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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>
This commit is contained in:
Ingo Molnar 2008-07-17 17:40:48 +02:00
parent c349e0a01c
commit 2464a609de
1 changed files with 5 additions and 12 deletions
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17
lib/Makefile
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@ -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