ftrace: do not trace library functions
make function tracing more robust: do not trace library functions.
We've already got a sizable list of exceptions:
ifdef CONFIG_FTRACE
# Do not profile string.o, since it may be used in early boot or vdso
CFLAGS_REMOVE_string.o = -pg
# Also do not profile any debug utilities
CFLAGS_REMOVE_spinlock_debug.o = -pg
CFLAGS_REMOVE_list_debug.o = -pg
CFLAGS_REMOVE_debugobjects.o = -pg
CFLAGS_REMOVE_find_next_bit.o = -pg
CFLAGS_REMOVE_cpumask.o = -pg
CFLAGS_REMOVE_bitmap.o = -pg
endif
... and the pattern has been that random library functionality showed
up in ftrace's critical path (outside of its recursion check), causing
hard to debug lockups.
So be a bit defensive about it and exclude all lib/*.o functions by
default. It's not that they are overly interesting for tracing purposes
anyway. Specific ones can still be traced, in an opt-in manner.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/lib/Makefile b/lib/Makefile
index d90d311..818c4d4 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -2,24 +2,17 @@
# Makefile for some libs needed in the kernel.
#
+ifdef CONFIG_FTRACE
+ORIG_CFLAGS := $(KBUILD_CFLAGS)
+KBUILD_CFLAGS = $(subst -pg,,$(ORIG_CFLAGS))
+endif
+
lib-y := ctype.o string.o vsprintf.o cmdline.o \
rbtree.o radix-tree.o dump_stack.o \
idr.o int_sqrt.o extable.o prio_tree.o \
sha1.o irq_regs.o reciprocal_div.o argv_split.o \
proportions.o prio_heap.o ratelimit.o
-ifdef CONFIG_FTRACE
-# Do not profile string.o, since it may be used in early boot or vdso
-CFLAGS_REMOVE_string.o = -pg
-# Also do not profile any debug utilities
-CFLAGS_REMOVE_spinlock_debug.o = -pg
-CFLAGS_REMOVE_list_debug.o = -pg
-CFLAGS_REMOVE_debugobjects.o = -pg
-CFLAGS_REMOVE_find_next_bit.o = -pg
-CFLAGS_REMOVE_cpumask.o = -pg
-CFLAGS_REMOVE_bitmap.o = -pg
-endif
-
lib-$(CONFIG_MMU) += ioremap.o
lib-$(CONFIG_SMP) += cpumask.o