X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=base-target-features.lisp-expr;h=5b97f7295761437ba5dc5e439a4d482f78295d0e;hb=78e261f4ad7a0f3a0cf805ecc0052f0ccbf8fcd0;hp=6d10856ecace0093a6402a48786b789b6ac6415f;hpb=98a76d4426660876dec6649b1e228d2e5b47f579;p=sbcl.git

diff --git a/base-target-features.lisp-expr b/base-target-features.lisp-expr
index 6d10856..5b97f72 100644
--- a/base-target-features.lisp-expr
+++ b/base-target-features.lisp-expr
@@ -159,6 +159,15 @@
  ;; Note that no consistent effort to audit the SBCL library code for
  ;; thread safety has been performed, so caveat executor.
  ; :sb-thread
+
+ ;; Kernel support for futexes (so-called "fast userspace mutexes") is
+ ;; available in Linux 2.6 and some versions of 2.4 (Red Hat vendor
+ ;; kernels, possibly other vendors too).  We can take advantage of
+ ;; these to do faster and probably more reliable mutex and condition
+ ;; variable support.  An SBCL built with this feature will fall back
+ ;; to the old system if the futex() syscall is not available at
+ ;; runtime
+ ; :sb-futex
  
  ;; This affects the definition of a lot of things in bignum.lisp. It
  ;; doesn't seem to be documented anywhere what systems it might apply