2011-07-28  Cary Coutant  <ccoutant@google.com>

	* workqueue-internal.h (Workqueue_threader::should_cancel_thread):
	Add thread_number parameter.
	(Workqueue_threader_threadpool::should_cancel_thread): Likewise.
	* workqueue-threads.cc
	(Workqueue_threader_threadpool::should_cancel_thread): Cancel
	current thread if its thread number is greater than desired thread
	count.
	* workqueue.cc (Workqueue_threader_single::should_cancel_thread):
	Add thread_number parameter.
	(Workqueue::should_cancel_thread): Likewise.
	(Workqueue::find_runnable_or_wait): Pass thread_number to
	should_cancel_thread.
	* workqueue.h (Workqueue::should_cancel_thread): Add thread_number
	parameter.


commit f380593e3f87ae9ba2e3ce6018bb5ee32797bfb8
Author: Cary Coutant <ccoutant@google.com>
Date:   Thu Jul 28 14:15:48 2011 -0700

    Fix race in thread cancellation.

diff --git a/gold/workqueue-internal.h b/gold/workqueue-internal.h
index 684c65b..764dc91 100644
--- a/gold/workqueue-internal.h
+++ b/gold/workqueue-internal.h
@@ -56,7 +56,7 @@ class Workqueue_threader
 
   // Return whether to cancel the current thread.
   virtual bool
-  should_cancel_thread() = 0;
+  should_cancel_thread(int thread_number) = 0;
 
  protected:
   // Get the Workqueue.
@@ -84,7 +84,7 @@ class Workqueue_threader_threadpool : public Workqueue_threader
 
   // Return whether to cancel a thread.
   bool
-  should_cancel_thread();
+  should_cancel_thread(int thread_number);
 
   // Process all tasks.  This keeps running until told to cancel.
   void
diff --git a/gold/workqueue-threads.cc b/gold/workqueue-threads.cc
index 60d4adc..de2ce5b 100644
--- a/gold/workqueue-threads.cc
+++ b/gold/workqueue-threads.cc
@@ -174,7 +174,7 @@ Workqueue_threader_threadpool::set_thread_count(int thread_count)
 // Return whether the current thread should be cancelled.
 
 bool
-Workqueue_threader_threadpool::should_cancel_thread()
+Workqueue_threader_threadpool::should_cancel_thread(int thread_number)
 {
   // Fast exit without taking a lock.
   if (!this->check_thread_count_)
@@ -182,12 +182,13 @@ Workqueue_threader_threadpool::should_cancel_thread()
 
   {
     Hold_lock hl(this->lock_);
-    if (this->threads_ > this->desired_thread_count_)
+    if (thread_number > this->desired_thread_count_)
       {
 	--this->threads_;
+	if (this->threads_ <= this->desired_thread_count_)
+	  this->check_thread_count_ = 0;
 	return true;
       }
-    this->check_thread_count_ = 0;
   }
 
   return false;
diff --git a/gold/workqueue.cc b/gold/workqueue.cc
index 6449bba..e78e86b 100644
--- a/gold/workqueue.cc
+++ b/gold/workqueue.cc
@@ -110,7 +110,7 @@ class Workqueue_threader_single : public Workqueue_threader
   { gold_assert(thread_count > 0); }
 
   bool
-  should_cancel_thread()
+  should_cancel_thread(int)
   { return false; }
 };
 
@@ -202,9 +202,9 @@ Workqueue::queue_next(Task* t)
 // Return whether to cancel the current thread.
 
 inline bool
-Workqueue::should_cancel_thread()
+Workqueue::should_cancel_thread(int thread_number)
 {
-  return this->threader_->should_cancel_thread();
+  return this->threader_->should_cancel_thread(thread_number);
 }
 
 // Find a runnable task in TASKS.  Return NULL if none could be found.
@@ -264,7 +264,7 @@ Workqueue::find_runnable_or_wait(int thread_number)
 	  return NULL;
 	}
 
-      if (this->should_cancel_thread())
+      if (this->should_cancel_thread(thread_number))
 	return NULL;
 
       gold_debug(DEBUG_TASK, "%3d sleeping", thread_number);
diff --git a/gold/workqueue.h b/gold/workqueue.h
index 9121e10..424b5e7 100644
--- a/gold/workqueue.h
+++ b/gold/workqueue.h
@@ -268,7 +268,7 @@ class Workqueue
 
   // Return whether to cancel this thread.
   bool
-  should_cancel_thread();
+  should_cancel_thread(int thread_number);
 
   // Master Workqueue lock.  This controls access to the following
   // member variables.