From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S941363AbcIHNRW (ORCPT ); Thu, 8 Sep 2016 09:17:22 -0400 Received: from mail-qk0-f196.google.com ([209.85.220.196]:35894 "EHLO mail-qk0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933951AbcIHNRV (ORCPT ); Thu, 8 Sep 2016 09:17:21 -0400 MIME-Version: 1.0 In-Reply-To: <20160908130245.GD26570@leverpostej> References: <1473338802-18712-1-git-send-email-zhang.chunyan@linaro.org> <20160908130245.GD26570@leverpostej> From: Chunyan Zhang Date: Thu, 8 Sep 2016 21:17:19 +0800 Message-ID: Subject: Re: [PATCH] arm64: use preempt_disable_notrace in _percpu_read/write To: Mark Rutland Cc: Chunyan Zhang , Will Deacon , Catalin Marinas , rostedt@goodmis.org, mingo@redhat.com, mark.yang@spreadtrum.com, "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , takahiro.akashi@linaro.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thanks Mark. On 8 September 2016 at 21:02, Mark Rutland 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 >> Signed-off-by: Chunyan Zhang >> --- >> 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 >> From mboxrd@z Thu Jan 1 00:00:00 1970 From: zhang.lyra@gmail.com (Chunyan Zhang) Date: Thu, 8 Sep 2016 21:17:19 +0800 Subject: [PATCH] arm64: use preempt_disable_notrace in _percpu_read/write In-Reply-To: <20160908130245.GD26570@leverpostej> References: <1473338802-18712-1-git-send-email-zhang.chunyan@linaro.org> <20160908130245.GD26570@leverpostej> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Thanks Mark. On 8 September 2016 at 21:02, Mark Rutland 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 >> Signed-off-by: Chunyan Zhang >> --- >> 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 at lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >>