sh: Conditionalize gUSA support.
This conditionalizes gUSA support. gUSA is not supported on
SMP configurations, and it's not necessary there anyways due
to having other atomicity options (ie, movli.l/movco.l).
Anything implementing the LL/SC semantics (all SH-4A CPUs)
can switch to userspace atomicity implementations without
requiring gUSA. This is left default-enabled on all UP so
that glibc doesn't break.
Those that know what they are doing can disable this explicitly.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index a8693ed..44982c1 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -570,6 +570,20 @@
source "kernel/Kconfig.preempt"
+config GUSA
+ def_bool y
+ depends on !SMP
+ help
+ This enables support for gUSA (general UserSpace Atomicity).
+ This is the default implementation for both UP and non-ll/sc
+ CPUs, and is used by the libc, amongst others.
+
+ For additional information, design information can be found
+ in <http://lc.linux.or.jp/lc2002/papers/niibe0919p.pdf>.
+
+ This should only be disabled for special cases where alternate
+ atomicity implementations exist.
+
endmenu
menu "Boot options"