<rdar://problem/11202426>

Work around a deadlocking issue where "SBDebugger::MemoryPressureDetected ()" is being called and is causing a deadlock. We now just try and get the lock when trying to trim down the unique modules so we don't deadlock debugger GUI programs until we can find the root cause.

llvm-svn: 154339

5 files changed, 29 insertions, 10 deletions

diff --git a/lldb/include/lldb/Core/ModuleList.h b/lldb/include/lldb/Core/ModuleList.h
index 75d93c7c7ca..afe6dcb696f 100644
--- a/lldb/include/lldb/Core/ModuleList.h
+++ b/lldb/include/lldb/Core/ModuleList.h
@@ -356,7 +356,7 @@ public:
     Remove (ModuleList &module_list);
     
     size_t
-    RemoveOrphans ();
+    RemoveOrphans (bool mandatory);
 
     bool
     ResolveFileAddress (lldb::addr_t vm_addr,
@@ -418,7 +418,7 @@ public:
                        ModuleList &matching_module_list);
 
     static uint32_t
-    RemoveOrphanSharedModules ();
+    RemoveOrphanSharedModules (bool mandatory);
 
 protected:
     //------------------------------------------------------------------
diff --git a/lldb/source/API/SBDebugger.cpp b/lldb/source/API/SBDebugger.cpp
index b61acd75f62..4c62ffb2c02 100644
--- a/lldb/source/API/SBDebugger.cpp
+++ b/lldb/source/API/SBDebugger.cpp
@@ -143,7 +143,12 @@ SBDebugger::Destroy (SBDebugger &debugger)
 void
 SBDebugger::MemoryPressureDetected ()
 {
-    ModuleList::RemoveOrphanSharedModules();    
+    // Since this function can be call asynchronously, we allow it to be
+    // non-mandatory. We have seen deadlocks with this function when called
+    // so we need to safeguard against this until we can determine what is
+    // causing the deadlocks.
+    const bool mandatory = false;
+    ModuleList::RemoveOrphanSharedModules(mandatory);
 }
 
 SBDebugger::SBDebugger () :
@@ -648,7 +653,8 @@ SBDebugger::DeleteTarget (lldb::SBTarget &target)
             result = m_opaque_sp->GetTargetList().DeleteTarget (target_sp);
             target_sp->Destroy();
             target.Clear();
-            ModuleList::RemoveOrphanSharedModules();
+            const bool mandatory = true;
+            ModuleList::RemoveOrphanSharedModules(mandatory);
         }
     }
 
diff --git a/lldb/source/Commands/CommandObjectTarget.cpp b/lldb/source/Commands/CommandObjectTarget.cpp
index 17d5fd53b1c..ec48de6960d 100644
--- a/lldb/source/Commands/CommandObjectTarget.cpp
+++ b/lldb/source/Commands/CommandObjectTarget.cpp
@@ -520,7 +520,8 @@ public:
             // the global shared module list
             if (m_cleanup_option.GetOptionValue ())
             {
-                ModuleList::RemoveOrphanSharedModules();
+                const bool mandatory = true;
+                ModuleList::RemoveOrphanSharedModules(mandatory);
             }
             result.GetOutputStream().Printf("%u targets deleted.\n", (uint32_t)num_targets_to_delete);
             result.SetStatus(eReturnStatusSuccessFinishResult);
diff --git a/lldb/source/Core/Module.cpp b/lldb/source/Core/Module.cpp
index 8ef4430119c..89325762d48 100644
--- a/lldb/source/Core/Module.cpp
+++ b/lldb/source/Core/Module.cpp
@@ -86,7 +86,8 @@ namespace lldb {
     void
     ClearModuleInfo (void)
     {
-        ModuleList::RemoveOrphanSharedModules();
+        const bool mandatory = true;
+        ModuleList::RemoveOrphanSharedModules(mandatory);
     }
     
     void
diff --git a/lldb/source/Core/ModuleList.cpp b/lldb/source/Core/ModuleList.cpp
index 69245fb1a95..5e4f660dd28 100644
--- a/lldb/source/Core/ModuleList.cpp
+++ b/lldb/source/Core/ModuleList.cpp
@@ -112,9 +112,20 @@ ModuleList::Remove (const ModuleSP &module_sp)
 
 
 size_t
-ModuleList::RemoveOrphans ()
+ModuleList::RemoveOrphans (bool mandatory)
 {
-    Mutex::Locker locker(m_modules_mutex);
+    Mutex::Locker locker;
+    
+    if (mandatory)
+    {
+        locker.Reset (m_modules_mutex.GetMutex());
+    }
+    else
+    {
+        // Not mandatory, remove orphans if we can get the mutex
+        if (!locker.TryLock(m_modules_mutex.GetMutex()))
+            return 0;
+    }
     collection::iterator pos = m_modules.begin();
     size_t remove_count = 0;
     while (pos != m_modules.end())
@@ -587,9 +598,9 @@ ModuleList::FindSharedModules (const ModuleSpec &module_spec, ModuleList &matchi
 }
 
 uint32_t
-ModuleList::RemoveOrphanSharedModules ()
+ModuleList::RemoveOrphanSharedModules (bool mandatory)
 {
-    return GetSharedModuleList ().RemoveOrphans();    
+    return GetSharedModuleList ().RemoveOrphans(mandatory);
 }
 
 Error