque_sp;
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return *this;
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}
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SBMutex::SBMutex(lldb::TargetSP target_sp)
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: m_opaque_sp(std::shared_ptr<std::recursive_mutex>(
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target_sp, &target_sp->GetAPIMutex())) {
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LLDB_INSTRUMENT_VA(this, target_sp);
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}
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SBMutex::~SBMutex() { LLDB_INSTRUMENT_VA(this); }
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bool SBMutex::IsValid() const {
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LLDB_INSTRUMENT_VA(this);
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return static_cast<bool>(m_opaque_sp);
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}
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void SBMutex::lock() const {
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LLDB_INSTRUMENT_VA(this);
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if (m_opaque_sp)
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m_opaque_sp->lock();
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}
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void SBMutex::unlock() const {
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LLDB_INSTRUMENT_VA(this);
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if (m_opaque_sp)
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m_opaque_sp->unlock();
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}

‎lldb/source/API/SBTarget.cpp‎

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@@ -7,10 +7,6 @@
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//===----------------------------------------------------------------------===//
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#include "lldb/API/SBTarget.h"
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#include "lldb/Utility/Instrumentation.h"
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#include "lldb/Utility/LLDBLog.h"
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#include "lldb/lldb-public.h"
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#include "lldb/API/SBBreakpoint.h"
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#include "lldb/API/SBDebugger.h"
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#include "lldb/API/SBEnvironment.h"
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#include "lldb/API/SBListener.h"
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#include "lldb/API/SBModule.h"
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#include "lldb/API/SBModuleSpec.h"
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#include "lldb/API/SBMutex.h"
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#include "lldb/API/SBProcess.h"
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#include "lldb/API/SBSourceManager.h"
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#include "lldb/API/SBStream.h"
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#include "lldb/Utility/ArchSpec.h"
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#include "lldb/Utility/Args.h"
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#include "lldb/Utility/FileSpec.h"
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#include "lldb/Utility/Instrumentation.h"
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#include "lldb/Utility/LLDBLog.h"
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#include "lldb/Utility/ProcessInfo.h"
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#include "lldb/Utility/RegularExpression.h"
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#include "lldb/ValueObject/ValueObjectConstResult.h"
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#include "lldb/ValueObject/ValueObjectList.h"
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#include "lldb/ValueObject/ValueObjectVariable.h"
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#include "lldb/lldb-public.h"
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#include "Commands/CommandObjectBreakpoint.h"
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#include "lldb/Interpreter/CommandReturnObject.h"
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}
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return SBTrace();
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}
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lldb::SBMutex SBTarget::GetAPIMutex() const {
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LLDB_INSTRUMENT_VA(this);
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2446+
if (TargetSP target_sp = GetSP())
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return lldb::SBMutex(target_sp);
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return lldb::SBMutex();
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}

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