Messages in this thread | | | From | Chunyan Zhang <> | Date | Thu, 8 Sep 2016 21:17:19 +0800 | Subject | Re: [PATCH] arm64: use preempt_disable_notrace in _percpu_read/write |
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Thanks Mark.
On 8 September 2016 at 21:02, Mark Rutland <mark.rutland@arm.com> wrote: > Hi, > > In future, please ensure that you include the arm64 maintainers when > sending changes to core arm64 code. I've copied Catalin and Will for you > this time.
Sorry about this.
Chunyan
> > Thanks, > Mark. > > On Thu, Sep 08, 2016 at 08:46:42PM +0800, Chunyan Zhang wrote: >> 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> >> --- >> arch/arm64/include/asm/percpu.h | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h >> index 0a456be..2fee2f5 100644 >> --- 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) \ >> -- >> 2.7.4 >> >> >> _______________________________________________ >> linux-arm-kernel mailing list >> linux-arm-kernel@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >>
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