arm64: use preempt_disable_notrace in _percpu_read/write

When debug preempt or preempt tracer is enabled, preempt_count_add/sub()
can be traced by function and function graph tracing, and
preempt_disable/enable() would call preempt_count_add/sub(), so in Ftrace
subsystem we should use preempt_disable/enable_notrace instead.

In the commit 345ddcc882d8 ("ftrace: Have set_ftrace_pid use the bitmap
like events do") the function this_cpu_read() was added to
trace_graph_entry(), and if this_cpu_read() calls preempt_disable(), graph
tracer will go into a recursive loop, even if the tracing_on is
disabled.

So this patch change to use preempt_enable/disable_notrace instead in
this_cpu_read().

Since Yonghui Yang helped a lot to find the root cause of this problem,
so also add his SOB.

Signed-off-by: Yonghui Yang <mark.yang@spreadtrum.com>
Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
index 0a456bef8c792d91a30a4c2caf24cb6fb96546e2..2fee2f59288c94d70814771ed06fced11ede369d 100644 (file)
--- a/arch/arm64/include/asm/percpu.h
+++ b/arch/arm64/include/asm/percpu.h
@@ -199,19 +199,19 @@ static inline unsigned long __percpu_xchg(void *ptr, unsigned long val,
 #define _percpu_read(pcp)                                              \
 ({                                                                     \
        typeof(pcp) __retval;                                           \
-       preempt_disable();                                              \
+       preempt_disable_notrace();                                      \
        __retval = (typeof(pcp))__percpu_read(raw_cpu_ptr(&(pcp)),      \
                                              sizeof(pcp));             \
-       preempt_enable();                                               \
+       preempt_enable_notrace();                                       \
        __retval;                                                       \
 })
 
 #define _percpu_write(pcp, val)                                                \
 do {                                                                   \
-       preempt_disable();                                              \
+       preempt_disable_notrace();                                      \
        __percpu_write(raw_cpu_ptr(&(pcp)), (unsigned long)(val),       \
                                sizeof(pcp));                           \
-       preempt_enable();                                               \
+       preempt_enable_notrace();                                       \
 } while(0)                                                             \
 
 #define _pcp_protect(operation, pcp, val)                      \