Commit 2b974344 authored Sep 08, 2016 by Chunyan Zhang Committed by Catalin Marinas Sep 09, 2016

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 345ddcc8 ("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>

parent 872c63fb

arch/arm64/include/asm/percpu.h

+4 −4

Original line number	Diff line number	Diff line
		@@ -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) \