Commit 2464a609 authored Jul 17, 2008 by Ingo Molnar

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>

parent c349e0a0

lib/Makefile

+5 −12

Original line number	Diff line number	Diff line
		@@ -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

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