condition variable implementation question

[Bruno Haible]

Hi Yoann, Ben, or anyone interested in threading,

Is this comment right or wrong?

In glibc's implementation of the wait and timed_wait methods for condition
variables, after returning from the blocking call, first the bookkeeping
in the condition variable is completed, then finally the lock is acquired
again.

In gnulib's gthread-win32.c it is the opposite: first the lock is taken,
then the bookkeeping is completed.

I think both implementations are right. OK to commit these comments?


2008-10-12  Bruno Haible  <address@hidden>

        * lib/glthread/cond.c (glthread_cond_wait_func,
        glthread_cond_timedwait_func): Add comments.

--- lib/glthread/cond.c.orig    2008-10-12 22:05:50.000000000 +0200
+++ lib/glthread/cond.c 2008-10-12 21:30:47.000000000 +0200
@@ -159,7 +159,8 @@
              break;
          }
 
-       /* Take the lock again.  */
+       /* Take the lock again.  It does not matter whether this is done
+          before or after the bookkeeping.  */
        err = glthread_lock_lock (lock);
 
        /* Do the bookkeeping.  */
@@ -285,7 +286,8 @@
              break;
          }
 
-       /* Take the lock again.  */
+       /* Take the lock again.  It does not matter whether this is done
+          before or after the bookkeeping.  */
        err = glthread_lock_lock (lock);
 
        /* Do the bookkeeping.  */