Generic semaphore implementation

Semaphores are no longer performance-critical, so a generic C
implementation is better for maintainability, debuggability and
extensibility.  Thanks to Peter Zijlstra for fixing the lockdep
warning.  Thanks to Harvey Harrison for pointing out that the
unlikely() was unnecessary.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>

arch/um/sys-ppc/Makefile

@@ -3,7 +3,7 @@ OBJ = built-in.o
 .S.o:
 	$(CC) $(KBUILD_AFLAGS) -D__ASSEMBLY__ -D__UM_PPC__ -c $< -o $*.o
 
-OBJS = ptrace.o sigcontext.o semaphore.o checksum.o miscthings.o misc.o \
+OBJS = ptrace.o sigcontext.o checksum.o miscthings.o misc.o \
 	ptrace_user.o sysrq.o
 
 EXTRA_AFLAGS := -DCONFIG_PPC32 -I. -I$(srctree)/arch/ppc/kernel
@@ -20,10 +20,6 @@ ptrace_user.o: ptrace_user.c
 sigcontext.o: sigcontext.c
 	$(CC) $(USER_CFLAGS) $(EXTRA_CFLAGS) -c -o $@ $<
 
-semaphore.c:
-	rm -f $@
-	ln -s $(srctree)/arch/ppc/kernel/$@ $@
-
 checksum.S:
 	rm -f $@
 	ln -s $(srctree)/arch/ppc/lib/$@ $@
@@ -66,4 +62,4 @@ misc.o: misc.S ppc_defs.h
 	$(CC) $(EXTRA_AFLAGS) $(KBUILD_AFLAGS) -D__ASSEMBLY__ -D__UM_PPC__ -c $< -o $*.o
 	rm -f asm
 
-clean-files := $(OBJS) ppc_defs.h checksum.S semaphore.c mk_defs.c
+clean-files := $(OBJS) ppc_defs.h checksum.S mk_defs.c