From: Jim Ingham Date: Fri, 29 Mar 2019 17:07:30 +0000 (+0000) Subject: Use the multi-lockable form of std::lock for operator= X-Git-Tag: llvmorg-10-init~8882 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=cdd4892f12e860905565f4e4444d7726618f89bd;p=platform%2Fupstream%2Fllvm.git Use the multi-lockable form of std::lock for operator= For = operators for lists that have mutexes, we were either just taking the locks sequentially or hand-rolling a trick to try to avoid lock inversion. Use the std::lock mechanism for this instead. Differential Revision: https://reviews.llvm.org/D59957 llvm-svn: 357276 --- diff --git a/lldb/include/lldb/Core/ModuleSpec.h b/lldb/include/lldb/Core/ModuleSpec.h index 16a8cfa..ab0f4e9 100644 --- a/lldb/include/lldb/Core/ModuleSpec.h +++ b/lldb/include/lldb/Core/ModuleSpec.h @@ -311,8 +311,10 @@ public: ModuleSpecList &operator=(const ModuleSpecList &rhs) { if (this != &rhs) { - std::lock_guard lhs_guard(m_mutex); - std::lock_guard rhs_guard(rhs.m_mutex); + std::lock(m_mutex, rhs.m_mutex); + std::lock_guard lhs_guard(m_mutex, std::adopt_lock); + std::lock_guard rhs_guard(rhs.m_mutex, + std::adopt_lock); m_specs = rhs.m_specs; } return *this; diff --git a/lldb/include/lldb/Utility/StreamTee.h b/lldb/include/lldb/Utility/StreamTee.h index 43e99ac..92e94d4 100644 --- a/lldb/include/lldb/Utility/StreamTee.h +++ b/lldb/include/lldb/Utility/StreamTee.h @@ -49,8 +49,11 @@ public: StreamTee &operator=(const StreamTee &rhs) { if (this != &rhs) { Stream::operator=(rhs); - std::lock_guard lhs_locker(m_streams_mutex); - std::lock_guard rhs_locker(rhs.m_streams_mutex); + std::lock(m_streams_mutex, rhs.m_streams_mutex); + std::lock_guard lhs_locker(m_streams_mutex, + std::adopt_lock); + std::lock_guard rhs_locker(rhs.m_streams_mutex, + std::adopt_lock); m_streams = rhs.m_streams; } return *this; diff --git a/lldb/source/Breakpoint/BreakpointLocationCollection.cpp b/lldb/source/Breakpoint/BreakpointLocationCollection.cpp index 413c12a..0651ca0 100644 --- a/lldb/source/Breakpoint/BreakpointLocationCollection.cpp +++ b/lldb/source/Breakpoint/BreakpointLocationCollection.cpp @@ -181,17 +181,11 @@ void BreakpointLocationCollection::GetDescription( BreakpointLocationCollection &BreakpointLocationCollection::operator=( const BreakpointLocationCollection &rhs) { - // Same trick as in ModuleList to avoid lock inversion. if (this != &rhs) { - if (uintptr_t(this) > uintptr_t(&rhs)) { - std::lock_guard lhs_guard(m_collection_mutex); - std::lock_guard rhs_guard(rhs.m_collection_mutex); + std::lock(m_collection_mutex, rhs.m_collection_mutex); + std::lock_guard lhs_guard(m_collection_mutex, std::adopt_lock); + std::lock_guard rhs_guard(rhs.m_collection_mutex, std::adopt_lock); m_break_loc_collection = rhs.m_break_loc_collection; - } else { - std::lock_guard lhs_guard(m_collection_mutex); - std::lock_guard rhs_guard(rhs.m_collection_mutex); - m_break_loc_collection = rhs.m_break_loc_collection; - } } return *this; } diff --git a/lldb/source/Core/ModuleList.cpp b/lldb/source/Core/ModuleList.cpp index 8740bd0..d59e429 100644 --- a/lldb/source/Core/ModuleList.cpp +++ b/lldb/source/Core/ModuleList.cpp @@ -130,25 +130,12 @@ ModuleList::ModuleList(ModuleList::Notifier *notifier) const ModuleList &ModuleList::operator=(const ModuleList &rhs) { if (this != &rhs) { - // That's probably me nit-picking, but in theoretical situation: - // - // * that two threads A B and - // * two ModuleList's x y do opposite assignments ie.: - // - // in thread A: | in thread B: - // x = y; | y = x; - // - // This establishes correct(same) lock taking order and thus avoids - // priority inversion. - if (uintptr_t(this) > uintptr_t(&rhs)) { - std::lock_guard lhs_guard(m_modules_mutex); - std::lock_guard rhs_guard(rhs.m_modules_mutex); - m_modules = rhs.m_modules; - } else { - std::lock_guard lhs_guard(m_modules_mutex); - std::lock_guard rhs_guard(rhs.m_modules_mutex); - m_modules = rhs.m_modules; - } + std::lock(m_modules_mutex, rhs.m_modules_mutex); + std::lock_guard lhs_guard(m_modules_mutex, + std::adopt_lock); + std::lock_guard rhs_guard(rhs.m_modules_mutex, + std::adopt_lock); + m_modules = rhs.m_modules; } return *this; } diff --git a/lldb/source/Target/SectionLoadList.cpp b/lldb/source/Target/SectionLoadList.cpp index 45b6b52..598f49c 100644 --- a/lldb/source/Target/SectionLoadList.cpp +++ b/lldb/source/Target/SectionLoadList.cpp @@ -27,8 +27,9 @@ SectionLoadList::SectionLoadList(const SectionLoadList &rhs) } void SectionLoadList::operator=(const SectionLoadList &rhs) { - std::lock_guard lhs_guard(m_mutex); - std::lock_guard rhs_guard(rhs.m_mutex); + std::lock(m_mutex, rhs.m_mutex); + std::lock_guard lhs_guard(m_mutex, std::adopt_lock); + std::lock_guard rhs_guard(rhs.m_mutex, std::adopt_lock); m_addr_to_sect = rhs.m_addr_to_sect; m_sect_to_addr = rhs.m_sect_to_addr; } diff --git a/lldb/source/Target/ThreadList.cpp b/lldb/source/Target/ThreadList.cpp index 86248da..afdfda3 100644 --- a/lldb/source/Target/ThreadList.cpp +++ b/lldb/source/Target/ThreadList.cpp @@ -37,8 +37,10 @@ const ThreadList &ThreadList::operator=(const ThreadList &rhs) { if (this != &rhs) { // Lock both mutexes to make sure neither side changes anyone on us while // the assignment occurs - std::lock_guard guard(GetMutex()); - std::lock_guard rhs_guard(rhs.GetMutex()); + std::lock(GetMutex(), rhs.GetMutex()); + std::lock_guard guard(GetMutex(), std::adopt_lock); + std::lock_guard rhs_guard(rhs.GetMutex(), + std::adopt_lock); m_process = rhs.m_process; m_stop_id = rhs.m_stop_id;