Throw something at the wall. See what sticks.

This is an attempt to fix or defer WorkerPoolMac pool stoppage.

1. Catch Objective-C exceptions thrown in task bodies.
2. Make sure the queue isn't suspended when posting tasks.

BUG=20471
TEST=none
Review URL: http://codereview.chromium.org/1699029

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@46124 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 28 insertions, 2 deletions

diff --git a/base/singleton_objc.h b/base/singleton_objc.h
index ba9fc78..3ba5f1e 100644
--- a/base/singleton_objc.h
+++ b/base/singleton_objc.h
@@ -23,7 +23,7 @@
 //     static Foo* New() {
 //       return [[Foo alloc] initWithName:@"selecty"];
 //     }
-//   }
+//   };
 //   ...
 //   Foo* widgetSingleton = SingletonObjC<Foo, FooSingletonTraits>::get();
 
diff --git a/base/worker_pool_mac.mm b/base/worker_pool_mac.mm
index 35d1079..9a9076e 100644
--- a/base/worker_pool_mac.mm
+++ b/base/worker_pool_mac.mm
@@ -11,6 +11,15 @@
 #import "base/singleton_objc.h"
 #include "base/task.h"
 
+// When C++ exceptions are disabled, the C++ library defines |try| and
+// |catch| so as to allow exception-expecting C++ code to build properly when
+// language support for exceptions is not present.  These macros interfere
+// with the use of |@try| and |@catch| in Objective-C files such as this one.
+// Undefine these macros here, after everything has been #included, since
+// there will be no C++ uses and only Objective-C uses from this point on.
+#undef try
+#undef catch
+
 namespace {
 
 Lock lock_;
@@ -75,7 +84,15 @@ size_t outstanding_ = 0;           // Operations posted but not completed.
 
   base::ScopedNSAutoreleasePool autoreleasePool;
 
-  task_->Run();
+  @try {
+    task_->Run();
+  } @catch(NSException* exception) {
+    LOG(ERROR) << "-[TaskOperation main] caught an NSException: "
+               << [[exception description] UTF8String];
+  } @catch(id exception) {
+    LOG(ERROR) << "-[TaskOperation main] caught an unknown exception";
+  }
+
   task_.reset(NULL);
 
   {
@@ -111,6 +128,15 @@ bool WorkerPool::PostTask(const tracked_objects::Location& from_here,
   NSOperationQueue* operation_queue = [WorkerPoolObjC sharedOperationQueue];
   [operation_queue addOperation:[TaskOperation taskOperationWithTask:task]];
 
+  if ([operation_queue isSuspended]) {
+    LOG(WARNING) << "WorkerPool::PostTask freeing stuck NSOperationQueue";
+
+    // Nothing should ever be suspending this queue, but in case it winds up
+    // happening, free things up.  This is a purely speculative shot in the
+    // dark for http://crbug.com/20471.
+    [operation_queue setSuspended:NO];
+  }
+
   // Periodically calculate the set of operations which have not made
   // progress and report how many there are.  This should provide a
   // sense of how many clients are seeing hung operations of any sort,