diff -up Coro-5.25/Coro/Makefile.PL.ucontext Coro-5.25/Coro/Makefile.PL
--- Coro-5.25/Coro/Makefile.PL.ucontext 2011-01-10 11:29:04.000000000 +0100
+++ Coro-5.25/Coro/Makefile.PL 2011-01-10 11:29:18.000000000 +0100
@@ -49,7 +49,7 @@ if (exists $ENV{CORO_INTERFACE}) {
} elsif ($^O =~ /linux/) {
# everything "just works", as expected
- $iface = $iface_asm || "s";
+ $iface = $iface_asm || "u";
} elsif ($^O =~ /freebsd/) {
# FreeBSD 4.x has ucontext.h but no makecontext et al. (see BUGS section of