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Protect DWARFCompileUnit::m_die_array by a new mutex 

Multiple DW_TAG_compile_unit being indexed in a multithreaded way can request
reading of the same DW_TAG_partial_unit.

Unfortunately one cannot detect DWZ file ahead of time to disable such locking
overhead as DWARFCompileUnit::Extract does not read the first DIE which is the
only place one could find early enough if the DWARF file is using any
DW_TAG_partial_unit.

Differential revision: https://reviews.llvm.org/D40470

llvm-svn: 331229
This commit is contained in:
Jan Kratochvil 2018-04-30 21:37:30 +00:00
parent 1934cb1c49
commit 32f2d0e564
2 changed files with 18 additions and 3 deletions
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19
lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp
View File

@ -41,9 +41,20 @@ DWARFUnit::~DWARFUnit() {}
// Parses a compile unit and indexes its DIEs if it hasn't already been done.
//----------------------------------------------------------------------
size_t DWARFUnit::ExtractDIEsIfNeeded(bool cu_die_only) {
const size_t initial_die_array_size = m_die_array.size();
if ((cu_die_only && initial_die_array_size > 0) || initial_die_array_size > 1)
return 0; // Already parsed
size_t initial_die_array_size;
auto already_parsed = [cu_die_only, &initial_die_array_size, this]() -> bool {
initial_die_array_size = m_die_array.size();
return (cu_die_only && initial_die_array_size > 0)
|| initial_die_array_size > 1;
};
{
llvm::sys::ScopedReader lock(m_extractdies_mutex);
if (already_parsed())
return 0;
}
llvm::sys::ScopedWriter lock(m_extractdies_mutex);
if (already_parsed())
return 0;
static Timer::Category func_cat(LLVM_PRETTY_FUNCTION);
Timer scoped_timer(
@ -304,6 +315,8 @@ void DWARFUnit::SetAddrBase(dw_addr_t addr_base,
void DWARFUnit::ClearDIEs(bool keep_compile_unit_die) {
if (m_die_array.size() > 1) {
llvm::sys::ScopedWriter lock(m_extractdies_mutex);
// std::vectors never get any smaller when resized to a smaller size, or
// when clear() or erase() are called, the size will report that it is
// smaller, but the memory allocated remains intact (call capacity() to see

2
lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h
View File

@ -13,6 +13,7 @@
#include "DWARFDIE.h"
#include "DWARFDebugInfoEntry.h"
#include "lldb/lldb-enumerations.h"
#include "llvm/Support/RWMutex.h"
class DWARFUnit;
class DWARFCompileUnit;
@ -160,6 +161,7 @@ protected:
// If this is a dwo compile unit this is the offset of the base compile unit
// in the main object file
dw_offset_t m_base_obj_offset = DW_INVALID_OFFSET;
llvm::sys::RWMutex m_extractdies_mutex;
static void
IndexPrivate(DWARFUnit *dwarf_cu, const lldb::LanguageType cu_language,