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Modified patch from Piotr Rak that makes GetSharedModuleList() more thread safe and also fixed a missed member initialization on the copy contractor and also makes the assignment operator safer.

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llvm-svn: 204622
This commit is contained in:
Greg Clayton
2014-03-24 16:50:33 +00:00
parent d89b13625e
commit 1d77a8203b
1 changed files with 34 additions and 10 deletions
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44
lldb/source/Core/ModuleList.cpp
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@@ -10,6 +10,8 @@
#include "lldb/Core/ModuleList.h"
// C Includes
#include <stdint.h>
// C++ Includes
// Other libraries and framework includes
// Project includes
@@ -40,7 +42,8 @@ ModuleList::ModuleList() :
//----------------------------------------------------------------------
ModuleList::ModuleList(const ModuleList& rhs) :
m_modules(),
m_modules_mutex (Mutex::eMutexTypeRecursive)
m_modules_mutex (Mutex::eMutexTypeRecursive),
m_notifier(NULL)
{
Mutex::Locker lhs_locker(m_modules_mutex);
Mutex::Locker rhs_locker(rhs.m_modules_mutex);
@@ -62,9 +65,28 @@ ModuleList::operator= (const ModuleList& rhs)
{
if (this != &rhs)
{
Mutex::Locker lhs_locker(m_modules_mutex);
Mutex::Locker rhs_locker(rhs.m_modules_mutex);
m_modules = rhs.m_modules;
// That's probably me nit-picking, but in theoretical situation:
//
// * that two threads A B and
// * two ModuleList's x y do opposite assignemnts 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))
{
Mutex::Locker lhs_locker(m_modules_mutex);
Mutex::Locker rhs_locker(rhs.m_modules_mutex);
m_modules = rhs.m_modules;
}
else
{
Mutex::Locker rhs_locker(rhs.m_modules_mutex);
Mutex::Locker lhs_locker(m_modules_mutex);
m_modules = rhs.m_modules;
}
}
return *this;
}
@@ -832,13 +854,15 @@ ModuleList::GetIndexForModule (const Module *module) const
static ModuleList &
GetSharedModuleList ()
{
// NOTE: Intentionally leak the module list so a program doesn't have to
// cleanup all modules and object files as it exits. This just wastes time
// doing a bunch of cleanup that isn't required.
static ModuleList *g_shared_module_list = NULL;
if (g_shared_module_list == NULL)
g_shared_module_list = new ModuleList(); // <--- Intentional leak!!!
static std::once_flag g_once_flag;
std::call_once(g_once_flag, [](){
// NOTE: Intentionally leak the module list so a program doesn't have to
// cleanup all modules and object files as it exits. This just wastes time
// doing a bunch of cleanup that isn't required.
if (g_shared_module_list == NULL)
g_shared_module_list = new ModuleList(); // <--- Intentional leak!!!
});
return *g_shared_module_list;
}