Commit 0ca59dd9 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar

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

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: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 3ddeb912
...@@ -85,7 +85,8 @@ static inline void native_write_msr(unsigned int msr, ...@@ -85,7 +85,8 @@ static inline void native_write_msr(unsigned int msr,
asm volatile("wrmsr" : : "c" (msr), "a"(low), "d" (high) : "memory"); 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) unsigned low, unsigned high)
{ {
int err; int err;
......
...@@ -2,6 +2,11 @@ ...@@ -2,6 +2,11 @@
# Makefile for x86-compatible CPU details and quirks # 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 := intel_cacheinfo.o addon_cpuid_features.o
obj-y += proc.o capflags.o powerflags.o common.o obj-y += proc.o capflags.o powerflags.o common.o
......
...@@ -287,7 +287,7 @@ static int __cpuinitdata unsafe_smp; ...@@ -287,7 +287,7 @@ static int __cpuinitdata unsafe_smp;
/* /*
* Activate a secondary processor. * 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 * Don't put *anything* before cpu_init(), SMP booting is too
......
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