Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1479205
| From | Chunyan Zhang <zhang.lyra@gmail.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] arm64: use preempt_disable_notrace in _percpu_read/write |
| Date | 2016-09-08 15:20 +0200 |
| Message-ID | <sf7pf-6h3-7@gated-at.bofh.it> (permalink) |
| References | <sf6We-5Sk-1@gated-at.bofh.it> <sf7fA-6dR-15@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
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
>>
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH] arm64: use preempt_disable_notrace in _percpu_read/write Chunyan Zhang <zhang.chunyan@linaro.org> - 2016-09-08 14:50 +0200
Re: [PATCH] arm64: use preempt_disable_notrace in _percpu_read/write Mark Rutland <mark.rutland@arm.com> - 2016-09-08 15:10 +0200
Re: [PATCH] arm64: use preempt_disable_notrace in _percpu_read/write Chunyan Zhang <zhang.lyra@gmail.com> - 2016-09-08 15:20 +0200
Re: [PATCH] arm64: use preempt_disable_notrace in _percpu_read/write Will Deacon <will.deacon@arm.com> - 2016-09-09 12:10 +0200
Re: [PATCH] arm64: use preempt_disable_notrace in _percpu_read/write Chunyan Zhang <zhang.chunyan@linaro.org> - 2016-09-09 13:50 +0200
Re: [PATCH] arm64: use preempt_disable_notrace in _percpu_read/write Catalin Marinas <catalin.marinas@arm.com> - 2016-09-09 13:40 +0200
csiph-web