From: Taylor R Campbell <campbell@mumble.net>
Date: Sun, 16 Nov 2014 18:53:28 +0000 (+0000)
Subject: Sternly advise against non-debugging use of THREAD-MUTEX-OWNER.
X-Git-Tag: mit-scheme-pucked-9.2.12~376^2~111
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=576ab7361f08756033e7e2c1a2f44ac74c233ad9;p=mit-scheme.git

Sternly advise against non-debugging use of THREAD-MUTEX-OWNER.
---

diff --git a/src/runtime/thread.scm b/src/runtime/thread.scm
index c9c766ffd..902bbcf1d 100644
--- a/src/runtime/thread.scm
+++ b/src/runtime/thread.scm
@@ -1048,6 +1048,12 @@ USA.
 	  (error "Don't own mutex:" mutex)
 	  (error "Don't own mutex:" mutex caller))))
 
+;;; Never use THREAD-MUTEX-OWNER except as a debugging feature.  If you
+;;; are tempted to make locking decisions on the basis of who owns a
+;;; mutex, fix your design so you're no longer tempted.  Mutexes are
+;;; non-recursive.  Use ASSERT-THREAD-MUTEX-OWNED to assert that you
+;;; own a mutex so you're less tempted to call THREAD-MUTEX-OWNER ever.
+
 (define (thread-mutex-owner mutex)
   (guarantee-thread-mutex mutex 'THREAD-MUTEX-OWNER)
   (thread-mutex/owner mutex))