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tracing/ftrace: don't trace on early stage of a secondary cpu boot, v3

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Impact: fix a crash/hard-reboot on certain configs while enabling cpu runtime

On some archs, the boot of a secondary cpu can have an early fragile state.
On x86-64, the pda is not initialized on the first stage of a cpu boot but
it is needed to get the cpu number and the current task pointer. This data
is needed during tracing. As they were dereferenced at this stage, we got a
crash while tracing a cpu being enabled at runtime.

Some other archs like ia64 can have such kind of issue too.

Changes on v2:

We dropped the previous solution of a per-arch called function to guess the
current state of a cpu. That could slow down the tracing.

This patch removes the -pg flag on arch/x86/kernel/cpu/common.c where
the low level cpu boot functions exist, on start_secondary() and a helper
function used at this stage.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Frederic Weisbecker 2008-12-24 23:30:02 +01:00 committed by Ingo Molnar
parent 3ddeb912f4
commit 0ca59dd948
3 changed files with 8 additions and 2 deletions
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3
arch/x86/include/asm/msr.h
View file

@ -85,7 +85,8 @@ static inline void native_write_msr(unsigned int msr,
asm volatile("wrmsr" : : "c" (msr), "a"(low), "d" (high) : "memory");
}
static inline int native_write_msr_safe(unsigned int msr,
/* Can be uninlined because referenced by paravirt */
notrace static inline int native_write_msr_safe(unsigned int msr,
unsigned low, unsigned high)
{
int err;

5
arch/x86/kernel/cpu/Makefile
View file

@ -2,6 +2,11 @@
# Makefile for x86-compatible CPU details and quirks
#
# Don't trace early stages of a secondary CPU boot
ifdef CONFIG_FUNCTION_TRACER
CFLAGS_REMOVE_common.o = -pg
endif
obj-y := intel_cacheinfo.o addon_cpuid_features.o
obj-y += proc.o capflags.o powerflags.o common.o

2
arch/x86/kernel/smpboot.c
View file

@ -287,7 +287,7 @@ static int __cpuinitdata unsafe_smp;
/*
* Activate a secondary processor.
*/
static void __cpuinit start_secondary(void *unused)
notrace static void __cpuinit start_secondary(void *unused)
{
/*
* Don't put *anything* before cpu_init(), SMP booting is too