From: Quanyang Wang <quanyang.wang@windriver.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Leo Yan <leo.yan@linaro.org>, Will Deacon <will@kernel.org>,
a.darwish@linutronix.de,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Paul Cercueil <paul@crapouillou.net>,
Randy Dunlap <rdunlap@infradead.org>,
ben.dooks@codethink.co.uk
Subject: Re: [PATCH V2] time/sched_clock: mark sched_clock_read_begin/retry as notrace
Date: Tue, 29 Sep 2020 16:09:15 +0800 [thread overview]
Message-ID: <3e9755ef-cf20-b5a6-455e-a11e110e6325@windriver.com> (raw)
In-Reply-To: <20200929074930.GG2611@hirez.programming.kicks-ass.net>
Hi Peter,
On 9/29/20 3:49 PM, Peter Zijlstra wrote:
> On Tue, Sep 29, 2020 at 09:50:51AM +0800, quanyang.wang@windriver.com wrote:
>> From: Quanyang Wang <quanyang.wang@windriver.com>
>>
>> Since sched_clock_read_begin and sched_clock_read_retry are called
>> by notrace function sched_clock, they shouldn't be traceable either,
>> or else ftrace_graph_caller will run into a dead loop on the path
>> as below (arm for instance):
>>
>> ftrace_graph_caller
>> prepare_ftrace_return
>> function_graph_enter
>> ftrace_push_return_trace
>> trace_clock_local
>> sched_clock
>> sched_clock_read_begin/retry
>>
>> Fixes: 1b86abc1c645 ("sched_clock: Expose struct clock_read_data")
>> Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>
>> ---
>> Changes:
>> V2: Add notrace to sched_clock_read_retry according to Peter's suggestion.
>>
>> kernel/time/sched_clock.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
>> index 1c03eec6ca9b..f629e3f5afbe 100644
>> --- a/kernel/time/sched_clock.c
>> +++ b/kernel/time/sched_clock.c
>> @@ -68,13 +68,13 @@ static inline u64 notrace cyc_to_ns(u64 cyc, u32 mult, u32 shift)
>> return (cyc * mult) >> shift;
>> }
>>
>> -struct clock_read_data *sched_clock_read_begin(unsigned int *seq)
>> +notrace struct clock_read_data *sched_clock_read_begin(unsigned int *seq)
>> {
>> *seq = raw_read_seqcount_latch(&cd.seq);
>> return cd.read_data + (*seq & 1);
>> }
>>
>> -int sched_clock_read_retry(unsigned int seq)
>> +int notrace sched_clock_read_retry(unsigned int seq)
>> {
>> return read_seqcount_retry(&cd.seq, seq);
>> }
> You're inconsistent in the placement of notrace, I prefer the first, the
> second read like notrace is the return type instead of a qualifier.
Thanks for your review. I will send a V3 patch to fix it.
Thanks,
Quanyang
>
> In any case,
>
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
prev parent reply other threads:[~2020-09-29 8:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-29 1:50 [PATCH V2] time/sched_clock: mark sched_clock_read_begin/retry as notrace quanyang.wang
2020-09-29 7:49 ` Peter Zijlstra
2020-09-29 8:09 ` Quanyang Wang [this message]
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