commit 860b9ea0038cdcea2dda00b1657f945363c96d00
author Greg Clayton <gclayton@apple.com> Mon Apr 09 20:22:01 2012 +0000
committer Greg Clayton <gclayton@apple.com> Mon Apr 09 20:22:01 2012 +0000
tree adb808e26318d3b139b51cd7f9867cb8735540e7
parent 77147c2faa7339e04779df5c1e90db101a135fc3

<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.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@154339 91177308-0d34-0410-b5e6-96231b3b80d8

source/API/SBDebugger.cpp

diff --git a/source/API/SBDebugger.cpp b/source/API/SBDebugger.cpp
index b61acd7..4c62ffb 100644
--- a/source/API/SBDebugger.cpp
+++ b/source/API/SBDebugger.cpp
@@ -143,7 +143,12 @@
 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 @@
             result = m_opaque_sp->GetTargetList().DeleteTarget (target_sp);
             target_sp->Destroy();
             target.Clear();
-            ModuleList::RemoveOrphanSharedModules();
+            const bool mandatory = true;
+            ModuleList::RemoveOrphanSharedModules(mandatory);
         }
     }
 

source/Commands/CommandObjectTarget.cpp

diff --git a/source/Commands/CommandObjectTarget.cpp b/source/Commands/CommandObjectTarget.cpp
index 17d5fd5..ec48de6 100644
--- a/source/Commands/CommandObjectTarget.cpp
+++ b/source/Commands/CommandObjectTarget.cpp
@@ -520,7 +520,8 @@
             // 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);

source/Core/Module.cpp

diff --git a/source/Core/Module.cpp b/source/Core/Module.cpp
index 8ef4430..8932576 100644
--- a/source/Core/Module.cpp
+++ b/source/Core/Module.cpp
@@ -86,7 +86,8 @@
     void
     ClearModuleInfo (void)
     {
-        ModuleList::RemoveOrphanSharedModules();
+        const bool mandatory = true;
+        ModuleList::RemoveOrphanSharedModules(mandatory);
     }
     
     void

source/Core/ModuleList.cpp

diff --git a/source/Core/ModuleList.cpp b/source/Core/ModuleList.cpp
index 69245fb..5e4f660 100644
--- a/source/Core/ModuleList.cpp
+++ b/source/Core/ModuleList.cpp
@@ -112,9 +112,20 @@
 
 
 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 @@
 }
 
 uint32_t
-ModuleList::RemoveOrphanSharedModules ()
+ModuleList::RemoveOrphanSharedModules (bool mandatory)
 {
-    return GetSharedModuleList ().RemoveOrphans();    
+    return GetSharedModuleList ().RemoveOrphans(mandatory);
 }
 
 Error