Merge patch from JeremyF:

33-pre_mutex_lock

HELGRIND: two updates: add a pre_mutex_lock tracking function, so the
skin can do something before the thread blocks. This allows us to do
lock ordering tests before the thread blocks in the deadlock we'd like
to report...


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@1306 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/include/vg_skin.h b/include/vg_skin.h
index 79d8471..540fe5f 100644
--- a/include/vg_skin.h
+++ b/include/vg_skin.h
@@ -1345,12 +1345,27 @@
 
 
       /* Mutex events (not exhaustive) */
+
+      /* Called before a thread can block while waiting for a mutex
+	 (called regardless of whether the thread will block or
+	 not) */
+      void (*pre_mutex_lock)    ( ThreadId tid, 
+                                  void* /*pthread_mutex_t* */ mutex );
+      /* Called once the thread actually holds the mutex (always
+	 paired with pre_mutex_lock) */
       void (*post_mutex_lock)   ( ThreadId tid, 
                                   void* /*pthread_mutex_t* */ mutex );
+      /* Called after a thread has released a mutex (no need for a
+	 corresponding pre_mutex_unlock, because unlocking can't
+	 block) */
       void (*post_mutex_unlock) ( ThreadId tid, 
                                   void* /*pthread_mutex_t* */ mutex );
 
+      /* Called during thread create, before the new thread has run
+	 any instructions (or touched any memory). */
       void (*post_thread_create)( ThreadId tid, ThreadId child );
+      /* Called once the joinee thread is terminated and the joining
+	 thread is about to resume. */
       void (*post_thread_join)  ( ThreadId joiner, ThreadId joinee );
       
       /* Others... thread, condition variable, signal events... */